JP3551342B2

JP3551342B2 - Sealed battery

Info

Publication number: JP3551342B2
Application number: JP29871695A
Authority: JP
Inventors: 友康竹内
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 1995-11-16
Filing date: 1995-11-16
Publication date: 2004-08-04
Anticipated expiration: 2015-11-16
Also published as: JPH09139197A

Description

【０００１】
【発明の属する技術分野】
本発明は、防爆機能を備えた密閉型電池に関するものである。
【０００２】
【従来の技術】
近年、携帯機器用の電源として利用されているニッカドあるいはリチウムイオン等の電池では、外気中の水分等の混入による性能劣化や電池内容物の外部への漏出を防ぐため通常密閉構造がとられている。一方、化学電池においては機器の故障、誤使用等による短絡、過充電等の異常な電気的あるいは熱的な負荷が加えられた場合、電界液の分解や蒸発による多量のガスが発生し、密閉構造をとる電池ではガス発生による内圧上昇により容器の破裂が引き起こされるという問題がある。
【０００３】
この密閉型電池容器の破裂を防止する機構として内圧上昇時にガスを放出する弁構造が提案されている。例えば、特開平１−３０９２５２号公報、特開平１−３０９２５３号公報には、密閉容器の一部あるいは密閉容器の開口部を封口する封口体に切欠溝を形成し、容器に比べ耐圧強度が相対的に低くなるよう弁部を設けることで、内圧上昇時に弁部の開裂によりガスを放出する方法が開示されている。
【０００４】
また特開平４−３４９３４７号公報、特開平６−３６７５２号公報には、封口体を含む容器の一部に設けたガス放出孔を予めエッチング、プレス加工等の方法で弁部が形成された薄膜部品で封接することにより防爆用の弁構造を形成する方法が提案されている。
ところで上記の従来例の弁機構の作動圧力の設定にあたり、短絡や過充電時の電池容器の破裂を防止するためには、急激なガス発生に対し弁のガス放出が十分追従できることが必要である。したがって弁機構の作動圧力は電池容器の耐圧力に比べ十分低いことが望ましく、弁の安定した能力を発揮させるため通常の場合、開裂する溝あるいは弁部の肉厚は容器の肉厚の１／２０から１／１０程度の厚みで形成される必要がある。
【０００５】
ところがこのような弁部に溝加工をプレスまたはエッチング等の方法で形成する場合、通常では加工量が大きくなる程寸法バラツキも増加するため、溝加工の寸法誤差が生じ易く、その結果、弁の作動圧力にもバラツキが生じ、通常の使用状態においても弁が誤作動する場合があるという問題があった。
また弁部を形成する薄膜を封接する構造においては、膜厚を薄くする程低い圧力での弁の開裂が得られる傾向にあり、そのため薄膜に施す溝加工量も少なく設定できる。しかし、例えばレ−ザ溶接、かしめ等の方法でガス放出孔に接合する際に加えられる熱あるいは応力により、薄膜が薄い程歪が発生し易い。その結果弁の作動圧力が安定しないという問題があった。
【０００６】
【発明が解決しようとする課題】
本発明は従来の問題点に鑑み、電池内部の圧力が異常に上昇した場合には通気孔が開いて電池容器の破裂を確実に防ぎ、また通常の使用状況下では誤作動することのない信頼性の高い防爆構造を有する密閉型電池を提供することを目的とするものである。
【０００７】
【課題を解決するための手段】
本発明の密閉型電池は、起電力を有する化学物質を収納し長円状もしくは長方形状の通気孔をもつ容器本体と圧延方向が該通気孔の長手方向となりかつ該通気孔を気密的に塞ぐように該容器本体に固定された金属箔とで構成されていることを特徴とする。
【０００８】
本発明は金属箔はその圧延方向と直交する方向に引張応力が作用した場合比較的低いしかも一定した圧力で金属箔が破れるという発見に基づいている。圧延金属箔は圧延加工時に形成される圧延組織により圧延方向と直交する方向は機械的性質が圧延方向に比べ相対的にもろくなっている。したがって電池の内圧上昇時のように圧延金属箔の開裂は圧延方向に沿って起こり易い。このことから金属箔に形成される溝方向を箔の圧延方向に一致させること、あるいは、長円または長方形の通気孔の長手方向と圧延方向とを一致させることにより、従来の場合に比べ低圧力で防爆機能を作動させることができる。
【０００９】
本発明の密閉型電池は従来の密閉型電池と同様に密閉容器を有し、この密閉容器に起電力を有する化学物質が収納されている。この密閉容器は通気孔をもつ金属製容器本体とこの通気孔を塞ぐように気密的に固定された金属箔とで構成されている。
【００１２】
本発明の密閉型電池では、容器本体に設けられた通気孔は長円または長方形状であり、その通気孔の長手方向に圧延方向が一致した金属箔が通気孔を気密的に塞ぐように固定されている。なお、通気孔は金属製容器本体自体の内容積等に応じ任意の大きさとすることができる。
この金属箔に切欠溝を設けてもよい。切欠溝は圧延方向に沿って延びる１本の切欠溝とすることもできる。また、切欠溝は圧延方向に沿って延びる少なくとも１本の切欠溝とそれと交差する少なくとも１本の交差切欠溝とで形成することができる。この場合交差部分に亀裂が入り易く、溝の切欠感度が増し亀裂発生がより安定となる。
金属製容器の通気孔形状が長円もしくは長方形状であるので、内圧上昇時に金属箔に作用する引裂力は通気孔の短辺側よりも長辺側に沿って大きくなる。したがって金属箔の圧延方向を通気孔の長辺方向に一致させることにより金属箔の開裂をより低圧力で引起こすことが可能となる。もちろん、この場合においても圧延方向への溝の形成によって、更には圧延方向と直交する方向への溝の追加によって更に低圧力での防爆機能の作動を得ることも可能である。また特に長円もしくは長方形状の通気孔周縁にて金属箔が拘束固定されているので、通気孔短辺側拘束部と比べ長方形拘束部、特に長辺側拘束部の中心付近にて圧力作動時に金属箔への引裂力が作用し易いため、この部位近傍に溝を形成することがより有効である。具体的には、この金属箔はその通気孔の長手方向の周縁近くにそれぞれ１個、計２個の圧延方向に延びる切欠溝と、圧延方向に延びる各該切欠溝の中央部を結ぶ交差切欠溝をＨ字形に形成するのが好ましい。
本発明の金属箔は特に限定されないがその厚さが０．０２〜０．５ｍｍ、より実用的には０．０３〜０．５ｍｍが好ましい。また、金属箔はニッケル、アルミニウム、ステンレスあるいは銅製とすることができる。なお、金属箔の圧延方向とは最後に圧延されたときの方向を意味する。
【００１３】
切欠溝は通気孔の大きさに沿った長さとするのが良い。また、溝の深さは箔の厚さの１／１０〜９／１０程度、溝の幅は０．１〜０．５ｍｍ程度が実用的である。切欠溝はエツチング、プレス加工等で形成できる。
なお、通気孔を塞ぐように金属製容器本体に切欠溝をもつ金属箔を気密的に固定する方法としては、レーザビーム溶接、カシメ加工、溶材を用いた溶接等を採用できる。
【００１５】
【発明の作用】
本発明の密閉型電池では電池本体の通気孔が長円または長方形状でかつその長手方向と圧延方向が一致した金属箔が通気孔を塞いでいる。そして何らかの理由により電池内部の圧力が高まると金属箔はその圧力に押されダイヤフラム状に変形し、圧延方向と直交する方向により強く引張応力が作用する。圧延された金属箔は圧延方向と直交する方向に弱いため、圧延方向に延びる亀裂が生じ金属箔か破れる。そして電池内部の圧力はこの破れより外部に漏れ、電池内部の圧力が下がり、電池の爆発が阻止される。
更に、金属箔が切欠溝をもつ場合には、何らかの理由により電池内部の圧力が高まると切欠溝をもつ金属箔はその圧力に押されダイヤフラム状に変形し、切欠溝を開く方向に力が作用する。圧延された金属箔は圧延方向と直交する方向に弱いため、さらに切欠溝でその周囲よりもはるかに弱くなっているため切欠溝に亀裂が生じ金属箔か破れる。そして電池内部の圧力はこの破れより外部に漏れ、電池内部の圧力が下がり、電池の爆発が阻止される。
【００１６】
【試験例】
（試験例１）
試験例１の角形密閉型電池を以下に説明する。この角形密閉型電池は、その内部構成を簡略化した断面図を図１に示すように、電池容器１とこの容器内に封入された反応物２と絶縁体６により電池容器１と絶縁された正極を兼ねる外部端子４とこの外部端子４と反応物２とを電気的に接続するリード５とから構成されている。
【００１７】
電池容器１はステンレス鋼金属の厚さ０．５ｍｍの金属板で６面体状の箱形状に形成された負極を兼ねる容器本体１１と０．０５ｍｍのニッケル圧延箔で形成された弁部１５とからなる。容器本体１１の上端面には前記した外部端子４が固定されるとともに通気孔１ａが形成されている。この通気孔１ａは直径５ｍｍの円形に形成されている。
【００１８】
弁部１５はこの通気孔１ａを塞ぐように容器本体１１の内面にレ−ザ溶接により固定されている。この弁部１５はその弁部１５を含む角形密閉型電池の上から見た部分拡大図を図２に示すように、通気孔１ａの中央部に１本の切欠溝１５ａをもつ。なお、この弁部１５を形成する金属箔の圧延方向（矢印で示す）は切欠溝１５ａの延びる方向になっている。この切欠溝１５ａはその長さを４ｍｍ、幅０．２ｍｍ、深さ０．０３ｍｍで、化学エッチングにより形成したものである。なお、切欠溝１５ａの底の残肉厚は０．０２ｍｍとなっている。
【００１９】
本試験例１の角形密閉型電池は上記した構成からなる。この角形密閉型電池の電池容器１の機能を見るため、反応物２を封入していない電池容器１だけのものを別に１０個調製し、その内部に静水圧を加え、弁部１５が開く開裂圧力を測定した。これら１０個の開裂圧力の範囲は１４〜１６ｋｇ／ｃｍ² であった。なお、比較のために弁部１５の切欠溝１５ａを金属箔の圧延方向と直交する方向に形成した反応物２を封入していない電池容器だけの比較試料を同じように１０個調製し、その内部に静水圧を加え、弁部が開く開裂圧力を測定した。これら比較試料の１０個の開裂圧力の範囲は１９〜２２ｋｇ／ｃｍ² であった。
【００２０】
さらに他の比較試料として、金属箔の圧延方向と直交する切欠溝の深さを更に深くし、切欠溝の底の残肉厚を０．０１ｍｍとし、その他は試験例１の電池容器１と全く同じとしたものを１０個調製し、同じように開裂圧力を測定した。これら比較試料１０個の開裂圧力の範囲は１２〜１８ｋｇ／ｃｍ² であった。この切欠溝の底の残肉厚を０．０１ｍｍと薄くすることにより開裂圧力を低くすることができたが、開裂圧力のバラツキが大きくなり、またレ−ザ溶接による接合時に溝部に亀裂が生じてしまう場合があった。
【００２１】
試験例１の角形密閉型電池の電池容器１と２種類の比較例の電池容器の開裂圧力の測定より明らかなように、実施例１の電池容器１の場合には、切欠溝１５ａの底の残肉厚さが０．０２ｍｍと比較的厚い場合でも、その開裂圧力を１４〜１６ｋｇ／ｃｍ² と低く、かつそのバラツキを２ｋｇ／ｃｍ² の狭い範囲に収めることができた。
（試験例２）
本試験例２の角形密閉型電池の上から見た部分拡大図を図３に示す。この試験例２の角形密閉型電池は試験例１の角形密閉型電池とその弁部が異なるだけで、他の部分は試験例１のものと全く同じである。この試験例２の角形密閉型電池の弁部１６も試験例１の弁部１５と同じ０．０５ｍｍのニッケル圧延箔を用いた。試験例２の弁部１６は切欠溝として、圧延方向に沿った切欠溝１６ａとこれに直交する方向に設けた交差切欠溝１６ｂからなる十字形状の切欠溝をもつ。なお、これら２個の切欠溝１６ａ、１６ｂはいずれも長さを４ｍｍ、幅０．２ｍｍ、深さ０．０３ｍｍ、底の残肉厚０．０２ｍｍで、化学エッチングにより形成したものである。
【００２２】
なお、試験例２の弁部１６の開裂圧力は１２〜１５ｋｇ／ｃｍ² であった。前記例に比べ開裂圧力が低下する傾向が見られた。この開裂圧力は試験例１の弁部１５の開裂圧力１４〜１６ｋｇ／ｃｍ²より少し低いものであつた。尚、試験例１および試験例２において、弁部１５および弁部１６は電池容器１の内側位置にて封接した場合を示したが、電池内の圧力上昇時に弁部の変形が電池容器１の外側の部部品等により阻害されず、開裂圧力に影響を及ぼされない限りにおいて、弁部を電池容器１の外側位置にて封接しても一向に差し支えない。
（試験例３）
本発明の実施例にあたる試験例３の角形密閉型電池の上から見た部分拡大図を図４に示す。この試験例３の角形密閉型電池は試験例１の角形密閉型電池とその電池容器の容器本体の通気孔および弁部が異なるだけで、他の部分は試験例１のものと全く同じである。
【００２３】
この容器本体１１の通気孔１ｂは縦横それぞれ４ｍｍ、７ｍｍの長方形となっている。弁部１７はこの通気孔１ｂを塞ぐように容器本体１１の内面にレ−ザ溶接により固定されている。この弁部１７は通気孔１ｂの長手方向と圧延方向とを一致させた厚さ０．０５ｍｍのアルミ製の金属箔で形成されている。本実施例の角形密閉型電池は上記した構成からなる。この角形密閉型電池の電池容器１の機能を見るため、試験例１と同様に、電池容器１だけのものを別に１０個調製し、その内部に静水圧を加え、弁部１７が開く開裂圧力を測定した。これら１０個の開裂圧力の範囲は１３〜１６ｋｇ／ｃｍ² であった。
【００２４】
なお、比較のために弁部１７をその圧延方向が通気孔１ｂの長手方向と直交する方向としただけが異なり他は全く試験例３と同じにした電池容器だけの比較試料を同じように１０個調製し、その内部に静水圧を加え、弁部が開く開裂圧力を測定した。これら比較試料の１０個の開裂圧力の範囲は１５〜２０ｋｇ／ｃｍ²であった。
【００２５】
この試験例３より金属箔の圧延方向を容器本体の通気孔の長手方向と一致させることにより開裂圧力を１３〜１６ｋｇ／ｃｍ² と低くすることができた。尚、試験例１、２から明らかなように弁部１７をニッケルあるいはステンレス等の硬い材料で形成する場合に、図５のように金属箔を圧延方向に切欠溝１７ａを形成することにより、開裂圧力を低く、かつバラツキを少なくすることができる。
（試験例４）
本発明の実施例に当たる試験例４の角形密閉型電池の上から見た部分拡大図を図６に示す。この試験例４の角形密閉型電池は試験例３の角形密閉型電池とその弁部が異なるだけで、他の部分は試験例３のものと全く同じである。この試験例４の角形密閉型電池の弁部１８は０．０５ｍｍのニッケル圧延箔を用いた。
【００２６】
試験例４の弁部１８は切欠溝として、圧延方向に沿いかつ通気孔１ｂの長辺に沿った２個の切欠溝１８ａ、１８ａとこれに直交する方向に設けた交差切欠溝１８ｂからなるＨ字形状の切欠溝をもつ。なお、これら３個の切欠溝１８ａ、１８ａはいずれも長さを６ｍｍ、幅０．２ｍｍ、深さ０．０３ｍｍ、底の残肉厚０．０２ｍｍであり、交差切欠溝１８ｂは長さを４ｍｍ、幅０．２ｍｍ、深さ０．０３ｍｍ、底の残肉厚０．０２ｍｍであり、いずれも化学エッチングにより形成したものである。なお、試験例４の弁部１８の開裂圧力は１０〜１３ｋｇ／ｃｍ²であった。
【００２７】
本試験例の通気孔１ｂの長辺に沿った２個の切欠溝１８ａ、１８ａとこれに直交する方向に設けた交差切欠溝１８ｂからなるＨ字形状の切欠溝に代えて、図７に示すように通気孔１ｂの長辺の一方に沿った１個の切欠溝１８ａとこの切欠溝１８ａの中央から長辺の他方に伸びる１個の交差切欠溝１８ｂからなるＴ字形状の切欠溝としてもよい。
【００２８】
本発明の実施例にあたる試験例３、試験例４から明らかなように、通気孔の形状を長方形とし、その長手方向と圧延方向を一致させた金属箔で弁部を形成することにより、開裂圧力を低くかつバラツキの小さいものとすることができることがわかる。なお、試験例では通気孔に弁部を接合方法としてレ−ザ溶接を採用したが、両者の気密性及び接合強度を保てる限りにおいて、超音波溶接、接着等どのような接合方法を用いても構わない。また弁部に使用される材質は圧延材料であり、電蝕あるいは電池容器との接合性が使用上問題とならない限り、どのような材質を用いても良い。
【００２９】
また今回、電池容器を封接する封口体に通気孔を設ける例にて本発明を説明したが、電池容器に直接通気孔を設け、弁部にて閉塞するようにしてもよい。尚、従来例のように容器本体あるいはその封口体に直接弁部を設ける場合においても、容器本体あるいはその封口体が圧延金属で形成され、その圧延方向にそって切欠溝を形成してもよいことは明白である。
【００３０】
上記実施例に示すように、本発明によれば低圧力で再現性の良い防爆機能をもつ密閉電池が得られ、近年の携帯機器の携帯性の向上の要求による電池の軽量化への方向における電池容器の薄肉化での最小限の耐圧力保証が必要な状況にて本発明は非常に有効である。
【００３１】
【発明の効果】
本発明の密閉型電池ではその安全弁として使用する金属箔の膜厚化および形成される溝部の厚肉化が可能となる。そのため密閉容器への封接時の熱、外力等による歪の発生や溝加工時の寸法誤差を大幅に抑えることができ、加工が容易となる。また、低い圧力で再現性良く作動する防爆機能が得られ、かつ、通常使用時の誤作動による切欠溝の破れが防止できる。
【図面の簡単な説明】
【図１】比較例１の密閉型電池の断面図である。
【図２】比較例１の角形密閉型電池の弁部を示す上から見た部分拡大図である。
【図３】比較例２の角形密閉型電池の弁部を示す上から見た部分拡大図である。
【図４】本発明の実施例にあたる比較例３の角形密閉型電池の弁部を示す上から見た部分拡大図である。
【図５】本発明の比較例３の変形例にあたる角形密閉型電池の弁部を示す上から見た部分拡大図である。
【図６】本発明の比較例４の角形密閉型電池の弁部を示す上から見た部分拡大図である。
【図７】本発明の比較例４のの変形例にあたる角形密閉型電池の弁部を示す上から見た部分拡大図である。
【符号の説明】
１─電池容器２─反応物４─外部端子５─リード
６─絶縁体１１─容器本体１５、１６、１７、１８─弁部
１ａ、１ｂ─通気孔１５ａ、１６ａ、１７ａ、１８ａ─切欠溝
１６ｂ、１８ｂ─交差切欠溝[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sealed battery having an explosion-proof function.
[0002]
[Prior art]
In recent years, batteries such as nickel cadmium or lithium ion used as a power source for portable devices have usually adopted a sealed structure to prevent performance deterioration due to the incorporation of moisture in the outside air and leakage of battery contents to the outside. I have. On the other hand, in the case of chemical batteries, when abnormal electrical or thermal load such as short circuit due to equipment failure, misuse, etc., overcharge etc. is applied, a large amount of gas is generated due to decomposition and evaporation of the electrolytic solution, and the A battery having a structure has a problem that the container is ruptured due to an increase in internal pressure due to gas generation.
[0003]
As a mechanism for preventing the rupture of the sealed battery container, a valve structure that releases gas when the internal pressure rises has been proposed. For example, in JP-A-1-309252 and JP-A-1-309253, a notch groove is formed in a part of a sealed container or a sealing body for sealing an opening of the sealed container, and the pressure resistance is relatively higher than that of the container. A method is disclosed in which a valve portion is provided so as to be as low as possible, and when the internal pressure rises, gas is released by cleavage of the valve portion.
[0004]
Also, JP-A-4-349347 and JP-A-6-36952 disclose a thin film in which a gas release hole provided in a part of a container including a sealing body is formed with a valve portion by a method such as etching or pressing in advance. There has been proposed a method of forming an explosion-proof valve structure by sealing with parts.
By the way, in setting the operating pressure of the above-described conventional valve mechanism, in order to prevent a short circuit or bursting of the battery container at the time of overcharging, it is necessary that the gas release of the valve can sufficiently follow rapid gas generation. . Therefore, it is desirable that the operating pressure of the valve mechanism is sufficiently lower than the withstand pressure of the battery container. In order to exhibit the stable performance of the valve, the thickness of the groove to be cleaved or the valve portion is usually 1/1 / th of the thickness of the container. It must be formed with a thickness of about 20 to 1/10.
[0005]
However, when forming a groove in such a valve portion by a method such as pressing or etching, the dimensional variation generally increases as the processing amount increases, so that a dimensional error in the groove processing is likely to occur, and as a result, There is also a problem that the operating pressure varies, and the valve may malfunction even in a normal use state.
Further, in a structure in which the thin film forming the valve portion is sealed, the thinner the film thickness, the more likely the valve is to be cleaved at a lower pressure, so that the amount of groove processing performed on the thin film can be set smaller. However, the thinner the thin film, the more easily the strain is generated due to the heat or stress applied when joining to the gas discharge hole by a method such as laser welding or caulking. As a result, there is a problem that the operating pressure of the valve is not stabilized.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the conventional problems, and when the pressure inside the battery is abnormally increased, a vent hole is opened to reliably prevent the battery container from rupture, and a reliability that does not cause malfunction in a normal use condition. It is an object of the present invention to provide a sealed battery having a highly explosion-proof structure.
[0007]
[Means for Solving the Problems]
The sealed battery according to the present invention contains a chemical substance having an electromotive force and has a container body having an oblong or rectangular vent hole, and the rolling direction is the longitudinal direction of the vent hole, and the vent hole is airtightly closed. And a metal foil fixed to the container body as described above.
[0008]
The present invention is based on the discovery that the metal foil breaks at a relatively low and constant pressure when a tensile stress acts in a direction perpendicular to the rolling direction of the metal foil. The mechanical properties of the rolled metal foil in the direction perpendicular to the rolling direction are relatively brittle compared to the rolling direction due to the rolling structure formed during rolling. Therefore, as in the case where the internal pressure of the battery rises, cracking of the rolled metal foil tends to occur along the rolling direction. From this, by making the groove direction formed in the metal foil coincide with the rolling direction of the foil, or by making the longitudinal direction of the oblong or rectangular ventilation hole and the rolling direction coincide, the lower pressure than the conventional case is obtained. Can activate the explosion-proof function.
[0009]
The sealed battery of the present invention has a sealed container like a conventional sealed battery, and a chemical substance having an electromotive force is stored in the sealed container. This closed container is composed of a metal container main body having a vent and a metal foil which is hermetically fixed so as to close the vent.
[0012]
In the sealed battery of the present invention , the vent provided in the container body is oval or rectangular, and the metal foil whose rolling direction matches the longitudinal direction of the vent is fixed so as to hermetically close the vent. Have been. In addition, the ventilation hole can have an arbitrary size according to the internal volume of the metal container body itself.
Notch grooves may be provided in this metal foil. The notch groove may be a single notch groove extending along the rolling direction. Further, the notch groove can be formed by at least one notch groove extending along the rolling direction and at least one cross notch groove crossing the notch groove. In this case, a crack is easily formed at the intersection, the notch sensitivity of the groove is increased, and the crack generation is more stable.
Since the shape of the vent hole of the metal container is oval or rectangular, the tearing force acting on the metal foil when the internal pressure increases increases along the longer side than the shorter side of the vent. Therefore, by making the rolling direction of the metal foil coincide with the long side direction of the ventilation hole, it becomes possible to cause cleavage of the metal foil at a lower pressure. Of course, also in this case, it is possible to obtain the operation of the explosion-proof function at a lower pressure by forming grooves in the rolling direction and further by adding grooves in a direction perpendicular to the rolling direction. Also, since the metal foil is restrained and fixed especially at the periphery of the oval or rectangular vent hole, the rectangular restraint portion, especially the vicinity of the center of the long side restraint portion when the pressure is actuated compared with the short side restraint portion of the vent hole Since a tear force easily acts on the metal foil, it is more effective to form a groove near this portion. Specifically, this metal foil has two notch grooves extending in the rolling direction, one near each longitudinal edge of the ventilation hole, and a cross notch connecting the center of each notch groove extending in the rolling direction. Preferably, the groove is formed in an H shape.
The thickness of the metal foil of the present invention is not particularly limited, but is preferably 0.02 to 0.5 mm, more preferably 0.03 to 0.5 mm. The metal foil can be made of nickel, aluminum, stainless steel or copper. In addition, the rolling direction of the metal foil means the direction at the time of the last rolling.
[0013]
Preferably, the notch groove has a length along the size of the vent hole. It is practical that the depth of the groove is about 1/10 to 9/10 of the thickness of the foil, and the width of the groove is about 0.1 to 0.5 mm. The notch groove can be formed by etching, pressing, or the like.
In addition, as a method of airtightly fixing a metal foil having a notch groove to the metal container body so as to close the ventilation hole, laser beam welding, caulking, welding using a molten material, or the like can be adopted.
[0015]
Effect of the Invention
In the sealed battery according to the present invention , the vent hole of the battery main body has an oval or rectangular shape, and the metal foil whose rolling direction matches the longitudinal direction covers the vent hole. When the pressure inside the battery increases for some reason, the metal foil is pushed by the pressure and deforms into a diaphragm shape, and a tensile stress acts more strongly in a direction perpendicular to the rolling direction. Since the rolled metal foil is weak in a direction perpendicular to the rolling direction, a crack extending in the rolling direction is generated and the metal foil is broken. Then, the pressure inside the battery leaks to the outside due to the tear, and the pressure inside the battery drops, thereby preventing the battery from exploding.
Further, when the metal foil has a notch groove, if the pressure inside the battery increases for some reason, the metal foil having the notch groove is pressed by the pressure and deforms into a diaphragm shape, and a force acts in a direction to open the notch groove. I do. Since the rolled metal foil is weak in a direction orthogonal to the rolling direction, it is much weaker than its surroundings in the notch groove, so that the notch groove is cracked and the metal foil is broken. Then, the pressure inside the battery leaks to the outside due to the tear, and the pressure inside the battery drops, thereby preventing the battery from exploding.
[0016]
[Test example]
( Test Example 1)
The sealed rectangular battery of Test Example 1 will be described below. This rectangular sealed battery was insulated from the battery container 1 by a battery container 1, a reactant 2 sealed in the container, and an insulator 6, as shown in FIG. It comprises an external terminal 4 also serving as a positive electrode and a lead 5 for electrically connecting the external terminal 4 and the reactant 2.
[0017]
The battery container 1 is made up of a container body 11 serving as a negative electrode formed of a stainless steel metal plate having a thickness of 0.5 mm and having a hexahedral box shape and serving as a negative electrode, and a valve portion 15 formed of a 0.05 mm nickel rolled foil. Become. The external terminal 4 is fixed to the upper end surface of the container body 11 and a vent hole 1a is formed. This ventilation hole 1a is formed in a circular shape having a diameter of 5 mm.
[0018]
The valve portion 15 is fixed to the inner surface of the container body 11 by laser welding so as to close the ventilation hole 1a. As shown in FIG. 2 which is a partially enlarged view of the rectangular sealed battery including the valve portion 15 as viewed from above, the valve portion 15 has one notch groove 15a at the center of the vent 1a. The rolling direction (indicated by an arrow) of the metal foil forming the valve portion 15 is the direction in which the cutout groove 15a extends. The cutout groove 15a has a length of 4 mm, a width of 0.2 mm, and a depth of 0.03 mm, and is formed by chemical etching. The remaining thickness at the bottom of the cutout groove 15a is 0.02 mm.
[0019]
The sealed prismatic battery of Test Example 1 has the above-described configuration. In order to see the function of the battery container 1 of this rectangular sealed battery, another 10 battery containers 1 only containing no reactant 2 were prepared, hydrostatic pressure was applied to the inside, and the valve portion 15 was opened. The pressure was measured. The range of these ten cleavage pressures was 14-16 kg / cm ² . In addition, for comparison, ten comparative samples of only the battery container not enclosing the reactant 2 in which the cutout groove 15a of the valve portion 15 was formed in the direction perpendicular to the rolling direction of the metal foil were prepared in the same manner. Hydrostatic pressure was applied to the inside, and the cleavage pressure at which the valve opened was measured. The cleavage pressure range for the ten of these comparative samples was 19-22 kg / cm ² .
[0020]
As another comparative sample, the depth of the notch groove perpendicular to the rolling direction of the metal foil was further increased, the remaining thickness at the bottom of the notch groove was set to 0.01 mm, and the rest was completely the same as the battery container 1 of Test Example 1. Ten identical samples were prepared, and the cleavage pressure was measured in the same manner. The range of the cleavage pressure of these 10 comparative samples was 12 to 18 kg / cm ² . The cleavage pressure could be reduced by reducing the thickness of the bottom of the notch groove to 0.01 mm, but the variation in the cleavage pressure became large, and cracks occurred in the groove during joining by laser welding. There was a case.
[0021]
As is clear from the measurement of the breaking pressure of the battery case 1 of the square sealed type battery of the test example 1 and the battery case of the two comparative examples, in the case of the battery case 1 of the example 1, the bottom of the notch groove 15a even if the remaining wall thickness is relatively thick and 0.02 mm, lower the rupturing pressure force and 14~16kg / cm ^2, and was able to accommodate the variations in the narrow range of 2 kg / cm ^2.
( Test Example 2)
FIG. 3 shows a partially enlarged view of the square sealed battery of Test Example 2 as viewed from above. The prismatic sealed battery of Test Example 2 is different from the prismatic sealed battery of Test Example 1 only in the valve part, and the other parts are exactly the same as those of Test Example 1. For the valve portion 16 of the square sealed battery of Test Example 2, the same nickel rolled foil of 0.05 mm as the valve portion 15 of Test Example 1 was used. The valve portion 16 of Test Example 2 has, as the notch groove, a cross-shaped notch groove including a notch groove 16a along the rolling direction and a cross notch groove 16b provided in a direction orthogonal to the rolling direction. Each of these two notches 16a and 16b has a length of 4 mm, a width of 0.2 mm, a depth of 0.03 mm, and a bottom thickness of 0.02 mm, and is formed by chemical etching.
[0022]
In addition, the tearing pressure of the valve portion 16 in Test Example 2 was 12 to 15 kg / cm ² . There was a tendency for the cleavage pressure to be lower than in the above examples. This breaking pressure was slightly lower than the breaking pressure of the valve section 15 of Test Example 1 of 14 to 16 kg / cm ² . Note that in Test Example 1 and Test Example 2, the valve unit 15 and has a valve portion 16 shows a case in contact sealed at a position inside of the battery container 1, deformation battery case 1 of the valve portion when the pressure rise in the battery The valve unit may be sealed at a position outside the battery container 1 as long as it is not hindered by the external parts and the like and is not affected by the cleavage pressure.
( Test Example 3)
FIG. 4 is a partially enlarged view of the rectangular sealed battery of Test Example 3 as an example of the present invention, as viewed from above. In vents and the valve portion of the container body of the prismatic sealed battery of this test example 3 the prismatic sealed battery Test Example 1 that the battery container is different only other part is the same as that of Test Example 1 .
[0023]
The ventilation hole 1b of the container body 11 has a rectangular shape of 4 mm and 7 mm, respectively. The valve portion 17 is fixed to the inner surface of the container body 11 by laser welding so as to close the ventilation hole 1b. The valve portion 17 is made of a 0.05 mm-thick aluminum metal foil in which the longitudinal direction of the ventilation hole 1b and the rolling direction coincide with each other. The sealed rectangular battery according to the present embodiment has the above-described configuration. In order to see the function of the battery container 1 of this rectangular sealed battery, as in Test Example 1, another 10 battery containers 1 alone were prepared, hydrostatic pressure was applied to the inside thereof, and the tearing pressure at which the valve portion 17 was opened. Was measured. The range of these ten cleavage pressures was 13-16 kg / cm ² .
[0024]
For comparison, a comparative sample of only the battery container, which was the same as that of Test Example 3 except that the rolling direction of the valve portion 17 was perpendicular to the longitudinal direction of the vent hole 1b, was 10 Individual pieces were prepared, hydrostatic pressure was applied to the inside thereof, and the cleavage pressure at which the valve portion opened was measured. The breaking pressure range for the ten of these comparative samples was 15-20 kg / cm ² .
[0025]
By setting the rolling direction of the metal foil to coincide with the longitudinal direction of the vent hole of the container body, the tearing pressure could be reduced to 13 to 16 kg / cm ² from Test Example 3. When the valve portion 17 is formed of a hard material such as nickel or stainless steel as is apparent from Test Examples 1 and 2, the metal foil is split by forming the cutout grooves 17a in the rolling direction as shown in FIG. Pressure can be reduced and variation can be reduced.
( Test Example 4)
FIG. 6 is a partially enlarged view of a rectangular sealed battery of Test Example 4 corresponding to an example of the present invention as viewed from above. The square sealed battery of Test Example 4 is different from the square sealed battery of Test Example 3 only in the valve part, and the other parts are exactly the same as those of Test Example 3. For the valve section 18 of the sealed rectangular battery of Test Example 4, a nickel rolled foil of 0.05 mm was used.
[0026]
The valve portion 18 of Test Example 4 has, as a notch groove, an H formed by two notch grooves 18a, 18a along the rolling direction and along the long side of the ventilation hole 1b and a cross notch groove 18b provided in a direction perpendicular to the notch groove 18a. It has a U-shaped notch. Each of these three notches 18a, 18a has a length of 6 mm, a width of 0.2 mm, a depth of 0.03 mm, and a bottom remaining thickness of 0.02 mm, and the cross notch 18b has a length of 4 mm. , A width of 0.2 mm, a depth of 0.03 mm, and a bottom residual thickness of 0.02 mm, all of which were formed by chemical etching. In addition, the tearing pressure of the valve portion 18 in Test Example 4 was 10 to 13 kg / cm ² .
[0027]
Instead of the notched groove of the H-shape comprising a vent two notched grooves 18a along the long sides of the hole 1b, 18a and cross notched groove 18b provided in the direction perpendicular thereto of the present test example, shown in FIG. 7 As described above, a T-shaped notch formed by one notch 18a along one of the long sides of the ventilation hole 1b and one cross notch 18b extending from the center of the notch 18a to the other of the long sides may be used. Good.
[0028]
Example corresponding to Test Example 3 of the present invention, as is apparent from Test Example 4, the shape of the vent hole is rectangular, by forming the valve portion in the metal foil to match the rolling direction and the longitudinal direction, rupturing pressure force It can be seen that can be reduced and the variation is small. In the test examples , laser welding was adopted as a method of joining the valve portion to the vent hole. However, as long as the airtightness and joining strength of the two can be maintained, any joining method such as ultrasonic welding and adhesion can be used. I do not care. Further, the material used for the valve portion is a rolled material, and any material may be used as long as the electrolytic corrosion or the bonding property with the battery container does not cause a problem in use.
[0029]
In addition, although the present invention has been described with an example in which a ventilation hole is provided in a sealing body that seals a battery container, a ventilation hole may be directly provided in a battery container and closed by a valve. Incidentally, even in the case where the valve portion is provided directly on the container body or the sealing body thereof as in the conventional example, the container body or the sealing body may be formed of rolled metal, and the notch groove may be formed along the rolling direction. That is clear.
[0030]
As shown in the above embodiment, according to the present invention, a sealed battery having an explosion-proof function with good reproducibility at a low pressure can be obtained. The present invention is very effective in a situation where a minimum withstand pressure is required to be ensured by reducing the thickness of the battery container.
[0031]
【The invention's effect】
In the sealed battery of the present invention, the thickness of the metal foil used as the safety valve and the thickness of the formed groove can be increased. Therefore, generation of distortion due to heat, external force, and the like at the time of sealing to the closed container, and dimensional error at the time of groove processing can be significantly suppressed, and processing becomes easy. In addition, an explosion-proof function that operates with low pressure and good reproducibility can be obtained, and breakage of the notch groove due to malfunction during normal use can be prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a sealed battery of Comparative Example 1.
FIG. 2 is a partially enlarged view showing a valve portion of the prismatic sealed battery of Comparative Example 1 as viewed from above.
FIG. 3 is a partially enlarged view showing a valve portion of a sealed rectangular battery according to Comparative Example 2 as viewed from above.
FIG. 4 is a partially enlarged view showing a valve portion of a prismatic sealed battery of Comparative Example 3, which is an example of the present invention, as viewed from above.
FIG. 5 is a partially enlarged view showing a valve portion of a rectangular sealed battery according to a modification of Comparative Example 3 of the present invention, as viewed from above.
FIG. 6 is a partially enlarged view showing a valve portion of a prismatic sealed battery according to Comparative Example 4 of the present invention as viewed from above.
FIG. 7 is a partially enlarged view showing a valve portion of a rectangular sealed battery according to a modification of Comparative Example 4 of the present invention, as viewed from above.
[Explanation of symbols]
DESCRIPTION OF REFERENCE NUMERALS 1 battery case 2 reactant 4 external terminal 5 lead 6 insulator 11 container body 15, 16, 17, 18 valve portion 1a, 1b vent hole 15a, 16a, 17a, 18a notch groove 16b , 18b─Cross notch

Claims

In a sealed battery comprising a closed container having a container body containing a chemical substance having an electromotive force and having a vent and a thin film component which hermetically closes the vent, the vent is formed in an oval or rectangular shape. Wherein the thin-film component comprises a metal foil fixed to the container body such that the rolling direction is the longitudinal direction of the vent and the vent is hermetically closed. .

3. The sealed battery according to claim 2, wherein the metal foil further includes a notch groove extending in a rolling direction.

The metal foil has one or two notch grooves extending in the rolling direction near one or both sides in the longitudinal direction of the ventilation hole, and notch grooves intersecting at the center of each of the notch grooves. Item 7. A sealed battery according to Item 2 .

The sealed battery according to any one of claims 1 to 3 , wherein the metal foil has a thickness of 0.02 to 0.5 mm.

The sealed battery according to any one of claims 1 to 4 , wherein the metal foil is nickel, aluminum, stainless steel, or copper.