JP3759566B2

JP3759566B2 - Secondary battery

Info

Publication number: JP3759566B2
Application number: JP24945099A
Authority: JP
Inventors: 広一佐藤; 直哉中西; 一恭藤原; 俊之能間; 育郎米津
Original assignee: Sanyo Electric Co Ltd
Current assignee: Sanyo Electric Co Ltd
Priority date: 1998-09-03
Filing date: 1999-09-03
Publication date: 2006-03-29
Anticipated expiration: 2019-09-03
Also published as: JP2000149902A

Description

【０００１】
【発明の属する技術分野】
本発明は、電池缶の内部に巻き取り電極体等の二次電池要素を収容して、電池缶に取り付けられた一対の電極端子から二次電池要素の発生電力を取り出すことが可能な二次電池に関するものである。
【０００２】
【従来の技術】
近年、携帯型電子機器、電気自動車等の電源として、エネルギー密度の高いリチウム二次電池が注目されている。例えば電気自動車に用いられる比較的大きな容量の円筒型リチウム二次電池は、図１１及び図１２に示す様に、筒体(11)の両端部に蓋体(12)(12)を溶接固定してなる円筒状の電池缶(１)の内部に、巻き取り電極体(２)を収容して構成されている。両蓋体(12)(12)には、正負一対の電極端子機構(９)(９)が取り付けられており、巻き取り電極体(２)と両電極端子機構(９)(９)とが、複数本の集電タブ(３)により互いに接続されて、巻き取り電極体(２)が発生する電力を一対の電極端子機構(９)(９)から外部に取り出すことが可能となっている。又、蓋体(12)には圧力開閉式のガス排出弁(13)が取り付けられている。
【０００３】
巻き取り電極体(２)は、図１３に示す様に、リチウム複合酸化物を含む正極(21)と炭素材料を含む負極(23)の間に、非水電解液が含浸されたセパレータ(22)を介在させて、これらを渦巻き状に巻回して構成されている。
巻き取り電極体(２)の正極(21)及び負極(23)からは夫々複数本の集電タブ(３)が引き出され、極性が同じ複数本の集電タブ(３)の先端部(31)が１つの電極端子機構(９)に接続されている。尚、図１３においては、便宜上、一部の集電タブの先端部が電極端子機構(９)に接続されている状態のみを示し、他の集電タブについては、先端部が電極端子機構(９)に接続されている状態の図示を省略している。
【０００４】
電極端子機構(９)は、電池缶(１)の蓋体(12)を貫通して取り付けられたネジ部材(91)を具え、該ネジ部材(91)の基端部には鍔部(92)が形成されている。蓋体(12)の貫通孔には絶縁パッキング(93)が装着され、蓋体(12)と締結部材(91)の間の電気的絶縁性とシール性が保たれている。ネジ部材(91)には、筒体(11)の外側からワッシャ(94)が嵌められると共に、第１ナット(95)及び第２ナット(96)が螺合している。そして、第１ナット(95)を締め付けて、ネジ部材(91)の鍔部(92)とワッシャ(94)によって絶縁パッキング(93)を挟圧することにより、シール性を高めている。
前記複数本の集電タブ(３)の先端部(31)は、ネジ部材(91)の鍔部(92)に、スポット溶接或いは超音波溶接によって固定されている。
【０００５】
又、図９に示す如く蓋体(12)に開設した貫通孔(14)に、電池缶(１)の内圧が所定値を越えたときに作動する圧力開放型のガス排出弁(４)を取り付けた二次電池が知られている(特開平6-68861［H01M2-04］)。該ガス排出弁(４)は、図１０(ａ)に示す如く、リング体(41)に円板状の弁膜(42)を固定してなり、同図(ｂ)の如くリング体(41)の外周部が蓋体(12)の貫通孔(14)の開口縁にレーザ溶接(15)されて、蓋体(12)に固定されている。
【０００６】
【発明が解決しようとする課題】
しかしながら、大型の二次電池においては、数ｍｍ以上の厚さの大なる蓋体(12)にガス排出弁(４)をレーザ溶接によって固定する際、ガス排出弁(４)の厚さに対して蓋体(12)の厚さが非常に大きいために、溶接時の熱の放散が著しく、レーザビームを照射されて溶融した金属が急速に冷えることによって、溶接部にピンホールやクラック等の欠陥が生じる問題があった。
【０００７】
そこで本発明の目的は、ピンホールやクラックなどの欠陥を生じることなくガス排出のための弁(４)を蓋体(12)に溶接することが出来る二次電池を提供することである。
【０００８】
【課題を解決する為の手段】
本発明に係る二次電池は、筒体(11)の開口部に蓋体(12)が固定されて気密性を有する電池缶(１)の内部に、二次電池要素を収納して構成されている。蓋体(12)には、電池缶(１)の内圧が所定値を越えたときに開放する弁膜(42)と該弁膜 (42) の外周部に形成されたリング体 (41) とからなる円板状の弁(４)が、該リング体 (41) の外周部を蓋体(12)に開設された貫通孔(14)の開口縁にレーザ溶接して固定されている。又、蓋体(12)には、前記弁(４)の溶接部の周囲に、溶接時の熱が通過すべき熱流路の断面積を絞るための絞り部(51)が形成されている。
【０００９】
上記本発明の二次電池においては、前記弁(４)の溶接部の周囲に絞り部(51)が形成されているので、溶接時の熱は、先ず絞り部(51)に伝わった後、絞り部(51)の周囲に伝わり、放散されることになる。ここで絞り部(51)の熱容量は、蓋体(12)の全体に比べて極めて小さく、また熱流束が通過することとなる熱流路の断面積も、絞り部(51)内では小さなものとなるので、絞り部(51)が熱伝導抵抗となって、溶接時の熱の放散が抑制される。
この結果、溶接部は適度な速さで冷えて、ピンホールやクラックを生じることなく固化する。
【００１０】
具体的には、蓋体(12)の表面若しくは裏面に、前記弁(４)の溶接部を包囲して伸びる周溝(５)が凹設され、該周溝(５)の弁側の側面と前記弁(４)の溶接部との間に、前記絞り部(51)が形成されている。
又、他の具体的構成において、絞り部(51)は、蓋体(12)の表面に貫通孔(14)を包囲して突設した筒状の凸部(６)によって形成され、該凸部(６)の中央開口部に前記弁(４)が溶接固定されている。
【００１１】
尚、前記周溝(５)は、溝幅が蓋体(12)に開設された貫通孔(14)の内径の１／５０〜１の範囲であり、溝深さが蓋体(12)の厚さの２／３以下であることが望ましい。周溝(５)の溝幅が貫通孔(14)の内径の１／５０未満では、絞り部(51)の効果が低く、１を越えると、蓋体(12)の強度に問題が生じる。又、溝深さが蓋体(12)の厚さの２／３を越えると、蓋体(12)の強度に問題が生じる。
【００１２】
二次電池は、例えば電池容量が５Ａｈ以上、２００Ａｈ以下であり、蓋体(12)の厚さが１〜５ｍｍである。この様な大型の二次電池において、従来はガス排出弁の溶接部からの熱放散が著しく、本発明の絞り部(51)が優れた効果を発揮する。
【００１３】
【発明の効果】
本発明に係る二次電池によれば、蓋体(12)に絞り部(51)を形成することによって、蓋体(12)に前記弁(４)を溶接する際の熱の放散が抑制され、溶接時に溶融した金属が適度な速度で冷えるので、溶接部にピンホールやクラックなどの欠陥を生じることはない。
【００１４】
【発明の実施の形態】
以下、本発明を図１１乃至図１３に示す大型のリチウム二次電池(電池容量５Ａｈ〜２００Ａｈ)に実施した形態につき、図面に沿って具体的に説明する。尚、図１１乃至図１３に示す二次電池と同一の構成要素については、同一の符号を付して説明を省略する。
【００１５】
第１実施例
本実施例の二次電池においては、図１に示す如く、電池缶(１)を構成する蓋体(12)に貫通孔(14)を開設すると共に、該貫通孔(14)を塞いでガス排出弁(４)を溶接固定している。又、蓋体(12)の表面には、ガス排出弁(４)を包囲して、周溝(５)が凹設され、該周溝(５)とガス排出弁(４)の間に、絞り部(51)を形成している。
【００１６】
ガス排出弁(４)は、図２(ａ)に示す如く円環状のリング体(41)に円板状の弁膜(42)を固定してなる。一方、蓋体(12)に開設された貫通孔(14)は、該ガス排出弁(４)が係合可能な段付き溝に形成されている。
ガス排出弁(４)は、同図(ｂ)に示す如く蓋体(12)の貫通孔(14)に装着された状態で、リング体(41)の外周部を蓋体(12)にレーザ溶接して固定される。
【００１７】
この際、蓋体(12)の表面には、ガス排出弁(４)の溶接部(15)を包囲して、円環状の絞り部(51)が形成されているので、溶接時の熱は、先ず絞り部(51)に伝わった後、絞り部(51)の周囲に伝わり、放散される。従って、絞り部(51)が熱伝導抵抗となって、溶接時の熱の放散が抑制される。この結果、溶融状態の溶接部(15)は徐々に冷却されて、クラックやピンホールなどの欠陥を生じることなく、ガス排出弁(４)が蓋体(12)に溶接固定される。
【００１８】
尚、本実施例において、蓋体(12)はアルミニウム製であって、図３に示す如く、外径Ｅが６０ｍｍ、厚さＦが４ｍｍ、厚さＴが１.０ｍｍ、蓋体(12)の内径Ｈが７ｍｍ、ガス排出弁(４)の外径Ｄが９ｍｍ、周溝(５)の内周面の径Ａが１１ｍｍ、外周面の径Ｂが１３ｍｍ、周溝(５)の溝幅Ｃが１ｍｍ、溝深さＧが１.５ｍｍに設定されている。
【００１９】
上記本発明の二次電池における効果を実証するべく、蓋体(12)に絞り部(51)を具えた本発明の電池缶と、絞り部(51)を具えない比較例としての電池缶について、それぞれ１０枚の蓋体を作成し、窒素ガスによるリークチェックと、ガス排出弁の作動圧のチェックを行なった。その結果を表１に示す。尚、リークチェックは、３Ｋｇ／ｃｍ²の窒素ガスによって加圧を行ない、石鹸液によってリークの有無を調べた。又、ガス排出弁は、弁単体としての作動圧の仕様が８±１Ｋｇ／ｃｍ²のものを採用した。
【００２０】
【表１】

【００２１】
表１の結果から明らかな様に、本発明の蓋体においては、何れもリークは認められず、作動圧も仕様の値が得られた。これに対し、比較例では、４枚の蓋体についてピンホールやクラックが発生し、３枚の蓋体について、ガス排出弁の作動圧に低下が認められた。ピンホールやクラックの原因としては、レーザ溶接時の熱の放散が著しいために、溶接部の温度低下が急激となったことが考えられる。又、作動圧の低下の原因としては、レーザ溶接時の熱の放散が著しいために、溶接時間が過度に長くなって、ガス排出弁(４)の弁膜(42)に熱がかかり過ぎ、熱応力によって弁膜(42)が変形し、局所的に薄肉部が生じたことが考えられる。
【００２２】
又、本発明の蓋体(図４(ａ))と、絞り部(51)を具えない従来の蓋体(同図(ｂ))について、ガス排出弁(４)をレーザ溶接した直後(５秒後、２０秒後)の蓋体(12)の各部の温度をサーモグラフィによって測定した。その結果を表２及び表３に示す。尚、表中の測定場所Ｎｏ．は、図４(ａ)(ｂ)に示す番号位置に対応している。
【００２３】
【表２】

【表３】

【００２４】
従来の蓋体では、溶接時の熱放散が著しく、溶接後の温度低下が急激なものとなっており、これによって、上述の如く溶接部にピンホールやクラックが発生するのである。
これに対し、本発明の蓋体では、熱流路の絞り部が形成されているために、溶接後の温度低下が比較的小さなものとなっており、これによって、上述の如くピンホールやクラックを発生させることなく、ガス排出弁を溶接することが出来るのである。
【００２５】
更に上記本発明の二次電池において、周溝(５)の溝幅の最適範囲を調べるべく、直径６０ｍｍ、厚さ４.１ｍｍを有すると共に、内径１０ｍｍの貫通孔(14)と深さ１.５ｍｍの周溝(５)とが形成された本発明の蓋体であって、周溝(５)が種々の溝幅を有する蓋体を作製して、ガス排出弁溶接後５秒後の温度測定と、３Ｋｇ／ｃｍ²の窒素ガスによるリークチェックとを行なった。
又、各蓋体と同一寸法の周溝(５)のみを凹設して、貫通孔(14)のない蓋体を作製し、これらの蓋体について、２０Ｋｇ／ｃｍ²の窒素ガスによるリークチェックと、蓋体の変形及び歪みの有無を水準計で確認した。その結果を表４に示す。
【００２６】
【表４】

【００２７】
表４の結果から明らかな様に、周溝(５)の幅が貫通孔(14)の内径の１／５０よりも小さくなると、溶接部近傍の温度低下が著しく、これによってピンホールが発生したものである。又、周溝(５)の幅が貫通孔(14)の内径よりも大きくなると、蓋体(12)の強度が極端に低下して、所定の圧力(２０Ｋｇ／ｃｍ²)に耐えることが出来ない。従って、周溝(５)の溝幅は、蓋体(12)の貫通孔(14)の内径Ｈの１／５０〜１の範囲が望ましいと言える。
【００２８】
又、上記本発明の二次電池において、周溝(５)の深さの最適範囲を調べるべく、周溝(５)が幅１ｍｍであって、種々の溝深さを有すると共に、その他は上記と同一寸法を有する蓋体を作製して、同様の耐圧試験を行なった。その結果を表５に示す。
【００２９】
【表５】

【００３０】
表５の結果から明らかな様に、周溝(５)の深さが蓋体(12)の厚さＦの２／３を越えると、蓋体(12)の強度に問題が生じる。従って、周溝(５)の深さは、蓋体(12)の厚さＦの２／３以下が望ましいと言える。
【００３１】
第２実施例
本実施例の二次電池は、図５に示す如く、蓋体(12)の表面に、貫通孔(14)を包囲して、円筒状の凸部(６)を突設し、該凸部(６)の中央開口部にガス排出弁(４)を溶接固定したものである。該二次電池においては、凸部(６)が前記絞り部(51)となって、溶接部(15)の熱の放散を抑制する。
【００３２】
第３実施例
本実施例の二次電池は、図６に示す如く、第２実施例の凸部(６)の周囲に、第１実施例の周溝(５)を凹設したものである。
【００３３】
第４実施例
本実施例の二次電池は、図７に示す如く、蓋体(12)の裏面に、第１実施例と同様の周溝(５)を凹設したものである。該二次電池においては、周溝(５)の底面と蓋体(12)表面の間に前記絞り部(51)が形成されることになる。
【００３４】
第５実施例
本実施例の二次電池は、図８に示す如く、周溝(５)が第１実施例の如く連続したものではなく、１或いは複数箇所で途切れた断続的な周溝(５)を具えたものである。これら複数の周溝(５)に代えて、多数の円孔を円陣に配設することも可能である。
上記第２〜第５実施例の何れにおいても、上記第１実施例の二次電池と同様の効果が得られるのは言うまでもない。
【図面の簡単な説明】
【図１】本発明に係る第１実施例の二次電池の要部を示す断面図である。
【図２】該二次電池において、蓋体にガス排出弁を溶接固定する工程(ａ)(ｂ)を表わす断面図である。
【図３】蓋体の各部寸法を表わす断面図である。
【図４】本発明の蓋体(ａ)と比較例(ｂ)の蓋体において、温度測定場所を示す図である。
【図５】第２実施例の蓋体の断面図である。
【図６】第３実施例の蓋体の断面図である。
【図７】第４実施例の蓋体の断面図である。
【図８】第５実施例の蓋体に凹設された複数の周溝の平面図である。
【図９】従来の圧力開放型のガス排出弁を具えた二次電池の要部を示す断面図である。
【図１０】該二次電池において、蓋体にガス排出弁を溶接固定する工程(ａ)(ｂ)を表わす断面図である。
【図１１】従来の圧力開閉式のガス排出弁を具えた円筒型リチウム二次電池の斜視図である。
【図１２】該二次電池の分解斜視図である。
【図１３】該二次電池の要部を表わす断面図である。
【符号の説明】
(１) 電池缶
(11) 筒体
(12) 蓋体
(14) 貫通孔
(４) ガス排出弁
(41) リング体
(42) 弁膜
(５) 周溝
(51) 絞り部
(６) 凸部[0001]
BACKGROUND OF THE INVENTION
The present invention accommodates a secondary battery element such as a wound electrode body inside a battery can, and a secondary battery capable of taking out the generated power of the secondary battery element from a pair of electrode terminals attached to the battery can. It relates to batteries.
[0002]
[Prior art]
In recent years, lithium secondary batteries with high energy density have attracted attention as power sources for portable electronic devices and electric vehicles. For example, as shown in FIGS. 11 and 12, a cylindrical lithium secondary battery with a relatively large capacity used in an electric vehicle has lids (12) and (12) fixed to both ends of a cylindrical body (11) by welding. The take-up electrode body (2) is accommodated in the cylindrical battery can (1). A pair of positive and negative electrode terminal mechanisms (9), (9) is attached to the lid bodies (12), (12), and the winding electrode body (2) and the both electrode terminal mechanisms (9), (9) are provided. The electric power generated by the winding electrode body (2) connected to each other by a plurality of current collecting tabs (3) can be taken out from the pair of electrode terminal mechanisms (9), (9). . Further, a pressure open / close type gas discharge valve (13) is attached to the lid (12).
[0003]
As shown in FIG. 13, the wound electrode body (2) includes a separator (22) impregnated with a non-aqueous electrolyte between a positive electrode (21) containing a lithium composite oxide and a negative electrode (23) containing a carbon material. ), And these are spirally wound.
A plurality of current collecting tabs (3) are drawn out from the positive electrode (21) and the negative electrode (23) of the winding electrode body (2), respectively, and the tips (31) of the plurality of current collecting tabs (3) having the same polarity are drawn out. ) Is connected to one electrode terminal mechanism (9). In FIG. 13, for the sake of convenience, only the state where the tip portions of some of the current collecting tabs are connected to the electrode terminal mechanism (9) is shown. Illustration of the state connected to 9) is omitted.
[0004]
The electrode terminal mechanism (9) includes a screw member (91) attached through the lid (12) of the battery can (1), and a hook (92) is provided at the base end of the screw member (91). ) Is formed. An insulating packing (93) is attached to the through hole of the lid (12), and electrical insulation and sealing between the lid (12) and the fastening member (91) are maintained. A washer (94) is fitted to the screw member (91) from the outside of the cylindrical body (11), and a first nut (95) and a second nut (96) are screwed together. The first nut (95) is tightened and the insulating packing (93) is clamped by the flange (92) and the washer (94) of the screw member (91), thereby improving the sealing performance.
The tip portions (31) of the plurality of current collecting tabs (3) are fixed to the flange portion (92) of the screw member (91) by spot welding or ultrasonic welding.
[0005]
Further, as shown in FIG. 9, a pressure release type gas discharge valve (4) that operates when the internal pressure of the battery can (1) exceeds a predetermined value is provided in the through hole (14) opened in the lid (12). An attached secondary battery is known (Japanese Patent Laid-Open No. 6-68861 [H01M2-04]). As shown in FIG. 10 (a), the gas discharge valve (4) is formed by fixing a disc-shaped valve membrane (42) to a ring body (41), and the ring body (41) as shown in FIG. 10 (b). The outer peripheral portion is laser welded (15) to the opening edge of the through hole (14) of the lid (12) and fixed to the lid (12).
[0006]
[Problems to be solved by the invention]
However, in a large-sized secondary battery, when the gas discharge valve (4) is fixed to the large lid (12) with a thickness of several mm or more by laser welding, the thickness of the gas discharge valve (4) The thickness of the lid (12) is very large, so the heat dissipation during welding is significant, and the molten metal irradiated with the laser beam cools rapidly, causing pinholes and cracks in the weld. There was a problem that caused defects.
[0007]
Accordingly, an object of the present invention is to provide a secondary battery in which a valve (4) for gas discharge can be welded to a lid (12) without causing defects such as pinholes and cracks.
[0008]
[Means for solving the problems]
A secondary battery according to the present invention is configured by accommodating a secondary battery element in a battery can (1) having a lid (12) fixed to an opening of a cylindrical body (11) and having airtightness. ing. The lid (12), consisting of an open and leaflet (42) ring members formed on an outer peripheral portion of the valve membrane (42) and (41) when the internal pressure of the battery can (1) exceeds a predetermined value A disc-shaped valve (4) is fixed by laser welding the outer periphery of the ring body (41) to the opening edge of the through hole (14) formed in the lid body (12). The lid (12) is formed with a constriction (51) for constricting the cross-sectional area of the heat flow path through which heat at the time of welding passes, around the weld of the valve (4).
[0009]
In the secondary battery of the present invention, since the throttle part (51) is formed around the welded part of the valve (4), the heat during welding is first transmitted to the throttle part (51), It is transmitted to the periphery of the throttle part (51) and is dissipated. Here, the heat capacity of the throttle part (51) is extremely small compared to the entire cover (12), and the cross-sectional area of the heat flow path through which the heat flux passes is also small in the throttle part (51). Therefore, the throttle part (51) serves as a heat conduction resistance, and heat dissipation during welding is suppressed.
As a result, the welded portion cools at an appropriate speed and solidifies without causing pinholes or cracks.
[0010]
Specifically, a circumferential groove (5) extending so as to surround the welded portion of the valve (4) is formed on the front or back surface of the lid (12), and the side surface on the valve side of the circumferential groove (5). The throttle part (51) is formed between the valve and the welded part of the valve (4).
In another specific configuration, the throttle part (51) is formed by a cylindrical convex part (6) projecting from the surface of the lid (12) so as to surround the through hole (14). The valve (4) is fixed by welding to the central opening of the portion (6).
[0011]
The circumferential groove (5) has a groove width in the range of 1/50 to 1 of the inner diameter of the through hole (14) provided in the lid (12), and the groove depth of the lid (12). It is desirable that it is 2/3 or less of the thickness. If the groove width of the circumferential groove (5) is less than 1/50 of the inner diameter of the through hole (14), the effect of the throttle part (51) is low, and if it exceeds 1, the strength of the lid (12) will be problematic. Further, when the groove depth exceeds 2/3 of the thickness of the lid (12), a problem occurs in the strength of the lid (12).
[0012]
The secondary battery has, for example, a battery capacity of 5 Ah or more and 200 Ah or less, and a thickness of the lid (12) of 1 to 5 mm. In such a large-sized secondary battery, heat dissipation from the welded portion of the gas exhaust valve has been significant in the past, and the throttle portion (51) of the present invention exhibits an excellent effect.
[0013]
【The invention's effect】
According to the secondary battery of the present invention, by forming the throttle part (51) in the lid (12), heat dissipation when the valve (4) is welded to the lid (12) is suppressed. Since the molten metal at the time of welding cools at an appropriate speed, defects such as pinholes and cracks do not occur in the welded portion.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention applied to a large-sized lithium secondary battery (battery capacity 5 Ah to 200 Ah) shown in FIGS. 11 to 13 will be specifically described with reference to the drawings. In addition, about the component same as the secondary battery shown in FIG. 11 thru | or FIG. 13, the same code | symbol is attached | subjected and description is abbreviate | omitted.
[0015]
First embodiment In the secondary battery of the present embodiment, as shown in Fig. 1, a through hole (14) is formed in the lid (12) constituting the battery can (1), and the through hole is formed. The gas discharge valve (4) is fixed by welding by closing the hole (14). Further, a circumferential groove (5) is provided on the surface of the lid (12) so as to surround the gas discharge valve (4), and between the circumferential groove (5) and the gas discharge valve (4), An aperture portion (51) is formed.
[0016]
The gas discharge valve (4) is formed by fixing a disc-shaped valve membrane (42) to an annular ring body (41) as shown in FIG. On the other hand, the through hole (14) opened in the lid (12) is formed in a stepped groove into which the gas discharge valve (4) can be engaged.
The gas exhaust valve (4) is mounted on the through hole (14) of the lid (12) as shown in FIG. It is fixed by welding.
[0017]
At this time, an annular throttle part (51) is formed on the surface of the lid (12) so as to surround the welded part (15) of the gas discharge valve (4). First, it is transmitted to the throttle part (51), and then transmitted to the periphery of the throttle part (51) and diffused. Therefore, the throttle part (51) becomes a heat conduction resistance, and heat dissipation during welding is suppressed. As a result, the molten welded portion (15) is gradually cooled, and the gas discharge valve (4) is welded and fixed to the lid (12) without causing defects such as cracks and pinholes.
[0018]
In this embodiment, the lid (12) is made of aluminum, and as shown in FIG. 3, the outer diameter E is 60 mm, the thickness F is 4 mm, the thickness T is 1.0 mm, and the lid (12). The inner diameter H of the gas discharge valve (4) is 9 mm, the inner circumferential surface diameter A of the circumferential groove (5) is 11 mm, the outer circumferential diameter B is 13 mm, the circumferential groove (5) groove width C is set to 1 mm and the groove depth G is set to 1.5 mm.
[0019]
In order to demonstrate the effect of the secondary battery of the present invention, the battery can of the present invention provided with the throttle part (51) in the lid (12) and the battery can as a comparative example not provided with the throttle part (51) Each of the 10 lids was prepared, and a leak check with nitrogen gas and a check of the operating pressure of the gas discharge valve were performed. The results are shown in Table 1. In the leak check, pressurization was performed with nitrogen gas of 3 kg / cm ² , and the presence or absence of leak was examined with a soap solution. As the gas discharge valve, a valve with a working pressure specification of 8 ± 1 Kg / cm ² as a single valve was used.
[0020]
[Table 1]

[0021]
As is apparent from the results in Table 1, in the lid of the present invention, no leak was observed, and the operating pressure was within the specified value. On the other hand, in the comparative example, pinholes and cracks occurred in the four lid bodies, and a decrease in the operating pressure of the gas discharge valve was observed in the three lid bodies. As a cause of pinholes and cracks, it is conceivable that the temperature drop of the welded portion is abrupt because of the significant heat dissipation during laser welding. The cause of the decrease in the operating pressure is that the heat dissipation during laser welding is significant, so that the welding time becomes excessively long and the valve membrane (42) of the gas discharge valve (4) is overheated, It is conceivable that the valve membrane (42) was deformed by the stress and a thin portion was locally generated.
[0022]
In addition, immediately after the gas discharge valve (4) is laser welded to the lid of the present invention (FIG. 4 (a)) and the conventional lid (FIG. (B)) which does not include the throttle part (51) (5 After 20 seconds, the temperature of each part of the lid (12) was measured by thermography. The results are shown in Tables 2 and 3. In addition, measurement location No. in the table. Corresponds to the number positions shown in FIGS.
[0023]
[Table 2]

[Table 3]

[0024]
In the conventional lid, the heat dissipation during welding is remarkable, and the temperature drop after welding is abrupt. As a result, pinholes and cracks are generated in the welded portion as described above.
On the other hand, in the lid of the present invention, since the constricted portion of the heat flow path is formed, the temperature drop after welding is relatively small, thereby preventing pinholes and cracks as described above. The gas discharge valve can be welded without generating it.
[0025]
Further, in the secondary battery of the present invention, in order to investigate the optimum range of the groove width of the circumferential groove (5), the through-hole (14) having a diameter of 60 mm, a thickness of 4.1 mm, an inner diameter of 10 mm and a depth of 1. A lid body of the present invention in which a circumferential groove (5) of 5 mm is formed, wherein the circumferential groove (5) has various groove widths, and the temperature 5 seconds after the gas discharge valve is welded Measurement and a leak check with nitrogen gas of 3 kg / cm ² were performed.
Further, only the peripheral grooves (5) having the same dimensions as the respective lids are provided to make lids having no through holes (14), and leak check with nitrogen gas of 20 kg / cm ² is performed on these lids. And the presence or absence of the deformation | transformation and distortion of a cover body was confirmed with the level meter. The results are shown in Table 4.
[0026]
[Table 4]

[0027]
As is apparent from the results in Table 4, when the width of the circumferential groove (5) is smaller than 1/50 of the inner diameter of the through hole (14), the temperature drop near the welded portion is remarkable, thereby generating a pinhole. Is. Moreover, when the width of the circumferential groove (5) is larger than the inner diameter of the through hole (14), the strength of the lid (12) is extremely lowered and can withstand a predetermined pressure (20 Kg / cm ² ). Absent. Therefore, it can be said that the groove width of the circumferential groove (5) is preferably in the range of 1/50 to 1 of the inner diameter H of the through hole (14) of the lid (12).
[0028]
Further, in the secondary battery of the present invention, in order to investigate the optimum range of the depth of the circumferential groove (5), the circumferential groove (5) has a width of 1 mm and has various groove depths. A lid having the same dimensions as the above was produced, and the same pressure resistance test was performed. The results are shown in Table 5.
[0029]
[Table 5]

[0030]
As is apparent from the results in Table 5, when the depth of the circumferential groove (5) exceeds 2/3 of the thickness F of the lid (12), a problem occurs in the strength of the lid (12). Therefore, it can be said that the depth of the circumferential groove (5) is desirably 2/3 or less of the thickness F of the lid (12).
[0031]
Second embodiment As shown in Fig. 5, the secondary battery of this embodiment includes a cylindrical protrusion (6) surrounding the through hole (14) on the surface of the lid (12). The gas discharge valve (4) is welded and fixed to the central opening of the projection (6). In the secondary battery, the projecting portion (6) serves as the throttle portion (51) to suppress heat dissipation of the welded portion (15).
[0032]
Third embodiment As shown in Fig. 6, the secondary battery of the present embodiment is provided with the circumferential groove (5) of the first embodiment in the periphery of the convex portion (6) of the second embodiment. It is a thing.
[0033]
Fourth embodiment The secondary battery of the present embodiment has a concave groove (5) similar to that of the first embodiment on the back surface of the lid (12) as shown in FIG. is there. In the secondary battery, the throttle part (51) is formed between the bottom surface of the circumferential groove (5) and the surface of the lid (12).
[0034]
Fifth embodiment As shown in Fig. 8, the secondary battery of the present embodiment is not a continuous groove (5) as in the first embodiment, but is intermittent at one or more points. It is provided with a circumferential groove (5). In place of the plurality of circumferential grooves (5), a large number of circular holes may be arranged in the circle.
In any of the second to fifth embodiments, it goes without saying that the same effect as the secondary battery of the first embodiment can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part of a secondary battery according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing steps (a) and (b) for welding and fixing a gas discharge valve to a lid in the secondary battery.
FIG. 3 is a cross-sectional view showing dimensions of each part of the lid.
FIG. 4 is a view showing a temperature measurement place in the lid body of the present invention (a) and the lid body of the comparative example (b).
FIG. 5 is a cross-sectional view of a lid according to a second embodiment.
FIG. 6 is a cross-sectional view of a lid according to a third embodiment.
FIG. 7 is a cross-sectional view of a lid body according to a fourth embodiment.
FIG. 8 is a plan view of a plurality of circumferential grooves recessed in the lid of the fifth embodiment.
FIG. 9 is a cross-sectional view showing a main part of a secondary battery having a conventional pressure release type gas discharge valve.
FIG. 10 is a cross-sectional view showing steps (a) and (b) for welding and fixing a gas discharge valve to the lid in the secondary battery.
FIG. 11 is a perspective view of a cylindrical lithium secondary battery having a conventional pressure open / close type gas discharge valve.
FIG. 12 is an exploded perspective view of the secondary battery.
FIG. 13 is a cross-sectional view illustrating a main part of the secondary battery.
[Explanation of symbols]
(1) Battery can
(11) Tube
(12) Lid
(14) Through hole
(4) Gas discharge valve
(41) Ring body
(42) Valve membrane
(5) Circumferential groove
(51) Aperture
(6) Convex part

Claims

The lid (12) is fixed to the opening of the cylindrical body (11), and the battery can (1) is hermetically sealed. The secondary battery element is accommodated in the lid (12). the battery can (1) of the internal pressure is disc-shaped valve made from formed ring body on the outer peripheral portion (41) of the valve membrane (42) and the valve membrane (42) which opens when exceeding the predetermined value (4) However, in the secondary battery in which the outer peripheral portion of the ring body (41) is fixed by laser welding to the opening edge of the through hole (14) provided in the lid body (12), the lid body (12) The secondary battery is characterized in that a throttle part (51) is formed around the welded part of the valve (4) for reducing the cross-sectional area of the heat flow path through which heat during welding passes.

A circumferential groove (5) is formed in the front or back surface of the lid (12) so as to surround and extend the welded portion of the valve (4), and the valve side surface of the circumferential groove (5) and the valve ( The secondary battery according to claim 1, wherein the narrowed portion (51) is formed between the welded portion of 4).

The groove width of the circumferential groove (5) is in the range of 1/50 to 1 of the inner diameter of the through hole (14) provided in the lid (12), and the groove depth is 2 of the thickness of the lid (12). The secondary battery according to claim 2, which is / 3 or less.

The throttle part (51) is formed by a cylindrical convex part (6) projecting from the surface of the lid (12) so as to surround the through hole (14), and is formed in the central opening of the convex part (6). The secondary battery according to claim 1, wherein the valve (4) is fixed by welding.

The secondary battery according to any one of claims 1 to 4, wherein the battery capacity is 5 Ah or more and 200 Ah or less, and the thickness of the lid (12) is 1 to 5 mm.