JP2004342433A

JP2004342433A - Flat square battery

Info

Publication number: JP2004342433A
Application number: JP2003136856A
Authority: JP
Inventors: Masami Suzuki; 正美鈴木; Koji Kano; 幸司加納
Original assignee: Toshiba Battery Co Ltd
Current assignee: FDK Twicell Co Ltd
Priority date: 2003-05-15
Filing date: 2003-05-15
Publication date: 2004-12-02
Anticipated expiration: 2023-05-15
Also published as: JP4505711B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat square battery with an excellent sealing property of which the inner case is prevented from being slanted and bent inside when caulked, and the strength of a sealed part is improved. <P>SOLUTION: For the flat square battery with its thickness smaller than its external dimension having at least not less than two linear parts having ends connected by an almost circular arc-shaped curved part, in which an external case and an inner case made of metals are fitted into each other in a direction vertical to the flat surface of the battery through an insulation gasket, and the external case arranged at the outer peripheral side of the insulation gasket has a sealed structure caulked by caulking, a metal reinforcing member is inserted into the inner peripheral surface of the inner case, so that the deformation of the inner case generated at the peripheral linear part when caulking and sealing is prevented and a sealing property is improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、電池の封口性を向上する扁平角形電池に関する。
【０００２】
【従来の技術】
携帯電話やＰＤＡなどの小型情報端末を中心に使用機器の小型化が加速しており、主電源である二次電池についても小型化を図ることが要求されている。このような要求に応える電池として、例えば特許文献１や特許文献２に示すような負極端子を兼ねる金属製の負極ケースと、正極端子を兼ねる金属製の正極ケースが、絶縁ガスケットを介し嵌合され、さらに前記正極ケースまたは負極ケースが加締め加工により加締められた封口構造を有し、その内部に少なくとも正極、セパレータ、負極を含む発電要素と、非水電解質を内包した扁平形非水電解質二次電池において、扁平形電池の扁平面に垂直な方向の断面を見た場合に、少なくとも３面以上の正極と負極がセパレータを介し対向している正負極対向面を有した電極群が収納され、かつ、電極群内の正負極対向面積の総和が絶縁ガスケットの開口面積よりも大きくなるように構成された扁平形非水電解質二次電池が提案されている。
【０００３】
【特許文献１】
特願平１１−２４０９６４号
【特許文献２】
特願平１１−２４１２９０号
【０００４】
さらに最近になり、液晶をはじめとした表示装置を有する小型機器は、薄型化を進める一方、表示装置の小型化には実使用上限度があるため、機器全体に占める表示装置の占有面積比率を極力大きくして、機器全体を小型化することが検討されている。この表示装置の多くは角形状を有していることから、この形状に機器を合わせるため機器全体が角形状を有するものが多くなっており、機器内での電池の搭載には周縁部に少なくとも２つ以上の直線部を有し、各直線部の端部が略円弧状曲線部により結ばれている角型や小判型に代表される小型の扁平角形電池が望まれている。
【０００５】
しかしながら、従来のＬｉイオンやニッケル水素二次電池に見られるような深絞りをした外装ケースに封口板をレーザー溶接して封口している電池では、薄缶の製缶や電極挿入などの組立工程上の制約から電池の小型化に対してほぼ限界に来ている。
【０００６】
そこで、より小さく薄い略角形状を有する電池を製作するには新たな封口構造を用いた電池が必要であり、金属製の外装ケースと内装ケースが内部に電極を保持した状態で絶縁ガスケットを介し嵌合され、さらに外装ケースを加締め加工により封口部を形成した電池が望ましい。
【０００７】
この要求を満たす電池の例が特許文献３に開示されているが、実際にこのような電池を製作した場合、外装ケースの周縁直線部にスプリングバックが生じ封口が甘くなったり、外装ケースを加締める際に内装ケースの側壁が内側に内傾や湾曲を起こし、周縁直線部の封口が周縁曲線部の封口に対し劣り、十分な封口性を得ることはできなかった。内装ケース側壁の内傾や湾曲を防ぐ方法として特許文献４には内装ケースの側壁立ち上がり部に複数のＶノッチを設ける方法が、また、特許文献５には内装ケースの側壁の一部を肉厚にし改善を図る方法が提案されているが、従来の円型コイン電池に比べると依然として扁平角形電池の封口性は劣り、決して十分であるとは言えなかった。また、後者の場合、本発明者らが効果を確認するためにプレス加工による部品の製作を検討したところ、製作が困難であり、改善効果の確認ができなかった。切削加工等の他の方法により部品の製作が可能だとしても量産性に劣るものと考えられる。
【０００８】
【特許文献３】
特開２０００−１６４２５９号公報
【特許文献４】
特開２００２−１２４２１９号公報
【特許文献５】
特開２００２−１３４０７１号公報
【０００９】
【発明が解決しようとする課題】
本発明は上記情況に対処するためになされたもので、その課題は、加締め加工時の内装ケースの内傾及び湾曲を防止し、かつ、封口部の強度を高め、封口性の優れた扁平角形電池を提供することである。
【００１０】
【課題を解決するための手段】
本発明は金属製の外装ケースと金属製の内装ケースが、絶縁ガスケットを介し嵌合され、さらに外周側に配置された外装ケースが加締め加工により加締められた封口構造を有する扁平形電池であって、周縁部に少なくとも２つ以上の直線部（以後、周縁直線部Ｂとする）を有し、各直線部の端部が略円弧状曲線部（以後、周縁曲線部Ａとする）により結ばれている扁平角形電池において、内装ケースの内周面に金属製の補強材を挿入することを特徴とするものである。
【００１１】
このように内装ケースの内周面に金属製の補強材を挿入することで内装ケース側壁の強度を高め、内装ケース側壁の内傾及び湾曲を防止することで電池の封口性を向上させるものである。
【００１２】
図８に従来の電池を周縁直線部で切断した場合の封口部の断面拡大図を示す。
図に示すように、封口性を向上させるために外装ケースに施す加締め加工を強めた場合、外装ケース１の加締め加工に伴い、内装ケース４の側壁部に内傾が生じ、ガスケット６と内装ケース４の側壁部の間に隙間が生じてしまう。そのため、外装ケース先端と内装ケース先端がそれぞれガスケットに当る部位の、ガスケットの圧縮率を上げても電池の封口性は向上しない。
【００１３】
また、本発明者らは特許文献４に記載されているように、内装ケースの側壁の立ち上がり部に複数のＶノッチを設けた構造について検討を行ったが、内装ケースの内傾は止まらず、封口性の向上は見られなかった。
【００１４】
これに対し、本発明の電池では図３の断面拡大図に示すように、補強材７により内装ケース側壁の強度が著しく向上するため、加締め加工を行っても内装ケース４の内傾が生じず、ガスケット６と内装ケース側壁の隙間が生じることがなく封口性に優れた電池が得られることが分かった。
【００１５】
補強材７の材質については強度を得ることが目的であるため、金属製であることが望ましく、金属の種類は電池の内容物に合わせ腐食やガス発生の防止を加味し適宜選定することができる。リチウムイオン二次電池やリチウム電池であれば、鉄やステンレス材を用いるのが良く、水溶液を電解液に用いた電池では真鍮やこれらの金属に銅やスズ、亜鉛めっきを施したものでも良い。また、チタンやその合金も使用することができる。また、これらの金属に樹脂等をコーティングしたものを用いても良い。その場合、基体の金属としてアルミ合金やマグネシウム合金も使用可能である。
【００１６】
補強材の形状については電池容量を決定する電極面積に影響を与えない形状が好ましく、内装ケース側壁に設けた段部の水平面と段部より先の側壁部とガスケット底面のなす空間に収まる形状にし、配置するのが良い。
【００１７】
さらに、経済性と生産性を考慮すると板材のプレス加工により製作できることが好ましく、図３に示した如く断面形状が長方形（または正方形）とするのが打抜き加工で製造できるので好ましい。なお、図３の場合、外周部をトリミングする際に断面長方形の一角をＲ形状にプレスし内装ケースの形状に合わせている。
【００１８】
他の形状としては図４に示す如く薄板をＬ字形に加工するのが良い。これも断面Ｚ字形にプレスした後、外周部をトリミングすることで製作でき、順送り型が使えるので安価に製作できる。また、断面長方形の場合に比べ薄くできる分、打抜きロスが減り好ましい。また、同じ板厚ならこちらの方が補強材としての強度が高い。
【００１９】
さらに図５及び図６に示した断面レ字形やＵ字形の形状としても良い。これらも順送り型により製作できるので、先の断面Ｌ字形に比べさらに補強材としての強度が高められる。
【００２０】
また、図７に示した如く断面Ｌ字形の補強材を図４の場合と上下逆で設置することもできる。この場合、補強材の外周トリミング部の先端Ｒ形状を逆向きにプレスし直し、内装ケース内面のＲ形状に合わせるようにするのが良い。
【００２１】
ここで、本発明は扁平角形電池の封口構造について、詳しくは補強材により内装ケースの強度を向上させ、電池の封口性を向上することに主点を置いたものであり、電池構造および電極構成については限定されるものではなく、電極構造については、薄膜電極を捲回した捲回電極の他、薄膜電極を積層した積層電極、顆粒を成形したペレット電極、金属ネットに活物質を充填した充填電極等、あらゆる電極について適用することができ、本発明と同様の効果が期待できる。
【００２２】
【発明の実施の形態】
以下、本発明の実施例及び比較例について、リチウムイオン二次電池を例に、詳細に説明する。
【００２３】
（実施例１）
図１は本実施例１の電池の断面図、図２はその平面図、図３は電池の周縁直線部で切断した場合の封口部の断面拡大図である。
次に、本実施例１の電池の製造方法を説明する。
【００２４】
まず、ＬｉＣｏＯ_２１００質量部に対し、導電材としてアセチレンブラック５質量部と黒鉛粉末５質量部を加え、結着剤としてポリフッ化ビニリデンを５質量部加え、Ｎ−メチルピロリドンで希釈、混合し、スラリー状の正極合剤を得た。
次にこの正極合剤を、正極集電体である厚さ０．０２ｍｍのアルミ箔の片面にドクターブレード法により塗工、乾燥を行い、アルミ箔表面に正極作用物質含有層を形成した。以後、正極作用物質含有層の塗膜厚さが両面で０．１５ｍｍとなるまで塗工、乾燥を繰り返し、両面塗工正極を作製した。次に、この電極体の片面の端から２０ｍｍ部分の作用物質含有層を除去し、アルミ層を剥き出し通電部とし、幅１９ｍｍ、長さ２００ｍｍ、厚さ０．１５ｍｍの長さに切り出した正極板を作製した。
【００２５】
次に、黒鉛化メソフェーズピッチ炭素繊維粉末１００質量部に結着剤としてスチレンブタジエンゴム（ＳＢＲ）とカルボキシメチルセルロース（ＣＭＣ）をそれぞれ２．５質量部を添加し、イオン交換水で希釈、混合し、スラリー状の負極合剤を得た。得られた負極合剤を負極集電体である厚さ０．０２ｍｍの銅箔に作用物質含有層の厚さが０．１５ｍｍとなるように正極の場合と同様に塗工、乾燥を繰り返し実施し、両面塗工負極を作製した。次に、この電極体の片面の端から２０ｍｍ部分の作用物質含有層を除去し、銅層を剥き出し通電部とし、幅２０ｍｍ、長さ２００ｍｍ、厚さ０．１５ｍｍの長さに切り出した負極板を作製した。
次に、正負極通電部面を外周巻き終わり側とし、これら正極と負極の間に幅２２ｍｍ、厚さ２５μｍのポリエチレン微多孔膜からなるセパレータを介し渦巻状に捲回し、扁平形電池の扁平面に対し水平方向に正負極対向部を持つように一定方向に捲回電極の中心部の空間がなくなるまで加圧した。以上の方法により縦２２ｍｍ、横２２ｍｍの扁平コイル状の電極群３を製作した。
【００２６】
次に板厚０．２５ｍｍのステンレス材からなる内装ケース（負極金属ケース）４の内面に厚さ０．０３ｍｍのステンレス製の金属ネット５を溶接し、ステンレス材からなる断面が全周にわたり略長方形の補強材７を内装ケース４の内面に圧入した後、シール剤としてアスファルトピッチを全面に塗布した絶縁ガスケット６と一体化した。絶縁ガスケットの底部肉厚は０．６５ｍｍである。
【００２７】
ここで用いた補強材は厚さ０．７ｍｍの板材を角リング状に打抜き加工を行ったものであり、一辺の断面形状は周縁曲線部の断面形状を含め、全周にわたり厚さ０．７ｍｍ、幅０．８ｍｍの略長方形であり、内装ケースの曲げＲ部と接する一角は打抜き加工の際にＲ０．２５ｍｍに成形したものである。続いて８５℃で１２ｈ乾燥処理を行った電極群３を電極群の片面塗工負極板の未塗工側が前述の金属ネット５に接するように配置し、エチレンカーボネートとメチルエチルカーボネートを体積比１：１の割合で混合した溶媒に支持塩としてＬｉＰＦ_６を１ｍｏｌ／ｌの割合で溶解せしめた非水電解質を注液し、さらに電極群の片面塗工正極板の未塗工側に接するように厚さ０．０３ｍｍのＡｌ製の金属ネット２が内面に溶接された、板厚０．２ｍｍのステンレス材の内面に厚さ５０μｍのＡｌがクラッド処理された板厚０．２５ｍｍのクラッド材からなる外装ケース（正極ケース）１を嵌合し、上下反転後、外装ケースに加締め加工を実施し、封口し、厚さ３．２ｍｍ、縦３０ｍｍ、横３０ｍｍの実施例１の扁平角形非水電解質二次電池を製作した。
【００２８】
（実施例２）
補強材７の断面形状が図４に示す如く、水平長０．８ｍｍ、高さ０．９ｍｍ、厚さ０．３ｍｍ、折り曲げ部のＲが外ＲでＲ０．３ｍｍのＬ字形状である以外は実施例１と同様に電池を製作した。
【００２９】
（実施例３）
補強材７の断面形状が図５に示す如く、長さ０．８ｍｍ、高さ０．９ｍｍ、厚さ０．３ｍｍのレ字形状である以外は実施例１と同様に電池を製作した。
【００３０】
（実施例４）
補強材７の断面形状が図６に示す如く、内辺高さ０．８ｍｍ、外辺高さ０．９ｍｍ、厚さ０．３ｍｍのＵ字形状である以外は実施例１と同様に電池を製作した。
【００３１】
（実施例５）
実施例２に用いた補強材７を先端部が逆ＲでＲ０．２５ｍｍとなるように上下から圧縮し水平長０．８ｍｍ、高さ０．７ｍｍ、厚さ０．３ｍｍのＬ字形状の補強材を製作した。この補強材を実施例２の場合とは上下逆さに圧入し、それ以外は実施例１と同様に図７に示した断面形状の電池を製作した。
【００３２】
（比較例１）
補強材を用いず、ガスケットに内突起がついた形状のものを用いた以外は、実施例１と同様に電池を製作し、図８に示した断面形状を持つ電池を得た。
【００３３】
（比較例２）
図９に示した如く内装ケース４の側壁立ちあがり部に一辺に対し３箇所のＶノッチ４ａをつけた以外は、比較例１と同様に電池を製作した。
【００３４】
以上のとおり、本実施例１〜５、比較例１、２の電池を各１００個製作した。その後、４．２Ｖ、１０ｍＡの定電流定電圧で４８ｈ初充電を実施し、３日間室温で放置後、６０℃−９３％ＲＨの雰囲気下で６０日間保存し、電池の漏液の有無を目視にて確認した。結果を表１に示す。
【００３５】
【表１】

【００３６】
表１より明らかであるが、補強材を挿入した本発明の実施例１〜５の電池は、補強材を挿入していない比較例１の電池に比べ封口性が優れており、また、内装ケースにＶノッチを設けた比較例２の電池に対しても封口性の向上が認められる。
【００３７】
なお、本発明の実施例は、非水電解質に非水溶媒を用いた扁平形非水溶媒二次電池を用いて、正極ケースを外装ケースとした場合の加締め加工により封口する扁平角形電池について説明したが、正負極電極を入れ替え、外装ケースとして負極ケースを配置することも可能である。さらに、他の電池系への適用も可能であり、扁平角形の加締め封口については本発明と同様の効果が得られる。
【００３８】
【発明の効果】
以上説明したとおり、本発明によれば加締め封口時の周縁直線部に生じる内装ケースの変形を防止し、封口性を向上させることで、工業的価値の非常に大きい扁平角形電池を提供することができる。
【図面の簡単な説明】
【図１】図１の電池の断面図。
【図２】図１の電池の平面図。
【図３】実施例１の電池の周縁直線部の封口部断面拡大図。
【図４】実施例２の電池の周縁直線部の封口部断面拡大図。
【図５】実施例３の電池の周縁直線部の封口部断面拡大図。
【図６】実施例４の電池の周縁直線部の封口部断面拡大図。
【図７】実施例５の電池の周縁直線部の封口部断面拡大図。
【図８】比較例１の電池の周縁直線部の封口部断面拡大図。
【図９】比較例２の電池に用いた内装ケースの上面図。
【符号の説明】
１…外装ケース（正極ケース）、２…正極集電体、３…扁平渦巻状電極群、４…内装ケース（負極ケース）、４ａ…Ｖノッチ、５…負極集電体、６…絶縁ガスケット、７…補強材、Ａ…周縁曲線部、Ｂ…周縁直線部。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a flat rectangular battery that improves the sealing performance of the battery.
[0002]
[Prior art]
The miniaturization of devices used, especially small information terminals such as mobile phones and PDAs, is accelerating, and miniaturization of secondary batteries, which are main power sources, is also required. As a battery meeting such a requirement, for example, a metal negative electrode case also serving as a negative electrode terminal and a metal positive electrode case also serving as a positive electrode terminal as shown in

Patent Documents

1 and 2 are fitted via an insulating gasket. Further, a power generating element including at least a positive electrode, a separator, and a negative electrode therein, and a flat nonaqueous electrolyte containing a nonaqueous electrolyte therein, further comprising a sealing structure in which the positive electrode case or the negative electrode case is tightened by caulking. In the secondary battery, an electrode group having a positive / negative electrode facing surface where at least three or more positive electrodes and negative electrodes face each other with a separator interposed therebetween when a cross section in a direction perpendicular to the flat surface of the flat battery is viewed. A flat non-aqueous electrolyte secondary battery has been proposed in which the total area of the positive and negative electrodes facing each other in the electrode group is larger than the opening area of the insulating gasket.
[0003]
[Patent Document 1]
Japanese Patent Application No. 11-240964 [Patent Document 2]
Japanese Patent Application No. 11-241290 [0004]
More recently, small devices having a display device such as a liquid crystal device have been reduced in thickness, but the miniaturization of the display device has an upper limit of actual use. It is being studied to reduce the size of the entire device by making it as large as possible. Since many of these display devices have a rectangular shape, many devices have a square shape in order to fit the device to this shape, and at least a peripheral portion is required for mounting a battery in the device. There is a demand for a small flat prismatic battery represented by a square or oval type having two or more straight portions and ends of the straight portions connected by a substantially arc-shaped curved portion.
[0005]
However, in the case of a battery in which a sealing plate is sealed by laser welding to a deep drawn outer case as seen in conventional Li-ion or nickel-metal hydride secondary batteries, the assembly process such as making thin cans and inserting electrodes Due to the above restrictions, the miniaturization of batteries has almost reached its limit.
[0006]
Therefore, in order to manufacture a smaller and thinner battery having a substantially rectangular shape, a battery using a new sealing structure is necessary.A metal outer case and an inner case hold an electrode inside through an insulating gasket. It is desirable that the battery be fitted and further formed with a sealing portion by caulking the outer case.
[0007]
Patent Literature 3 discloses an example of a battery that satisfies this requirement. However, when such a battery is actually manufactured, springback occurs on the peripheral straight portion of the outer case, resulting in a weaker seal or an additional outer case. When tightening, the side wall of the interior case was inclined inward and curved inward, and the sealing at the peripheral straight portion was inferior to the sealing at the peripheral curved portion, so that sufficient sealing performance could not be obtained. Patent Literature 4 discloses a method of providing a plurality of V notches at the rising portion of the side wall of the interior case, and Patent Literature 5 discloses a method of preventing a part of the side wall of the interior case from being thickened. Although there has been proposed a method of improving the shape, the flat rectangular battery still has a poor sealing property as compared with the conventional circular coin battery, and it cannot be said that it is sufficient. In the latter case, when the present inventors examined the production of parts by press working in order to confirm the effect, the production was difficult and the improvement effect could not be confirmed. It is considered that mass production is inferior even if parts can be manufactured by other methods such as cutting.
[0008]
[Patent Document 3]
Japanese Patent Application Laid-Open No. 2000-164259 [Patent Document 4]
Japanese Patent Application Laid-Open No. 2002-124219 [Patent Document 5]
JP-A-2002-134071
[Problems to be solved by the invention]
The present invention has been made in order to address the above situation, and has as its object to prevent the inner case from inclining and curving during crimping, and to increase the strength of the sealing portion, and to provide a flat shape excellent in sealing performance. It is to provide a prismatic battery.
[0010]
[Means for Solving the Problems]
The present invention relates to a flat battery having a sealed structure in which a metal outer case and a metal inner case are fitted via an insulating gasket, and an outer case arranged on the outer peripheral side is further tightened by swaging. The peripheral portion has at least two or more linear portions (hereinafter referred to as peripheral linear portions B), and the end of each linear portion is formed by a substantially arc-shaped curved portion (hereinafter referred to as peripheral curved portion A). In the tied flat prismatic battery, a metal reinforcing material is inserted into the inner peripheral surface of the interior case.
[0011]
By inserting a metal reinforcing material into the inner peripheral surface of the inner case in this way, the strength of the inner case side wall is increased, and the inward inclination and bending of the inner case side wall are prevented to improve the sealing property of the battery. is there.
[0012]
FIG. 8 shows an enlarged cross-sectional view of a sealing portion when a conventional battery is cut along a peripheral straight portion.
As shown in the figure, in the case where the caulking process performed on the outer case is strengthened to improve the sealing property, the inner case 4 is inclined inward with the caulking process of the outer case 1 and the gasket 6 A gap is created between the side walls of the interior case 4. Therefore, even if the compression ratio of the gasket is increased at the portions where the outer case tip and the inner case tip respectively contact the gasket, the sealing performance of the battery is not improved.
[0013]
Further, as described in Patent Document 4, the present inventors have studied a structure in which a plurality of V notches are provided at a rising portion of a side wall of an interior case. However, the inner case of the interior case does not stop. No improvement in the sealing property was observed.
[0014]
On the other hand, in the battery of the present invention, as shown in the enlarged cross-sectional view of FIG. 3, since the strength of the inner case side wall is significantly improved by the reinforcing member 7, the inner case 4 inclines even when crimping is performed. Thus, it was found that there was no gap between the gasket 6 and the side wall of the interior case, and a battery having excellent sealing properties was obtained.
[0015]
The material of the reinforcing member 7 is desirably made of metal because the purpose is to obtain strength, and the type of metal can be appropriately selected in consideration of corrosion and gas generation in accordance with the contents of the battery. . For a lithium ion secondary battery or a lithium battery, iron or stainless steel is preferably used. For a battery using an aqueous solution as an electrolyte, brass or a metal obtained by plating copper, tin, or zinc on these metals may be used. Titanium and its alloys can also be used. Further, a material obtained by coating a resin or the like on these metals may be used. In that case, an aluminum alloy or a magnesium alloy can be used as the metal of the base.
[0016]
Regarding the shape of the reinforcing material, a shape that does not affect the electrode area that determines the battery capacity is preferable, and a shape that fits in the space formed by the horizontal surface of the step provided on the inner case side wall, the side wall ahead of the step, and the gasket bottom surface is preferable. It is good to arrange.
[0017]
Further, in consideration of economy and productivity, it is preferable to be able to manufacture by pressing a plate material, and it is preferable that the cross-sectional shape is rectangular (or square) as shown in FIG. In the case of FIG. 3, when trimming the outer peripheral portion, one corner of a rectangular cross section is pressed into an R shape to match the shape of the interior case.
[0018]
As another shape, it is preferable to process a thin plate into an L shape as shown in FIG. This can also be manufactured by pressing the Z-shaped cross section and then trimming the outer peripheral portion. Since a progressive die can be used, it can be manufactured at low cost. In addition, punching loss is reduced because the thickness can be reduced as compared with a rectangular cross section, which is preferable. Also, if the thickness is the same, this one has higher strength as a reinforcing material.
[0019]
Further, the cross section may be shaped like a letter L or a letter U as shown in FIGS. Since these can also be manufactured by the progressive feeding type, the strength as a reinforcing material is further enhanced as compared with the above-mentioned L-shaped cross section.
[0020]
Further, as shown in FIG. 7, a reinforcing member having an L-shaped cross section can be installed upside down as in FIG. In this case, it is preferable to press the tip R shape of the outer peripheral trimming portion of the reinforcing material in the opposite direction again so as to match the R shape of the inner surface of the interior case.
[0021]
Here, the present invention relates to a sealing structure of a flat prismatic battery, and more particularly, to enhance the strength of an interior case with a reinforcing material and to improve the sealing performance of a battery. The electrode structure is not limited, and the electrode structure may be a wound electrode obtained by winding a thin film electrode, a laminated electrode obtained by laminating thin film electrodes, a pellet electrode formed by molding granules, or a metal net filled with an active material. The present invention can be applied to any electrode such as an electrode, and the same effect as the present invention can be expected.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, Examples and Comparative Examples of the present invention will be described in detail using a lithium ion secondary battery as an example.
[0023]
(Example 1)
FIG. 1 is a cross-sectional view of the battery of the first embodiment, FIG. 2 is a plan view thereof, and FIG. 3 is an enlarged cross-sectional view of a sealing portion cut along a peripheral straight portion of the battery.
Next, a method for manufacturing the battery of the first embodiment will be described.
[0024]
First, for 100 parts by mass of LiCoO ₂ , 5 parts by mass of acetylene black and 5 parts by mass of graphite powder are added as conductive materials, 5 parts by mass of polyvinylidene fluoride is added as a binder, and the mixture is diluted and mixed with N-methylpyrrolidone. A slurry-like positive electrode mixture was obtained.
Next, this positive electrode mixture was applied to one surface of a 0.02 mm thick aluminum foil as a positive electrode current collector by a doctor blade method, and dried to form a positive electrode active substance-containing layer on the surface of the aluminum foil. Thereafter, coating and drying were repeated until the coating thickness of the positive electrode active substance-containing layer reached 0.15 mm on both sides, to produce a double-side coated positive electrode. Next, the positive electrode plate cut out to a length of 19 mm, a length of 200 mm, and a thickness of 0.15 mm was removed by removing the active material-containing layer of 20 mm from the end of one side of the electrode body and exposing the aluminum layer as a current-carrying part. Was prepared.
[0025]
Next, 2.5 parts by mass of styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC) were added as binders to 100 parts by mass of the graphitized mesophase pitch carbon fiber powder, and the mixture was diluted and mixed with ion-exchanged water. A slurry-like negative electrode mixture was obtained. The obtained negative electrode mixture was repeatedly applied and dried on a 0.02 mm-thick copper foil as a negative electrode current collector in the same manner as in the case of the positive electrode so that the thickness of the active substance-containing layer was 0.15 mm. Then, a double-sided coated negative electrode was produced. Next, the negative electrode plate cut out to a length of 20 mm, a length of 200 mm, and a thickness of 0.15 mm by removing a 20 mm portion of the active substance-containing layer from one end of the electrode body and exposing the copper layer as an energized portion. Was prepared.
Next, the surface of the current-carrying portion of the positive and negative electrodes was set to the outer peripheral winding end side, and spirally wound between the positive electrode and the negative electrode through a separator made of a microporous polyethylene film having a width of 22 mm and a thickness of 25 μm. Then, pressure was applied until the space at the center of the wound electrode disappeared in a certain direction so as to have the positive and negative electrode facing portions in the horizontal direction. By the above method, a flat coil-shaped electrode group 3 having a length of 22 mm and a width of 22 mm was manufactured.
[0026]
Next, a metal net 5 made of stainless steel having a thickness of 0.03 mm is welded to the inner surface of an interior case (negative metal case) 4 made of stainless steel having a plate thickness of 0.25 mm, and the cross section made of the stainless material is substantially rectangular over the entire circumference. After press-fitting the reinforcing member 7 into the inner surface of the interior case 4, the insulating material 7 was integrated with the insulating gasket 6 coated with asphalt pitch as a sealant over the entire surface. The bottom thickness of the insulating gasket is 0.65 mm.
[0027]
The reinforcing material used here is obtained by punching a 0.7 mm-thick plate material into a square ring shape, and the cross-sectional shape of one side is 0.7 mm thick over the entire circumference, including the cross-sectional shape of the peripheral curved portion. , A rectangular shape having a width of 0.8 mm, and a corner in contact with the bent portion R of the interior case is formed to have an R of 0.25 mm at the time of punching. Subsequently, the electrode group 3 subjected to the drying treatment at 85 ° C. for 12 hours was arranged so that the uncoated side of the single-sided coated negative electrode plate of the electrode group was in contact with the metal net 5, and ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1 to 1. : A non-aqueous electrolyte in which LiPF ₆ was dissolved at a ratio of 1 mol / l as a supporting salt in a solvent mixed at a ratio of 1: 1 was injected, and the electrode group was brought into contact with the uncoated side of a single-side coated positive electrode plate. A metal net 2 made of Al having a thickness of 0.03 mm is welded to the inner surface, and a 0.25 mm thick clad material is formed by cladding a 50 μm thick Al on the inner surface of a 0.2 mm thick stainless steel material. After the outer case (positive case) 1 is fitted and turned upside down, the outer case is crimped, sealed, and has a flat rectangular nonaqueous electrolyte of Example 1 having a thickness of 3.2 mm, a length of 30 mm, and a width of 30 mm. Made rechargeable battery It was.
[0028]
(Example 2)
As shown in FIG. 4, except that the cross-sectional shape of the reinforcing member 7 is a horizontal length of 0.8 mm, a height of 0.9 mm, a thickness of 0.3 mm, and the bent portion R has an outer R and an R shape of R 0.3 mm. A battery was manufactured in the same manner as in Example 1.
[0029]
(Example 3)
A battery was manufactured in the same manner as in Example 1, except that the cross-sectional shape of the reinforcing member 7 was a rectangular shape having a length of 0.8 mm, a height of 0.9 mm, and a thickness of 0.3 mm as shown in FIG.
[0030]
(Example 4)
6, except that the cross-sectional shape of the reinforcing member 7 was a U-shape having an inner side height of 0.8 mm, an outer side height of 0.9 mm, and a thickness of 0.3 mm as shown in FIG. Made.
[0031]
(Example 5)
The reinforcing member 7 used in Example 2 was compressed from above and below so that the tip portion had a reverse R of R 0.25 mm and was L-shaped with a horizontal length of 0.8 mm, a height of 0.7 mm, and a thickness of 0.3 mm. Materials were made. This reinforcing material was press-fitted upside down as in Example 2, and a battery having the cross-sectional shape shown in FIG.
[0032]
(Comparative Example 1)
A battery was manufactured in the same manner as in Example 1 except that a reinforcing material was not used and a gasket having a shape with an inner protrusion was used, and a battery having a cross-sectional shape shown in FIG. 8 was obtained.
[0033]
(Comparative Example 2)
As shown in FIG. 9, a battery was manufactured in the same manner as in Comparative Example 1, except that three V-notches 4a were provided on one side of the side wall rising portion of the interior case 4.
[0034]
As described above, 100 batteries of Examples 1 to 5 and Comparative Examples 1 and 2 were manufactured. After that, the battery was initially charged at a constant current and a constant voltage of 4.2 V and 10 mA for 48 hours, left at room temperature for 3 days, stored in an atmosphere of 60 ° C. and 93% RH for 60 days, and visually inspected for leakage of the battery. Confirmed. Table 1 shows the results.
[0035]
[Table 1]

[0036]
As is clear from Table 1, the batteries of Examples 1 to 5 of the present invention in which a reinforcing material was inserted had better sealing properties than the battery of Comparative Example 1 in which no reinforcing material was inserted, and the interior case Also, the battery of Comparative Example 2 provided with a V notch also has improved sealing performance.
[0037]
Incidentally, the embodiment of the present invention, using a flat non-aqueous solvent secondary battery using a non-aqueous solvent for the non-aqueous electrolyte, for a flat prismatic battery that is sealed by caulking when the positive electrode case is an outer case As described above, it is also possible to replace the positive and negative electrodes and arrange a negative electrode case as an outer case. Furthermore, application to other battery systems is also possible, and the same effects as those of the present invention can be obtained for a flat rectangular caulked seal.
[0038]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a flat prismatic battery having an extremely large industrial value by preventing deformation of an interior case generated in a peripheral straight portion at the time of swaging and sealing and improving sealing performance. Can be.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of the battery of FIG.
FIG. 2 is a plan view of the battery of FIG.
FIG. 3 is an enlarged cross-sectional view of a sealing portion of a peripheral straight portion of the battery according to the first embodiment.
FIG. 4 is an enlarged cross-sectional view of a sealing portion of a peripheral straight portion of the battery of Example 2.
FIG. 5 is an enlarged cross-sectional view of a sealing portion of a peripheral linear portion of the battery according to the third embodiment.
FIG. 6 is an enlarged cross-sectional view of a sealing portion of a peripheral linear portion of a battery according to a fourth embodiment.
FIG. 7 is an enlarged cross-sectional view of a sealing portion of a peripheral straight portion of the battery of Example 5.
FIG. 8 is an enlarged cross-sectional view of a sealing portion of a peripheral straight portion of the battery of Comparative Example 1.
FIG. 9 is a top view of an interior case used for the battery of Comparative Example 2.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Outer case (positive case), 2 ... Positive electrode collector, 3 ... Flat spiral electrode group, 4 ... Inner case (negative electrode case), 4a ... V notch, 5 ... Negative electrode collector, 6 ... Insulating gasket, 7: Reinforcement, A: Peripheral curved portion, B: Peripheral straight portion.

Claims

The metal outer case and the metal inner case are fitted vertically to the flat surface of the battery via an insulating gasket, and the outer case disposed on the outer peripheral side of the insulating gasket is caulked by caulking. In a flat rectangular battery having a closed sealing structure, at least two or more straight portions at the peripheral edge and ends of each straight portion connected by a substantially arc-shaped curved portion, and the thickness of the battery is smaller than the outer dimensions. A flat battery having a metal reinforcing member inserted into an inner peripheral surface of the interior case.