JP4060576B2

JP4060576B2 - Flat battery

Info

Publication number: JP4060576B2
Application number: JP2001355143A
Authority: JP
Inventors: 徹也林; 眞中西; 聡小川; 晶夫袴田
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2001-11-20
Filing date: 2001-11-20
Publication date: 2008-03-12
Anticipated expiration: 2021-11-20
Also published as: JP2003157902A

Description

【０００１】
【発明の属する技術分野】
本発明は、コイン形電池及びその製造方法に関し、特に、正極板と負極板とをセパレータを介して巻回した巻回構造の極板群を用いて放電電流の増加を図ったコイン形電池に関するものである。
【０００２】
【従来の技術】
コイン形電池は、図９に示すように、円盤状に形成された正極ペレット３２と負極ペレット３３とをセパレータ３４を介して対向配置した極板構造のものが一般的に採用されている。このコイン形電池は円形半殻体に形成された封口ケース３５内に正極ペレット３２と負極ペレット３３とをセパレータ３４を介して対向配置し、電解液を注入し、封口ケース３５の側周部にガスケット３６を配設し、この上にキャップケース３１を被せ、キャップケース３１の開口端を内側に折り曲げるカシメ加工により内部空間を密閉し、コイン形の外観を呈する電池に形成される。
【０００３】
上記のような正極ペレット３２と負極ペレット３３とを１：１で対面させた極板構造では、正極板と負極板とが対極する反応面積が小さいことなどの要因によって大きな放電容量を得ることはできなかった。大きな放電容量を得るには正極板と負極板との対向面積を増加させる必要があり、コイン形電池以外の比較的大型の電池では複数枚の正極板と負極板とをセパレータを介して積層した積層構造や、帯状の正極板と負極板とをセパレータを介して巻回した巻回構造により、反応面積を拡大させて高率放電におけるエネルギー密度の向上を図った構造が広く用いられている。このような積層構造や巻回構造の極板を、コイン形の扁平なケース内に収容することができればコイン形電池の放電容量を増大化させることができる。コイン形のような扁平なケースに巻回構造の極板群を収容した電池は、本願出願人が特願２０００−２４１６７８号、特願２０００−２４１６７９号他として提案している。
【０００４】
この巻回構造の極板群は、図７に示すように、円形のケースにそれを収容するために、複数の正極積層面１７ａ〜１７ｅを連結片１９ａ〜１９ｄで連結した正極板７と、正極積層面１７ａ〜１７ｅより大きな面積に形成された複数の負極積層面１８ａ〜１８ｆを連結片２０ａ〜２０ｅで連結した負極板８とを、図８に模式的に示すように、セパレータ９を介して扁平に巻回して極板群１に形成している。この極板群１を用いることにより、小型扁平でありながら大きな放電電流を取り出すことができる電池として携帯電子機器等の小型化、高機能化に寄与できるものとなる。
【０００５】
【発明が解決しようとする課題】
しかしながら、正極板７と負極板８とを扁平に巻回すると、最も巻き始め側の折り曲げ位置となる正極板７の連結片１９ａ、負極板８の連結片２０ａでは小さい折り曲げ半径で１８０度に折り曲げられるため、極板の芯材である集電体に折損が生じる場合がある。特に、正極板７では集電体としてアルミニウム箔が用いられており、破断強度が低いため折損が生じやすくなる。
【０００６】
正極板７は、正極集電体の両面に正極活物質層が塗着されたものであり、これが連結片１９ａで小さい折り曲げ半径で１８０度に折り曲げられると、内側の正極活物質層は圧縮され、外側の正極活物質層は引き伸ばされるため、正極集電体にも引き伸ばす方向に力が作用して、破断強度が低いアルミニウム箔の正極集電体は破断する恐れがあった。
【０００７】
また、扁平形電池をリチウムイオン二次電池として構成した場合に、正極活物質としてコバルト酸リチウム等の遷移金属酸化物が、負極活物質としてリチウムイオンの吸蔵、放出が可能な黒鉛等の炭素材料が用いられる。このような正極活物質及び負極活物質を用いた二次電池では、充電時における黒鉛系材料の電位はリチウム析出が生じる電位とほぼ変わらないような低電位で使用されている。このため充放電サイクルの繰り返し等により負極活物質に劣化が生じた二次電池では、充電時に負極活物質に挿入されるリチウムイオンが電解液と不活性化反応を起こし、負極板８の表面にデンドライト状のリチウム金属が析出する現象が生じ、これに起因する内部短絡により二次電池の安全性及び寿命低下をまねくことが知られている。正極板と負極板とを円筒状に巻回した円筒形電池の場合に比して、本願発明の扁平形電池のように扁平に巻回して極板群を構成した場合に、上記リチウムデンドライトが充放電サイクルが少ない状態で発生することを発見された。
【０００８】
極板群が円筒状に巻回されている場合でも、扁平に巻回されている場合でも対向する極板の面積がほぼ等しい状態にあり、正極−負極間の容量はほぼ同一に保たれている。しかし、極板群を扁平に形成した場合には、負極板８の巻き始め側の端部は正極板７の巻き始め側の連結片１９ａに包み込まれるように対峙しており、前記端部に限定すると正極−負極間の容量バランスは正極側に大きく傾いている。このため、充電時に正極から離脱したリチウムイオンは負極の炭素材料の層間に吸蔵しきれず、過剰なリチウムイオンが負極表面上に析出するとの知見を得た。
【０００９】
本発明は扁平に巻回して極板群を構成した場合に生じる上記課題に鑑みて創案されたもので、巻回時の集電体に生じる破断及びリチウムデンドライトの発生を防止する構造を備えた扁平形電池を提供することを目的とする。
【００１０】
【課題を解決するための手段】
上記目的を達成するための本願第１発明は、正極集電体の両面に正極活物質層が形成された正極板材料を用いて複数の正極積層面を連結片で連結して帯状に形成した正極板と、負極集電体の両面に負極活物質層が形成された負極板材料を用いて複数の負極積層面を連結片で連結して帯状に形成した負極板とを、前記正極積層面と前記負極積層面とがセパレータを介して交互に積層されるように前記連結片で折り曲げて扁平に巻回した極板群が、封口ケースにガスケットを介してキャップケースを被せて形成される内部空間に収容されてなる扁平形電池において、前記負極板の巻き始め側端部が最内周部分に配置され、該負極板の巻き始め側端部を包み込むように前記正極板の最も巻き始め側に位置する連結片が配置されて、前記負極板と前記正極板とが巻回されてなり、前記負極板の巻き始め側端部を包み込む前記正極板の最も巻き始め側に位置する連結片の内面側に前記連結片の幅より広い絶縁性の樹脂テープが貼着されてなることを特徴とするものである。
【００１１】
上記第１発明によれば、正極板と負極板とをセパレータを介して扁平に巻回すると、最も巻き始め側に位置する連結片は小さい折り曲げ半径で折り曲げられることになり、極板の芯材である集電体、特に正極板では集電体にアルミニウム箔を用いた場合に、折り曲げによる引っ張りにより集電体が折損する恐れがあるが、連結片を折り曲げる内面側に樹脂テープが貼着されているので、樹脂テープの厚さ分だけ折り曲げ半径が大きくなり、鋭角に折り曲げられることがなくなるので、正極板の集電体としてアルミニウム箔を用いた場合にも折り曲げによる集電体の折損が防止できる。また、正極板の巻き始め側の連結片は負極板の巻き始め端部を包み込むように配置されるので、端部に限定すれば、この端部は集電体の切断加工によって切断面が露出しているので正極−負極間の容量バランスは正極側に大きく傾き、充電時に正極から離脱したリチウムイオンが負極に吸蔵しきれず、過剰になったリチウム金属が負極表面上に析出する問題点があったが、正極板の連結片に樹脂テープが貼着されていることにより、正極から離脱するリチウムイオンを減少させることができ、対向する負極にリチウム金属が析出することが抑制される。また、たとえ析出があった場合にもテープで強固に絶縁できるので短絡が生じない。
【００１２】
上記構成において、樹脂テープは、正極板の巻回方向の約１／２が連結片に粘着しない非粘着面に形成することにより、正極活物質層に樹脂テープが粘着したことによって折り曲げ時に正極活物質層の移動を拘束することがなく、折り曲げ時に連結片内側の正極活物質層は圧縮されて瘤状にならず、集電体に引き延ばし方向の力が加わることが抑制される。
【００１３】
また、本願第２発明は、正極集電体の両面に正極活物質層が形成された正極板材料を用いて複数の正極積層面を連結片で連結して帯状に形成した正極板と、負極集電体の両面に負極活物質層が形成された負極板材料を用いて複数の負極積層面を連結片で連結して帯状に形成した負極板とを、前記正極積層面と前記負極積層面とがセパレータを介して交互に積層されるように前記連結片で折り曲げて扁平に巻回した極板群が、封口ケースにガスケットを介してキャップケースを被せて形成される内部空間に収容されてなる扁平形電池において、前記負極板の巻き始め側端部が最内周部分に配置され、該負極板の巻き始め側端部を包み込むように前記正極板の最も巻き始め側に位置する連結片が配置されて、前記負極板と前記正極板とが巻回されてなり、前記負極板の巻き始め側端部を包み込む前記正極板の最も巻き始め側に位置する連結片と、これに対向する負極板の巻き始め側端部との間に介在するセパレータに、セパレータに存在する細孔を塞ぐ細孔封止処理が施されてなることを特徴とするものである。
【００１４】
上記第２発明によれば、正極板の巻き始め側の連結片は負極板の巻き始め端を包み込むように配置されるので、正極−負極間の容量バランスは正極側に大きく傾き、充電時に正極から離脱したリチウムイオンが負極に吸蔵しきれず、過剰になったリチウム金属が負極表面上に析出する問題点があったが、正極板の連結片に対向する部分のセパレータの細孔を塞ぐことにより、正極から離脱したリチウムイオンがセパレータを通過しないので、負極板の巻き始め端に吸蔵されるリチウムイオンが減少し、負極板にリチウム金属が析出することが抑制される。従って、リチウム金属の析出に起因する充放電サイクル寿命の低下や内部短絡の発生を改善することができる。
【００１５】
上記構成における細孔封止処理は、セパレータの一部分に細孔に侵入して、細孔を塞ぐ塗剤を塗布する処理、セパレータの一部分を熱溶融させて細孔を塞ぐ処理、セパレータの一部分に樹脂テープを貼着する処理のいずれかを適用することができる。
【００１６】
【発明の実施の形態】
以下、添付図面を参照して本発明の実施形態について説明し、本発明の理解に供する。尚、以下に示す実施形態は本発明を具体化した一例であって、本発明の技術的範囲を限定するものではない。
【００１７】
本実施形態に係るコイン形電池は、図１に示すように、円形半殻体に形成された封口ケース５内に極板群１０を収容し、極板群１０から引き出された正極リード２６をキャップケース４に、負極リード２７を封口ケース５にそれぞれ溶接し、封口ケース５内に電解液を注入し、封口ケース５の側周部に配設されたガスケット６上にキャップケース４を被せ、キャップケース４の開口端を内側に折り曲げるカシメ加工により内部空間を封止して構成されたものである。
【００１８】
前記極板群１０は、図２（ａ）に示すように、銅箔である負極集電体の両面に負極活物質層を形成した負極板材料を用いて、図２（ａ）に示すように、６枚の負極積層面２３ａ〜２３ｆを負極連結片２５ａ〜２５ｅで連結し、巻き終り端に負極リード２７が形成された負極板１２と、アルミニウム箔である正極集電体の両面に正極活物質層を形成した正極板材料を用いて、図２（ｂ）に示すように、負極積層面２３ａ〜２３ｆの面積より小さい面積に形成された５枚の正極積層面２２ａ〜２２ｅを正極連結片２４ａ〜２４ｄで連結し、巻き終り端に正極リード２６が形成された正極板１１とをセパレータを介して扁平に巻回して構成される。正極積層面２２ａ〜２２ｅと負極積層面２３ａ〜２３ｆとがセパレータを介して交互に積層されるように巻回するために、正極連結片２４ａ〜２４ｄ及び負極連結片２５ａ〜２５ｅは、図示するように巻き始め側から巻き終わり側に向けて幅が順次増加するように形成されている。また、負極板１２の巻き始め側と巻き終わり側とには小さい径の負極位置ずれ検出孔４３、４４が形成され、負極位置ずれ検出孔４３、４４が形成された負極積層面２３ａ、２３ｆに対面する正極板１１の正極積層面２２ａ、２２ｂ、２２ｅには大きい径の正極位置ずれ検出孔４１ａ、４１ｂ、４２が形成されており、巻回後に負極位置ずれ検出孔４３、４４と正極積層面２２ａ、２２ｂ、２２ｅの一致をＸ線検査することにより、扁平に巻回したときの巻きずれが検出できるようにしている。
【００１９】
図３は、上記正極板１１と負極板１２とをセパレータ１３を介して扁平に巻回した状態を模式図として示すもので、正極板１１の各正極連結片２４ａ〜２４ｄと負極板１２の各負極連結片２５ａ〜２５ｅとを折り曲げて巻回することにより、正極積層面２２ａ〜２２ｅと負極積層面２３ａ〜２３ｆとがセパレータ１３を介して交互に積層されている。このように正極板１１と負極板１２とを扁平に巻回したとき、正極板１１の巻き始め側に位置する正極連結片２４ａと、負極板１２の巻き始め側に位置する負極連結片２５ａとは、小さい曲げ半径で１８０度に折り曲げられることになる。前述したように正極板１１の正極集電体として用いられるアルミニウム箔は曲げ強度、引っ張り強度が低く、小さい曲げ半径で折り曲げられると、折り曲げの内側にある正極活物質層が圧縮され、その外側の正極集電体には引っ張り方向の力が加わって破断する恐れがあった。
【００２０】
この正極集電体の破断を防止し、加えてデンドライトの発生を抑制し、また絶縁性を高めるために、図２（ｂ）に示すように、正極板１１の巻き始め側の正極連結片２４ａには、これが折り曲げられたときに内側となる面に絶縁性樹脂により形成された樹脂テープ４５が貼着されている。樹脂テープ４５が貼着された正極連結片２４ａは、図４に示すように、負極板１２の巻き始め端を包み込むように折り曲げられるので小さい折り曲げ半径となり、鋭角に折り曲げられると、正極連結片２４ａの内側に存在する正極活物質層１１ｂは圧縮され、正極集電体１１ａであるアルミニウムに引き延ばし方向に力が作用するため、正極集電体１１ａが破断する恐れがある。しかし、内側に存在する正極活物質層１１ｂの表面に樹脂テープ４５が貼着されていることにより、樹脂テープ４５の厚さ分だけ正極連結片２４ａの折り曲げ半径が大きくなり、また、鋭角に折り曲げられることがなくなるので、正極集電体１１ａの破断を防止し、加えてデンドライトの発生を抑制し、また、絶縁性を高めることができる。
【００２１】
樹脂テープ４５の貼着は、正極板１１の長さ方向の約１／２に粘着面がない状態にすることが好ましく、貼着によって正極活物質層１１ｂを拘束することがなく、正極連結片２４ａの折り曲げ時に正極活物質層１１ｂが圧縮されて瘤状に膨らむことを規制しない。正極活物質層１１ｂが圧縮されて逃げ場がない状態では、正極集電体１２ａに引っ張り方向の力が及んで破断させることになるが、粘着面を少なくすることによって正極活物質層１１ｂの動きを規制することがない。樹脂テープ４５の粘着面を部分的に無くす方法は、樹脂テープ４５に部分的に粘着剤を塗布する方法でも可能であるが、図５に示すように、樹脂テープ４５をその一方端から粘着面側に折り返し、約１／２が粘着面どうしで粘着して粘着面を覆ってしまう方法が適している。
【００２２】
また、樹脂テープ４５は、その材質としてリチウムイオンの透過を阻害するイオン不透過性を有するもので、非水溶媒に対する化学的な安定性を有するものが望ましい。この樹脂テープ４５が正極連結片２４ａ上に貼着されていることによって、正極連結片２４ａから離脱するリチウムイオンを減少させることができる。負極板１２の巻き始め側の端部は正極連結片２４ａに包み込まれているため、容量バランスが正極側に大きく傾き、充電時に正極から離脱したリチウムイオンが負極に吸蔵しきれず、過剰なリチウムイオンがリチウム金属として負極表面上に析出し、リチウム金属の析出に起因する充放電サイクル特性及び安全性の低下が問題となるが、負極板１２の端部を包み込む正極連結片２４ａに樹脂テープ４５が貼着されていることにより、正極連結片２４ａから離脱するリチウムイオンを減少させ、対向する負極板１２にリチウム金属が析出することを抑制することができる。
【００２３】
上記リチウム金属の析出は、図６に示すように、セパレータ１３の負極板１２の巻き始め側の端部と正極板１１の正極連結片２４ａとの間に位置する部分４７に、細孔封止処理を施すことによっても抑制することができる。セパレータ１３は電解液を保持し、イオン導電性を阻害しないため充分な開孔面積を有するポリオレフィン系樹脂による微多孔膜が用いられているので、セパレータ１３の負極板１２の巻き始め側の端部と正極板１１の正極連結片２４ａとの間に位置する部分の細孔を閉じることにより、正極連結片２４ａから負極板の端部に移動するリチウムイオンを制限することができ、負極板１２上にリチウム金属が析出することを抑制することができる。
【００２４】
前記細孔封止処理は、セパレータ１３に侵入して、細孔を塞ぐ塗剤をセパレータ１３の負極板１２の巻き始め側の端部と正極板１１の正極連結片２４ａとの間に位置する部分４７に塗布する方法、セパレータ１３の負極板１２の巻き始め側の端部と正極板１１の正極連結片２４ａとの間に位置する部分４７を熱溶融させて細孔を塞ぐ方法、セパレータ１３の負極板１２の巻き始め側の端部と正極板１１の正極連結片２４ａとの間に位置する部分４７に樹脂テープを貼着する方法を適用することができる。但し、これらの細孔封止処理によって正極板１１の巻き始め側の正極連結片２４ａに破断が生じるのを防止する作用は期待できない。
【００２５】
【発明の効果】
以上の説明の通り本発明によれば、巻回構造の極板群を用いて扁平形状に二次電池を構成するとき、扁平に極板群を巻回すると巻き始め側の極板の折り曲げ部分に破断が生じる問題を、樹脂テープを貼着する簡単な手段で解決することができる。また、樹脂テープの貼着によりリチウムデンドライトの発生も抑制することができる。このリチウムデンドライトの発生はセパレータの細孔を樹脂テープの貼着や樹脂の塗布などの細孔封止処理によっても抑制することができる。
【図面の簡単な説明】
【図１】扁平形電池の構成を示す断面図。
【図２】（ａ）は負極板、（ｂ）は正極板を示す展開図。
【図３】極板群の巻回状態を示す模式図。
【図４】樹脂テープの貼着状態を示す部分断面図。
【図５】樹脂テープの貼着方法を示す部分断面図。
【図６】セパレータに細孔封止処理を施した構成を示す部分断面図。
【図７】従来の（ａ）は負極板、（ｂ）は正極板を示す展開図。
【図８】従来の極板群の巻回状態を示す模式図。
【図９】従来のコイン形電池の断面図。
【符号の説明】
１０極板群
１１正極板
１２負極板
１３セパレータ
２２ａ〜２２ｅ正極積層面
２３ａ〜２３ｆ負極積層面
２４ａ〜２４ｄ正極連結片
２５ａ〜２５ｅ負極連結片
４５樹脂テープ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coin-type battery and a method for manufacturing the same, and more particularly, to a coin-type battery in which a discharge current is increased by using an electrode plate group having a winding structure in which a positive electrode plate and a negative electrode plate are wound via a separator. Is.
[0002]
[Prior art]
As shown in FIG. 9, the coin-type battery generally employs an electrode plate structure in which a positive electrode pellet 32 and a negative electrode pellet 33 formed in a disk shape are arranged to face each other with a separator 34 interposed therebetween. In this coin-type battery, a positive electrode pellet 32 and a negative electrode pellet 33 are arranged to face each other through a separator 34 in a sealing case 35 formed in a circular half-shell, and an electrolyte is injected into the side peripheral portion of the sealing case 35. A gasket 36 is disposed, and a cap case 31 is placed thereon, and the inner space is hermetically sealed by caulking that bends the open end of the cap case 31 inward to form a battery having a coin-shaped appearance.
[0003]
In the electrode plate structure in which the positive electrode pellet 32 and the negative electrode pellet 33 face each other as described above, it is possible to obtain a large discharge capacity due to factors such as a small reaction area between the positive electrode plate and the negative electrode plate. could not. In order to obtain a large discharge capacity, it is necessary to increase the facing area between the positive electrode plate and the negative electrode plate. In a relatively large battery other than a coin-type battery, a plurality of positive electrode plates and negative electrode plates are laminated via a separator. A structure in which the reaction area is expanded and the energy density in high-rate discharge is improved by a laminated structure or a winding structure in which a strip-like positive electrode plate and negative electrode plate are wound via a separator is widely used. If an electrode plate having such a laminated structure or a wound structure can be accommodated in a coin-shaped flat case, the discharge capacity of the coin-shaped battery can be increased. Batteries in which a wound electrode plate group is housed in a flat case like a coin shape have been proposed by the present applicant as Japanese Patent Application Nos. 2000-241678, 2000-241679, and others.
[0004]
As shown in FIG. 7, the electrode plate group of this winding structure includes a positive electrode plate 7 in which a plurality of positive electrode laminated surfaces 17 a to 17 e are connected by connecting pieces 19 a to 19 d in order to accommodate the circular case. As schematically shown in FIG. 8, a separator 9 is interposed between a negative electrode plate 8 in which a plurality of negative electrode laminate surfaces 18 a to 18 f formed in a larger area than the positive electrode laminate surfaces 17 a to 17 e are connected by connecting pieces 20 a to 20 e. The electrode plate group 1 is formed by winding it flatly. By using this electrode group 1, it is possible to contribute to miniaturization and high functionality of portable electronic devices and the like as a battery that can take out a large discharge current while being small and flat.
[0005]
[Problems to be solved by the invention]
However, when the positive electrode plate 7 and the negative electrode plate 8 are wound flatly, the connecting piece 19a of the positive electrode plate 7 and the connecting piece 20a of the negative electrode plate 8 which are the folding positions closest to the winding start are bent at 180 degrees with a small bending radius. Therefore, breakage may occur in the current collector that is the core material of the electrode plate. In particular, the positive electrode plate 7 uses an aluminum foil as a current collector, and breakage tends to occur because of its low breaking strength.
[0006]
The positive electrode plate 7 has a positive electrode active material layer coated on both sides of the positive electrode current collector. When the positive electrode plate 7 is bent at 180 degrees with a small bending radius by the connecting piece 19a, the inner positive electrode active material layer is compressed. Since the outer positive electrode active material layer is stretched, a force acts in the direction of stretching the positive electrode current collector, and the positive electrode current collector of aluminum foil having a low breaking strength may be broken.
[0007]
In addition, when the flat battery is configured as a lithium ion secondary battery, a transition metal oxide such as lithium cobaltate is used as the positive electrode active material, and a carbon material such as graphite capable of inserting and extracting lithium ions as the negative electrode active material. Is used. In a secondary battery using such a positive electrode active material and a negative electrode active material, the potential of the graphite-based material at the time of charging is used at a low potential that is not substantially different from the potential at which lithium deposition occurs. For this reason, in a secondary battery in which the negative electrode active material has deteriorated due to repeated charge / discharge cycles, etc., lithium ions inserted into the negative electrode active material during charging cause an inactivation reaction with the electrolytic solution, and the surface of the negative electrode plate 8 is inactivated. It is known that a phenomenon in which dendritic lithium metal is deposited occurs, and the internal short circuit resulting from the phenomenon causes the safety and life of the secondary battery to decrease. Compared to the case of a cylindrical battery in which a positive electrode plate and a negative electrode plate are wound in a cylindrical shape, when the electrode plate group is configured by flatly winding like the flat battery of the present invention, the lithium dendrite is It was discovered that it occurs with few charge / discharge cycles.
[0008]
Even when the electrode group is wound in a cylindrical shape or in a flat shape, the area of the facing electrode plate is almost equal, and the capacity between the positive electrode and the negative electrode is kept substantially the same. Yes. However, when the electrode plate group is formed flat, the end portion on the winding start side of the negative electrode plate 8 is opposed to be wrapped in the connecting piece 19a on the winding start side of the positive electrode plate 7, and the end portion is opposed to the end portion. When limited, the capacity balance between the positive electrode and the negative electrode is greatly inclined toward the positive electrode side. For this reason, it was found that lithium ions released from the positive electrode during charging could not be occluded between the carbon material layers of the negative electrode, and excess lithium ions were deposited on the negative electrode surface.
[0009]
The present invention was devised in view of the above problems that occur when a flat plate group is formed by winding flatly, and has a structure that prevents breakage and lithium dendrite from occurring in a current collector during winding. An object is to provide a flat battery.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the first invention of the present application uses a positive electrode plate material in which a positive electrode active material layer is formed on both sides of a positive electrode current collector, and a plurality of positive electrode laminate surfaces are connected with connecting pieces to form a strip shape. A positive electrode plate and a negative electrode plate formed in a strip shape by connecting a plurality of negative electrode laminate surfaces with connecting pieces using a negative electrode plate material having negative electrode active material layers formed on both sides of a negative electrode current collector, the positive electrode laminate surface And an electrode plate group formed by covering the sealing case with a cap case via a gasket so that the negative electrode laminate surface and the negative electrode laminate surface are alternately laminated via separators. In the flat battery accommodated in the space, the winding start side end of the negative electrode plate is disposed at the innermost peripheral portion, and the winding start side of the positive electrode plate is wrapped most around the winding start side end of the negative electrode plate A connecting piece located on the negative electrode plate and the It is a plate is wound, the negative electrode plate winding start side end portion most winding start the wider than the width of the connecting piece insulating the inner surface of the coupling piece located on the side of the resin tape of the positive electrode plate encasing the Is characterized by being attached.
[0011]
According to the first aspect of the present invention, when the positive electrode plate and the negative electrode plate are wound flatly via the separator, the connecting piece located on the most winding start side is bent with a small bending radius. In the current collector, especially the positive electrode plate, when the aluminum foil is used for the current collector, the current collector may be broken by pulling due to bending, but a resin tape is stuck on the inner surface side where the connecting piece is folded Therefore, the bending radius is increased by the thickness of the resin tape, and it is not bent at an acute angle. Therefore, even when aluminum foil is used as the current collector of the positive electrode plate, the current collector is not damaged by bending. it can. Further, since the connecting piece on the winding start side of the positive electrode plate is disposed so as to wrap around the winding start end portion of the negative electrode plate, if limited to the end portion, this end portion is exposed to the cut surface of the current collector. As a result, the capacity balance between the positive electrode and the negative electrode is greatly inclined to the positive electrode side, and lithium ions released from the positive electrode during charging cannot be stored in the negative electrode, and excess lithium metal is deposited on the negative electrode surface. However, since the resin tape is adhered to the connecting piece of the positive electrode plate, lithium ions released from the positive electrode can be reduced, and the deposition of lithium metal on the opposing negative electrode is suppressed. Moreover, even if there is precipitation, a short circuit does not occur because it can be firmly insulated with tape.
[0012]
In the above configuration, the resin tape is formed on the non-adhesive surface in which about 1/2 of the winding direction of the positive electrode plate does not adhere to the connecting piece, so that the positive electrode active material is bent when the resin tape adheres to the positive electrode active material layer. The movement of the material layer is not constrained, and the positive electrode active material layer inside the connecting piece is not compressed and formed into a lump shape at the time of bending, and it is suppressed that a force in the extending direction is applied to the current collector.
[0013]
The second invention of the present application also includes a positive electrode plate formed in a strip shape by connecting a plurality of positive electrode laminate surfaces with connecting pieces using a positive electrode plate material having a positive electrode active material layer formed on both surfaces of a positive electrode current collector, and a negative electrode Using the negative electrode plate material in which the negative electrode active material layer is formed on both surfaces of the current collector, the negative electrode plate formed in a strip shape by connecting a plurality of negative electrode laminate surfaces with connecting pieces, the positive electrode laminate surface and the negative electrode laminate surface Doo is electrode plate group that has been the wound flatly folded by a connecting piece to be laminated alternately through the separator, are accommodated in an internal space formed by covering a cap case via a gasket to the sealing case In the flat battery, the winding start side end of the negative electrode plate is disposed at the innermost peripheral portion, and the connection located on the most winding start side of the positive electrode plate so as to wrap around the winding start side end of the negative electrode plate A piece is placed and the negative electrode plate and the positive electrode plate are wound. Becomes, the separator interposed between the the connecting piece located closest to the winding start side of the positive electrode plate encasing winding start side end portion of the negative electrode plate, a winding start-side end portion of the negative electrode plate opposed thereto, the separator It is characterized by being subjected to a pore sealing process for closing the pores existing in the film.
[0014]
According to the second aspect of the invention, since the connecting piece on the winding start side of the positive electrode plate is disposed so as to wrap around the winding start end of the negative electrode plate, the capacity balance between the positive electrode and the negative electrode is greatly inclined toward the positive electrode side, and the positive electrode is charged during charging. Lithium ions released from the anode could not be occluded in the negative electrode, and excess lithium metal was deposited on the negative electrode surface, but by closing the pores of the separator facing the connecting piece of the positive electrode plate, Since the lithium ions released from the positive electrode do not pass through the separator, the lithium ions occluded at the winding start end of the negative electrode plate are reduced, and the deposition of lithium metal on the negative electrode plate is suppressed. Accordingly, it is possible to improve the decrease in charge / discharge cycle life and the occurrence of internal short circuit due to the deposition of lithium metal.
[0015]
The pore sealing process in the above configuration is a process of applying a coating agent that penetrates into a part of the separator and plugs the pores, a process of thermally melting a part of the separator to close the pores, and a part of the separator. Any of the processes of sticking the resin tape can be applied.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
[0017]
As shown in FIG. 1, the coin-type battery according to the present embodiment accommodates the electrode plate group 10 in a sealing case 5 formed in a circular half-shell, and has a positive electrode lead 26 drawn out from the electrode plate group 10. The cap case 4 is welded with the negative electrode lead 27 to the sealing case 5, the electrolyte is injected into the sealing case 5, and the cap case 4 is placed on the gasket 6 disposed on the side periphery of the sealing case 5, The inner space is sealed by caulking that bends the opening end of the cap case 4 inward.
[0018]
As shown in FIG. 2 (a), the electrode plate group 10 uses a negative electrode plate material in which a negative electrode active material layer is formed on both surfaces of a negative electrode current collector that is a copper foil, as shown in FIG. 2 (a). In addition, six negative electrode laminate surfaces 23a to 23f are connected by negative electrode connecting pieces 25a to 25e, and a negative electrode plate 12 having a negative electrode lead 27 formed at the end of winding and a positive electrode on both surfaces of a positive electrode current collector that is an aluminum foil. Using the positive electrode plate material on which the active material layer is formed, as shown in FIG. 2B, the five positive electrode laminate surfaces 22a to 22e formed in an area smaller than the area of the negative electrode laminate surfaces 23a to 23f are connected to the positive electrode. It connects with the piece 24a-24d, and the positive electrode plate 11 in which the positive electrode lead 26 was formed at the end of winding was wound flatly via a separator. In order to wind so that the positive electrode laminated surfaces 22a to 22e and the negative electrode laminated surfaces 23a to 23f are alternately laminated via the separator, the positive electrode connecting pieces 24a to 24d and the negative electrode connecting pieces 25a to 25e are illustrated as shown in the figure. The width is formed so as to increase sequentially from the winding start side to the winding end side. Further, negative electrode position deviation detection holes 43 and 44 having a small diameter are formed on the winding start side and the winding end side of the negative electrode plate 12, and the negative electrode lamination surfaces 23a and 23f on which the negative electrode position deviation detection holes 43 and 44 are formed are formed. The positive electrode laminate surfaces 22a, 22b, and 22e of the positive electrode plate 11 facing each other are formed with large-diameter positive electrode misalignment detection holes 41a, 41b, and 42, and the negative electrode misalignment detection holes 43 and 44 and the positive electrode laminate surface after winding. The X-ray inspection of the coincidence of 22a, 22b and 22e makes it possible to detect the winding deviation when it is wound flat.
[0019]
FIG. 3 schematically shows a state in which the positive electrode plate 11 and the negative electrode plate 12 are flatly wound via the separator 13. Each positive electrode connecting piece 24 a to 24 d of the positive electrode plate 11 and each of the negative electrode plate 12 are shown in FIG. By bending and winding the negative electrode connecting pieces 25 a to 25 e, the positive electrode stacked surfaces 22 a to 22 e and the negative electrode stacked surfaces 23 a to 23 f are alternately stacked via the separator 13. Thus, when the positive electrode plate 11 and the negative electrode plate 12 are wound flatly, the positive electrode connection piece 24a positioned on the winding start side of the positive electrode plate 11, and the negative electrode connection piece 25a positioned on the winding start side of the negative electrode plate 12 Is bent at 180 degrees with a small bending radius. As described above, the aluminum foil used as the positive electrode current collector of the positive electrode plate 11 has low bending strength and tensile strength. When the aluminum foil is bent with a small bending radius, the positive electrode active material layer inside the bending is compressed, The positive electrode current collector may be broken due to the force in the pulling direction.
[0020]
In order to prevent breakage of the positive electrode current collector and to suppress the generation of dendrites and to improve insulation, the positive electrode connecting piece 24a on the winding start side of the positive electrode plate 11, as shown in FIG. Is attached with a resin tape 45 formed of an insulating resin on the inner surface when it is bent. As shown in FIG. 4, the positive electrode connecting piece 24a to which the resin tape 45 is attached is bent so as to wrap around the winding start end of the negative electrode plate 12, so that it has a small bending radius. When the positive electrode connecting piece 24a is bent at an acute angle, the positive electrode connecting piece 24a Since the positive electrode active material layer 11b existing inside is compressed and a force acts in the extending direction on the aluminum that is the positive electrode current collector 11a, the positive electrode current collector 11a may be broken. However, since the resin tape 45 is attached to the surface of the positive electrode active material layer 11b existing inside, the bending radius of the positive electrode connecting piece 24a is increased by the thickness of the resin tape 45, and the positive electrode active material layer 11b is bent at an acute angle. Therefore, the positive electrode current collector 11a can be prevented from being broken, in addition, generation of dendrites can be suppressed, and insulation can be improved.
[0021]
The sticking of the resin tape 45 is preferably in a state where there is no adhesive surface in about ½ of the length direction of the positive electrode plate 11, and the positive electrode active material layer 11b is not restrained by the sticking, and the positive electrode connecting piece The positive electrode active material layer 11b is not restricted from being compressed and swollen in the shape of a bump when being bent at 24a. In a state where the positive electrode active material layer 11b is compressed and there is no escape place, the positive electrode current collector 12a is subjected to a force in the pulling direction to be broken, but the movement of the positive electrode active material layer 11b is reduced by reducing the adhesive surface. There is no regulation. The method of partially eliminating the adhesive surface of the resin tape 45 is also possible by a method of partially applying an adhesive to the resin tape 45, but as shown in FIG. A method of folding back to the side and covering the adhesive surface by adhering about 1/2 of the adhesive surfaces to each other is suitable.
[0022]
Moreover, the resin tape 45 has an ion impermeability that inhibits the permeation of lithium ions as its material, and preferably has a chemical stability against a non-aqueous solvent. By sticking this resin tape 45 on the positive electrode connecting piece 24a, lithium ions released from the positive electrode connecting piece 24a can be reduced. Since the end portion on the winding start side of the negative electrode plate 12 is encased in the positive electrode connecting piece 24a, the capacity balance is greatly inclined to the positive electrode side, and lithium ions released from the positive electrode during charging cannot be occluded in the negative electrode, and excessive lithium ions Is deposited on the surface of the negative electrode as lithium metal, and there is a problem of charge / discharge cycle characteristics and safety deterioration due to the deposition of lithium metal. However, the resin tape 45 is attached to the positive electrode connection piece 24a that wraps the end of the negative electrode plate 12. By sticking, the lithium ion which detach | leaves from the positive electrode connection piece 24a can be decreased, and it can suppress that lithium metal precipitates on the negative electrode plate 12 which opposes.
[0023]
As shown in FIG. 6, the lithium metal is deposited in a pore 47 at a portion 47 located between the end portion of the separator 13 on the winding start side of the negative electrode plate 12 and the positive electrode connecting piece 24 a of the positive electrode plate 11. It can suppress also by processing. Since the separator 13 retains the electrolytic solution and does not hinder ionic conductivity, a microporous film made of a polyolefin resin having a sufficient aperture area is used. Therefore, the end of the separator 13 on the winding start side of the negative electrode plate 12 is used. By closing the pores located between the positive electrode plate 11 and the positive electrode connecting piece 24a, the lithium ions moving from the positive electrode connecting piece 24a to the end of the negative electrode plate can be restricted. It is possible to suppress the precipitation of lithium metal.
[0024]
In the pore sealing process, the coating material that enters the separator 13 and closes the pores is positioned between the end of the separator 13 on the winding start side of the negative electrode plate 12 and the positive electrode connecting piece 24a of the positive electrode plate 11. A method of applying to the portion 47, a method of thermally melting the portion 47 located between the winding start side end of the negative electrode plate 12 of the separator 13 and the positive electrode connecting piece 24a of the positive electrode plate 11, and closing the pores; A method of applying a resin tape to the portion 47 located between the end of the negative electrode plate 12 on the winding start side and the positive electrode connecting piece 24a of the positive electrode plate 11 can be applied. However, the effect of preventing breakage of the positive electrode connecting piece 24a on the winding start side of the positive electrode plate 11 by these pore sealing processes cannot be expected.
[0025]
【The invention's effect】
As described above, according to the present invention, when the secondary battery is configured in a flat shape using the electrode group having a winding structure, when the electrode group is wound in a flat shape, a bent portion of the electrode plate on the winding start side is formed. Can be solved by a simple means of sticking a resin tape. Moreover, generation | occurrence | production of lithium dendrite can also be suppressed by sticking of a resin tape. The generation of this lithium dendrite can also be suppressed by pore sealing treatment such as sticking a resin tape or applying a resin.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a flat battery.
FIG. 2A is a development view showing a negative electrode plate and FIG. 2B showing a positive electrode plate.
FIG. 3 is a schematic diagram showing a winding state of an electrode plate group.
FIG. 4 is a partial cross-sectional view showing a state where a resin tape is attached.
FIG. 5 is a partial cross-sectional view showing a method for attaching a resin tape.
FIG. 6 is a partial cross-sectional view showing a configuration in which a separator is subjected to pore sealing treatment.
7A and 7B are development views showing a conventional negative electrode plate and FIG. 7B a positive electrode plate, respectively.
FIG. 8 is a schematic view showing a winding state of a conventional electrode plate group.
FIG. 9 is a cross-sectional view of a conventional coin battery.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Electrode plate group 11 Positive electrode plate 12 Negative electrode plate 13 Separator 22a-22e Positive electrode laminated surface 23a-23f Negative electrode laminated surface 24a-24d Positive electrode connection piece 25a-25e Negative electrode connection piece 45 Resin tape

Claims

Using a positive electrode plate material having a positive electrode active material layer formed on both sides of a positive electrode current collector, a positive electrode plate formed by connecting a plurality of positive electrode laminate surfaces with connecting pieces and formed into a strip shape, and a negative electrode active material on both sides of the negative electrode current collector A negative electrode plate formed by connecting a plurality of negative electrode laminate surfaces with connecting pieces using a negative electrode plate material on which a material layer is formed, and the positive electrode laminate surface and the negative electrode laminate surface are alternately arranged via separators. In the flat battery in which the electrode plate group that is folded flatly by the connecting piece so as to be laminated is accommodated in an internal space formed by covering the sealing case with a cap case via a gasket,
A winding start side end portion of the negative electrode plate is disposed at an innermost peripheral portion, and a connecting piece located at the most winding start side of the positive electrode plate is disposed so as to wrap around the winding start side end portion of the negative electrode plate, The negative electrode plate and the positive electrode plate are wound,
An insulating resin tape wider than the width of the connecting piece is attached to the inner surface side of the connecting piece positioned on the most winding start side of the positive electrode plate that wraps around the winding start side end of the negative electrode plate. Flat battery.

The flat battery according to claim 1, wherein the resin tape is formed on a non-adhesive surface in which about 1/2 of the winding direction of the positive electrode plate does not adhere to the connecting piece.

Using a positive electrode plate material having a positive electrode active material layer formed on both sides of a positive electrode current collector, a positive electrode plate formed by connecting a plurality of positive electrode laminate surfaces with connecting pieces and formed into a strip shape, and a negative electrode active material on both sides of the negative electrode current collector A negative electrode plate formed by connecting a plurality of negative electrode laminate surfaces with connecting pieces using a negative electrode plate material on which a material layer is formed, and the positive electrode laminate surface and the negative electrode laminate surface are alternately arranged via separators. electrode group was wound flatly folded at the connecting piece so as to be stacked in flat-shaped battery comprising housed in an internal space formed by covering a cap case via a gasket to the sealing case,
A winding start side end portion of the negative electrode plate is disposed at an innermost peripheral portion, and a connecting piece located at the most winding start side of the positive electrode plate is disposed so as to wrap around the winding start side end portion of the negative electrode plate, The negative electrode plate and the positive electrode plate are wound,
Present in the separator is a separator interposed between the connecting piece located on the most winding start side of the positive electrode plate that wraps around the winding start side end portion of the negative electrode plate and the winding start side end portion of the negative electrode plate opposed thereto. A flat battery characterized by being subjected to a pore sealing process for closing the pores.

The flat battery according to claim 3, wherein the pore sealing treatment is performed by applying a coating agent that penetrates into a part of the pores of the separator and blocks the pores.

The flat battery according to claim 3, wherein the pore sealing process closes the pores by thermally melting a part of the separator.

The flat battery according to claim 3, wherein the pore sealing treatment is performed by attaching a resin tape to a part of the separator.