JP3680768B2

JP3680768B2 - Assembled battery

Info

Publication number: JP3680768B2
Application number: JP2001182711A
Authority: JP
Inventors: 亮小島; 竹規石津
Original assignee: Shin Kobe Electric Machinery Co Ltd
Current assignee: Shin Kobe Electric Machinery Co Ltd
Priority date: 2001-06-18
Filing date: 2001-06-18
Publication date: 2005-08-10
Anticipated expiration: 2021-06-18
Also published as: JP2002373633A

Description

【０００１】
【発明の属する技術分野】
本発明は組電池に係り、特に、活物質にリチウムマンガン複合酸化物を用いた平板状の正極と、活物質に黒鉛を用いた平板状の負極とが積層状態で電池缶内に収容された角型非水電解液二次電池を、複数個配列した組電池に関する。
【０００２】
【従来の技術】
近年、再充電可能な二次電池の分野では、鉛電池、ニッケル−カドミウム電池、ニッケル−水素電池等の水溶液系電池が主流であった。しかしながら、電気機器の小型化、軽量化が進むにつれ、体積効率に優れた非水電解液二次電池が着目され、その研究、開発及び商品化が急速に進められるに至っている。また、地球温暖化や枯渇燃料の問題から、電気自動車やハイブリッド電気自動車が各自動車メーカーで開発され、その電源用に高容量の非水電解液二次電池も求められている。
【０００３】
このような非水電解液二次電池は、その組立容易性から大半が円筒型の二次電池であり、充放電での活物質の膨張収縮による電池の膨れが問題になるほど多数枚の平板状電極を積層した非水電解液二次電池を組電池に用いる際の技術的問題点が提起されている公知例は少ない。また、それらの公知例においても、例えば特開平７−１２２２５２号公報に開示されているように、活物質の膨張収縮による電池の膨れにはあまり着目せず、放熱と電池性能（サイクル特性、放熱特性など）上の問題から、電池と電池との間に放熱を兼ねる保持部材を配し、組電池全体の拘束にはバネ部材を用いて電池及び電池の中に存在する極板群に対する加圧を保っているに留まる。
【０００４】
【発明が解決しようとする課題】
しかしながら、活物質にリチウムマンガン複合酸化物を用いた平板状の正極と、活物質に黒鉛を用いた平板状の負極を積層した角型非水電解液二次電池では、充放電に伴う活物質の不可逆な膨張収縮によって電池は徐々に膨れを生ずる。この角型非水電解液二次電池を用いて組電池を構成するときに、組電池の体積効率を向上させるため、角型非水電解液二次電池同士を密着させてかつ隙間なく枠体を取りつけた場合、角型非水電解液二次電池自身の膨れにより組電池全体の体積が増加し枠体の破断が起こる可能性がある。一方、枠体の破断を防止するために、特開平７−１２２２５２号公報の技術のように、バネ部材及び保持部材を使用すると、電池の膨れによる枠体の破断を防止し安全性を確保することはできるが、組電池全体の体積が増加するので、体積効率が低下してしまう、という問題点がある。
【０００５】
本発明は、上記事案に鑑み、体積効率及び安全性に優れた組電池を提供することを課題とする。
【０００６】
【課題を解決するための手段】
上記課題を解決するために、本発明は、活物質にリチウムマンガン複合酸化物を用いた平板状の正極と、活物質に黒鉛を用いた平板状の負極とが積層状態で電池缶内に収容された角型非水電解液二次電池を、複数個配列した組電池において、前記角型非水電解液二次電池の配列方向が前記正負極の積層方向と一致しており、前記角型非水電解液二次電池間の間隔の合計が前記角型非水電解液二次電池の配列方向の合計の厚さの２％以上であり、前記角型非水電解液二次電池は前記配列方向に固定された枠体との摩擦力によって該枠体内で摺動可能に保持されていることを特徴とする。
【０００７】
本発明者らは、活物質にリチウムマンガン複合酸化物を用いた平板状の正極と、活物質に黒鉛を用いた平板状の負極とが積層状態で電池缶内に収容された角型非水電解液二次電池の配列方向の厚さが、実用上使用限界となる電池容量の劣化が起こるまでに、使用前の角型非水電解液二次電池の配列方向の厚さに比べ２％程度膨れることを発見した。
【０００８】
本発明では、角型非水電解液二次電池を配列するときに、角型非水電解液二次電池間の間隔の合計を、角型非水電解液二次電池の配列方向の合計の厚さの２％以上確保するようにしたので、充放電により角型非水電解液二次電池が膨れても、角型非水電解液二次電池が使用限界になるまで組電池全体の体積が増加することはなく、安全性に優れた組電池を得ることができる。また、角型非水電解液二次電池間の間隔の合計を角型非水電解液二次電池の配列方向の合計の厚さの２％程度に抑えることで、ほぼ角型非水電解液二次電池同士が密着した状態にできるので、体積効率にも優れた組電池を得ることができる。更に、複数個の角型非水電解液二次電池を、角型非水電解液二次電池の配列方向に固定された枠体との摩擦力によって該枠体内で摺動可能に保持することで、各角型非水電解液二次電池の膨れに偏りがあるときにも、角型非水電解液二次電池の膨れに対応して摩擦力に打ち勝って枠体内で移動する。
【００１０】
【発明の実施の形態】
以下、図面を参照して、本発明をハイブリッド電気自動車（ＨＥＶ）搭載用の組電池に適用した実施の形態について説明する。
【００１１】
図１に示すように、本実施形態の組電池１は、枠体としての組電池枠の中に８個の角型非水電解液二次電池２が配設されている。図２に示すように、組電池枠１０は、二次電池２の底部に配置される底板３、二次電池２の上部に配置される上枠５、底板３及び上枠５の側面に配置される２枚の側板４、並びに、上枠５の上部を覆う枠蓋６により枠状に構成されている。
【００１２】
底板３は、アルミニウム製平板であり、長手方向に沿って両端部が断面Ｌ字状に折り曲げられており、上面側には複数箇所肉抜き加工が施されている。側板４は、二次電池２の長側面とほぼ同一寸法のアルミニウム製平板である。上枠５は、８個の二次電池２の上部が突出可能な開口が形成されたアルミニウム製枠であり、長手方向に沿って両端部が断面Ｌ字状に折り曲げられている。また、枠蓋６は、矩形キャップ状の成形樹脂であり、長手方向の一側両端部に略正方形状の枠蓋開口部６ａが形成されている。
【００１３】
図３に示すように、二次電池２は、正極、負極及びセパレータが角型状の有底電池缶１６内に収容されている。電池缶１６は、ステンレス板をレーザ溶接で貼り合せて作製されており、上端部の開口が矩形状のステンレス製上蓋１７で封口されている。上蓋１７の略中央には、非水電解液の注液後にネジを螺着するためのネジ穴１３が形成されている。ネジ穴１３の両側には、ステンレス製薄膜で電池の内圧上昇時に外部にガスを開放する安全弁１４が配設されている。更に、安全弁１４の外側で電池缶１６の長手方向両端部側には、それぞれ六角形状の正極端子１２及び負極端子１５が電池缶１６と絶縁されて電池缶１６から上方に突出している。正極端子１２及び負極端子１５は、後述するように、電池缶１６内部でそれぞれ正極及び負極との接触が保たれている。
【００１４】
図４に示すように、電池缶１６内には、袋状セパレータ２３で覆われた正極２１と負極２２とが、交互に複数枚積層されている。正極２１は、リチウムマンガン複酸化物（例えば、マンガン酸リチウム）粉末を導電材の炭素材料と共に、ＰＶｄＦ（ポリフッ化ビニリデン）をＮＭＰ（ｎ−メチルピロリドン）に溶解したバインダ溶液に、リチウムマンガン複酸化物：炭素材料：ＰＶｄＦの固形分比が９０：５：５となるように混合し、攪拌して正極スラリを得て、これを集電体のアルミニウム箔に均一に塗布し乾燥させて、集電のため一部を残してアルミニウム箔を切り取り、プレス加工して所定の寸法に成型し、電池缶に合わせた寸法に裁断して得られたものである。なお、集電のために残した部分には、短冊状の正極集電タブが形成されている。
【００１５】
負極２２は、ＰＶｄＦをＮＭＰに溶解したバインダ溶液に黒鉛粉末を、黒鉛粉末：ＰＶｄＦの固形分比が９０：１０になるように混合し、攪拌して負極スラリを得て、これを集電体の銅箔に均一に塗布し乾燥させて、集電のため一部を残して銅箔を切り取り、プレス加工して所定の寸法に成型し、電池缶に合わせた寸法に裁断して得られたものである。なお、集電のために残した部分には、短冊状の負極集電タブが形成されている。
【００１６】
セパレータ２３は、リチウムイオンの通過を許容するポリエチレン製微多孔薄膜であり、有底袋体とされている。正極２１を覆うセパレータ２３にはシャットダウン特性に優れたセパレータが用いられており、負極２２を覆うセパレータ２３にはメルトダウン特性に優れたセパレータが用いられている。正負極集電タブは、正極２１及び負極２２をそれぞれ正極端子１２及び負極端子１５に接続する図示しないストラップに超音波溶接で固定されている。
【００１７】
電池缶１６には、セパレータ２３で覆われた正極２１、負極２２が積層されて収容された後、非水電解液が注入される。非水電解液には、例えば、エチルカーボネート、ジエチルカーボネート及びジメチルカーボネートを混合した溶媒に、六フッ化リン酸リチウムを溶解した電解質溶液が用いられている。この注入作業は、乾燥Ａｒで置換したドライボックス中で行われ、ネジ穴１３を開いたままの状態で電池容量の１５％程度初充電をして、副反応により発生するガスが開放される。ネジ穴１３は、シール材を介してネジが螺着されて封口される。なお、電池缶１６は、上蓋１７の上面の正極端子１２及び負極端子１５を含むほぼ全面及び電池缶１６の底面の一部を除いて、絶縁のための収縮チューブで被覆されている。
【００１８】
図１に示すように、組電池１には、８個の二次電池２が、正極２１、負極２２の積層方向（底板３の長手方向）に配列されている。各二次電池２間に形成された間隔の合計（以下、総間隔という。）は、二次電池２の積層方向の合計の厚さ（以下、総電池厚さという。）の２％以上が確保されている。すなわち、一側の側板４の内側の面から他側の側板４の内側の面までの長さを長さＡ、積層方向の二次電池２の厚さを厚さＢ、とすると、両者には下記式（１）の関係がある。なお、図１では、一例として間隔７、８、９の大きさがそれぞれ異なる例を示した。
【００１９】
【数１】

【００２０】
また、底板３及び上枠５の長手方向の両端部と、側板４の上下面と、にはネジ穴が形成されており、ネジを螺着することで底板３、上枠５及び２枚の側板４が一体となって固定されている。８個の二次電池２の上部は上枠５から突出している。また、二次電池２は、底板３の上面、底面３のＬ字状に折り曲げられた内側部分、及び、上枠５のＬ字状に折り曲げられた内側部分に接触しており、この接触による摩擦力によって保持されている。なお、組電池１内で８個の二次電池２は図示しない接続部材で正極端子１２、負極端子１５が隣接する二次電池２に接続されており、両端部に配置される二次電池２の正極端子１２、負極端子１５が枠蓋６に形成された枠蓋開口部６ａから突出している。枠蓋６は上枠５に固定されている。
【００２１】
次に、本実施形態の組電池１の作用について説明する。組電池１は、総間隔が総電池厚さの２％以上確保されているので、二次電池２が使用限界になるまで充放電により二次電池２が２％程度膨れても、組電池枠１０が破断する程の圧力が加えられることがないため、安全性に優れた組電池１とすることができる。また、総間隔を総電池厚さの２％程度とすることにより、ほぼ二次電池２を密着した状態にできるので、体積効率の優れた組電池とすることができる。また、二次電池２を配列するときに、任意の二次電池２間に間隔を形成してもよいので、組立作業効率を向上させることができる。
【００２２】
また、組電池１では、二次電池２が、底板３の上面、底板３の内側部分、及び、上枠５の内側部分との接触による摩擦力によって保持されているので、二次電池２の膨れに偏りがあるときにも、二次電池２は個々に組電池枠１０内を摺動でき、二次電池２の膨れに対応して摩擦力に打ち勝って組電池枠１０内で移動し側板４間内に配置される。
【００２３】
更に、本実施形態では、底板３の上面に肉抜き加工が施されているので、組電池１を軽量化することができる。
【００２４】
なお、本実施形態において、総間隔が総電池厚さの２％以上必要であることは、実用上使用限界となる電池容量の劣化が起こるまでの電池の膨れから経験的に決定したものである。電池の膨れは、充電時に負極の黒鉛の層間にリチウムイオンがインターカレーションして層間化合物を形成することに起因する。電池の膨れの大きさは、活物質（黒鉛）の結晶格子の変形の度合いを示す変形レベルで定義することはできるが、この変形が電池の膨れに影響する度合いは、二次電池の場合、負極活物質の密度、正極、負極及びセパレータの積層枚数、電解液の組成、充放電パターンなど多岐に渡る因子によるので、結晶格子の変形から電池の膨れの大きさを計算しても、実用上意味がない。
【００２５】
また、本実施形態では、二次電池２を間隔７、８、９を形成して配列した例を示したが、二次電池２間に少なくとも１箇所以上間隔を形成して、総間隔が総電池厚さの２％以上であれば、この間隔を個々の電池の間に形成してもよいし、配列する二次電池２の全数より少ない任意の複数個の電池を密着して配置し他の電池との間にまとめて形成してもよい。各二次電池２を離間させて（間隔を形成して）、電池缶１６と外気とが接触する面積を増加させることで、冷却効果を向上させるようにしてもよい。
【００２６】
また、本実施形態では、組電池枠１０が底板３、側板４、上枠５及び枠蓋６で構成されている例を示したが、材質、部品数、形状はこれらに限定されるものではなく、電池を摩擦力で保持できればよいので、例えば材質はステンレス等の金属製としてもよいし、上板５はＬ字状に折り曲げられなくてもよく、底板３は箱状に作製してもよい。また、側板４に肉抜き加工を施すようにしてもよい。
【００２７】
【実施例】
次に、本実施形態に従って作製した実施例の組電池１について説明する。なお、比較のために作製した比較例の組電池についても併記する。
【００２８】
（実施例１〜３）
各実施例では、図５に示すように、厚さ４０ｍｍの二次電池２間をそれぞれ１．２ｍｍ、１．１ｍｍ、１．０ｍｍの間隔７として、二次電池２の合計の厚さ３２０ｍｍに対して合計それぞれ８．４ｍｍ、７．７ｍｍ、７．０ｍｍの間隔が形成された組電池１を作製した。
【００２９】
（比較例１〜３）
各比較例では、各二次電池２間をそれぞれ０．９ｍｍ、０．５ｍｍ、０ｍｍとし、間隔合計をそれぞれ６．３ｍｍ、３．５ｍｍ、０ｍｍとして、組電池枠が取り付けられている以外は、実施例と同様に組電池を作製した。
【００３０】
＜試験・評価＞
次に、以上のように作製した実施例及び比較例の各組電池について、それぞれ３個ずつ満充電又は放電するまでに８時間を要する電流値で、電池容量の７０％の充放電を１０００サイクル繰り返し、組電池の状態を目視観察した。下表１に目視観察の結果を示す。
【００３１】
【表１】

【００３２】
表１に示すように、実施例１〜３の組電池１では、１０００サイクルの充放電後においても、組電池枠１０の破損は見られなかった。これに対して、比較例１〜３の組電池では、組電池枠が３個中２個破損した。
【００３３】
実施例の組電池１の二次電池２が、充放電による正負極活物質の不可逆な膨張収縮によって膨れても、総間隔が総電池厚さの２％程度確保されているので、組電池枠１０が破断しないような構造となっている。また、各電池は電池缶１６（電池缶１６を被覆する絶縁チューブ）と組電池枠１０との摩擦によって保持されているので、電池の膨れが不均一な場合でも電池自身の膨れによって各電池が最も適切な位置に摺動するので、電池の膨れの総和が一定以下である限りは組電池枠１０が破断しない。更に、電池の膨れが１ｍｍ以上となるまでは、電池間に間隔が存在することになるので、外気による空冷効果も期待できる。
【００３４】
【発明の効果】
以上説明したように、本発明によれば、角型非水電解液二次電池を配列するときに、角型非水電解液二次電池間の間隔の合計を、角型非水電解液二次電池の配列方向の合計の厚さの２％以上確保するようにしたので、角型非水電解液二次電池が使用限界になるまで組電池全体の体積が増加することはなく、安全性に優れた組電池を得ることができ、角型非水電解液二次電池間の間隔の合計を角型非水電解液二次電池の配列方向の合計の厚さの２％程度に抑えることで、ほぼ角型非水電解液二次電池同士が密着した状態にできるので、体積効率にも優れた組電池を得ることができると共に、角型非水電解液二次電池は配列方向に固定された枠体との摩擦力によって該枠体内で摺動可能に保持されているので、各角型非水電解液二次電池の膨れに偏りがあるときにも、角型非水電解液二次電池の膨れに対応して摩擦力に打ち勝って枠体内で移動することができる、という効果を得ることができる。
【図面の簡単な説明】
【図１】本発明が適用可能な実施形態の組電池の正面図である。
【図２】実施形態の組電池の組電池枠の分解斜視図である。
【図３】実施形態の組電池を構成する二次電池の斜視図である。
【図４】二次電池の正極、負極及びセパレータの概略構成及び積層方向を示す斜視図である。
【図５】実施例の組電池の正面図である。
【符号の説明】
１組電池
２角型非水電解液二次電池
３底板（枠体の一部）
４側板（枠体の一部）
５上枠（枠体の一部）
６枠蓋（枠体の一部）
６ａ枠蓋開口部（枠体の一部）
７、８、９間隔
１０組電池枠（枠体）
２１正極
２２負極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an assembled battery, and in particular, a flat positive electrode using a lithium manganese composite oxide as an active material and a flat negative electrode using graphite as an active material are housed in a battery can in a stacked state. The present invention relates to an assembled battery in which a plurality of prismatic non-aqueous electrolyte secondary batteries are arranged.
[0002]
[Prior art]
In recent years, in the field of rechargeable secondary batteries, aqueous batteries such as lead batteries, nickel-cadmium batteries, and nickel-hydrogen batteries have been mainstream. However, as electric appliances have become smaller and lighter, non-aqueous electrolyte secondary batteries with excellent volume efficiency have attracted attention, and their research, development, and commercialization have been rapidly promoted. In addition, due to global warming and depleted fuel problems, electric vehicles and hybrid electric vehicles have been developed by automobile manufacturers, and high-capacity non-aqueous electrolyte secondary batteries are also required for their power sources.
[0003]
Such non-aqueous electrolyte secondary batteries are mostly cylindrical secondary batteries because of their ease of assembly, and the number of flat plates is so large that the expansion of the battery due to expansion and contraction of the active material during charging and discharging becomes a problem. There are few known examples in which technical problems have been raised when a non-aqueous electrolyte secondary battery in which electrodes are laminated is used in an assembled battery. Also in these known examples, as disclosed in, for example, Japanese Patent Application Laid-Open No. 7-122252, little attention is paid to the swelling of the battery due to the expansion and contraction of the active material, and the heat dissipation and the battery performance (cycle characteristics, heat dissipation). Due to problems in characteristics, etc., a holding member that also dissipates heat is placed between the batteries, and a spring member is used to constrain the entire assembled battery, and pressure is applied to the battery and the electrode plate group existing in the battery. Stay in the
[0004]
[Problems to be solved by the invention]
However, in a prismatic non-aqueous electrolyte secondary battery in which a plate-like positive electrode using lithium manganese composite oxide as an active material and a plate-like negative electrode using graphite as an active material are stacked, the active material accompanying charge / discharge Due to this irreversible expansion and contraction, the battery gradually expands. In order to improve the volume efficiency of the assembled battery when the assembled battery is configured using this rectangular non-aqueous electrolyte secondary battery, the rectangular non-aqueous electrolyte secondary battery is brought into close contact with each other without any gaps. May cause the volume of the entire assembled battery to increase due to the swelling of the square nonaqueous electrolyte secondary battery itself, and the frame body may break. On the other hand, when a spring member and a holding member are used as in the technique of JP-A-7-122252 in order to prevent the frame body from being broken, the frame body is prevented from being broken due to battery swelling to ensure safety. However, since the volume of the entire assembled battery increases, there is a problem that the volume efficiency is lowered.
[0005]
In view of the above case, an object of the present invention is to provide an assembled battery excellent in volume efficiency and safety.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention accommodates a flat positive electrode using lithium manganese composite oxide as an active material and a flat negative electrode using graphite as an active material in a battery can in a stacked state. In an assembled battery in which a plurality of prismatic non-aqueous electrolyte secondary batteries are arranged, the arrangement direction of the prismatic non-aqueous electrolyte secondary battery coincides with the stacking direction of the positive and negative electrodes, der 2% or more the thickness of the total sum of the intervals in the arrangement direction of the angle type nonaqueous electrolyte secondary battery among the nonaqueous electrolyte secondary battery is, the angle non-aqueous electrolyte secondary battery characterized that you have been slidably held in the frame body by friction between the fixed frame in the arrangement direction.
[0007]
The inventors of the present invention have disclosed a rectangular non-aqueous solution in which a flat positive electrode using lithium manganese composite oxide as an active material and a flat negative electrode using graphite as an active material are housed in a battery can in a stacked state. The thickness of the electrolyte secondary battery in the arrangement direction is 2% of the thickness in the arrangement direction of the prismatic non-aqueous electrolyte secondary battery before use until the battery capacity deteriorates, which is the practical limit of use. I discovered that it swelled to a certain extent.
[0008]
In the present invention, when arranging the prismatic non-aqueous electrolyte secondary batteries, the total interval between the prismatic non-aqueous electrolyte secondary batteries is the total of the arrangement directions of the prismatic non-aqueous electrolyte secondary batteries. Since 2% or more of the thickness is secured, even if the prismatic nonaqueous electrolyte secondary battery swells due to charging / discharging, the volume of the entire assembled battery until the prismatic nonaqueous electrolyte secondary battery reaches the limit of use. Is not increased, and an assembled battery excellent in safety can be obtained. In addition, by suppressing the total interval between the prismatic nonaqueous electrolyte secondary batteries to about 2% of the total thickness in the arrangement direction of the prismatic nonaqueous electrolyte secondary batteries, the prismatic nonaqueous electrolyte is substantially Since the secondary batteries can be brought into close contact with each other, an assembled battery having excellent volume efficiency can be obtained. Furthermore, a plurality of prismatic nonaqueous electrolyte secondary batteries are slidably held within the frame body by frictional force with the frame bodies fixed in the arrangement direction of the prismatic nonaqueous electrolyte secondary battery. Thus, even when each of the square non-aqueous electrolyte secondary batteries is unevenly swollen, the frictional force is overcome corresponding to the swelling of the square non-aqueous electrolyte secondary battery, and the square non-aqueous electrolyte secondary battery moves within the frame.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to an assembled battery for mounting on a hybrid electric vehicle (HEV) will be described with reference to the drawings.
[0011]
As shown in FIG. 1, the assembled battery 1 of this embodiment has eight square non-aqueous electrolyte secondary batteries 2 arranged in an assembled battery frame as a frame. As shown in FIG. 2, the assembled battery frame 10 is disposed on the bottom plate 3 disposed at the bottom of the secondary battery 2, the upper frame 5 disposed on the upper portion of the secondary battery 2, and the side surfaces of the bottom plate 3 and the upper frame 5. The two side plates 4 and the frame lid 6 that covers the upper portion of the upper frame 5 are configured in a frame shape.
[0012]
The bottom plate 3 is a flat plate made of aluminum, and both end portions thereof are bent in an L-shaped cross section along the longitudinal direction, and a plurality of portions are cut out on the upper surface side. The side plate 4 is an aluminum flat plate having substantially the same dimensions as the long side surface of the secondary battery 2. The upper frame 5 is an aluminum frame in which an opening from which the upper part of the eight secondary batteries 2 can project is formed, and both end portions are bent in an L-shaped cross section along the longitudinal direction. The frame lid 6 is a rectangular cap-shaped molding resin, and a substantially square frame lid opening 6a is formed at one end on one side in the longitudinal direction.
[0013]
As shown in FIG. 3, in the secondary battery 2, the positive electrode, the negative electrode, and the separator are accommodated in a square bottomed battery can 16. The battery can 16 is made by laminating stainless plates by laser welding, and the upper end opening is sealed with a rectangular stainless steel upper lid 17. A screw hole 13 for screwing a screw after injecting the non-aqueous electrolyte is formed in the approximate center of the upper lid 17. On both sides of the screw hole 13, a safety valve 14 made of a stainless steel thin film is provided to release gas to the outside when the internal pressure of the battery increases. Furthermore, the hexagonal positive electrode terminal 12 and the negative electrode terminal 15 are insulated from the battery can 16 and protrude upward from the battery can 16 on both ends in the longitudinal direction of the battery can 16 outside the safety valve 14. The positive electrode terminal 12 and the negative electrode terminal 15 are kept in contact with the positive electrode and the negative electrode, respectively, inside the battery can 16 as will be described later.
[0014]
As shown in FIG. 4, a plurality of positive electrodes 21 and negative electrodes 22 covered with a bag-like separator 23 are alternately stacked in the battery can 16. The positive electrode 21 is composed of a lithium manganese complex oxide (for example, lithium manganate) powder in a binder solution obtained by dissolving PVdF (polyvinylidene fluoride) in NMP (n-methylpyrrolidone) together with a carbon material as a conductive material. The mixture was mixed so that the solid content ratio of the product: carbon material: PVdF was 90: 5: 5 and stirred to obtain a positive electrode slurry, which was uniformly applied to the aluminum foil of the current collector and dried. The aluminum foil was cut out, partly left for electricity, pressed, molded into a predetermined size, and cut into a size matched to the battery can. In addition, a strip-like positive electrode current collecting tab is formed in a portion left for current collection.
[0015]
The negative electrode 22 was prepared by mixing graphite powder with a binder solution obtained by dissolving PVdF in NMP so that the solid content ratio of graphite powder: PVdF was 90:10 and stirring to obtain a negative electrode slurry. The copper foil was uniformly applied to the copper foil and dried, and the copper foil was cut out, leaving a part for current collection, press-molded into a predetermined size, and cut into a size suitable for the battery can. Is. A strip-shaped negative electrode current collecting tab is formed in a portion left for current collection.
[0016]
The separator 23 is a polyethylene microporous thin film that allows passage of lithium ions, and is a bottomed bag. A separator excellent in shutdown characteristics is used for the separator 23 covering the positive electrode 21, and a separator excellent in meltdown characteristics is used for the separator 23 covering the negative electrode 22. The positive and negative current collecting tabs are fixed by ultrasonic welding to a strap (not shown) that connects the positive electrode 21 and the negative electrode 22 to the positive electrode terminal 12 and the negative electrode terminal 15, respectively.
[0017]
After the positive electrode 21 and the negative electrode 22 covered with the separator 23 are stacked and accommodated in the battery can 16, a non-aqueous electrolyte is injected. As the non-aqueous electrolyte, for example, an electrolyte solution in which lithium hexafluorophosphate is dissolved in a solvent in which ethyl carbonate, diethyl carbonate, and dimethyl carbonate are mixed is used. This injection operation is performed in a dry box substituted with dry Ar, and the initial charge is made about 15% of the battery capacity with the screw hole 13 kept open, and the gas generated by the side reaction is released. The screw hole 13 is sealed by screwing a screw through a sealing material. The battery can 16 is covered with a shrinkable tube for insulation except for almost the entire surface including the positive electrode terminal 12 and the negative electrode terminal 15 on the upper surface of the upper lid 17 and a part of the bottom surface of the battery can 16.
[0018]
As shown in FIG. 1, in the assembled battery 1, eight secondary batteries 2 are arranged in the stacking direction of the positive electrode 21 and the negative electrode 22 (longitudinal direction of the bottom plate 3). The total distance formed between the secondary batteries 2 (hereinafter referred to as total distance) is 2% or more of the total thickness in the stacking direction of the secondary batteries 2 (hereinafter referred to as total battery thickness). It is secured. That is, if the length from the inner surface of the side plate 4 on one side to the inner surface of the side plate 4 on the other side is length A and the thickness of the secondary battery 2 in the stacking direction is thickness B, Has the relationship of the following formula (1). FIG. 1 shows an example in which the

intervals

7, 8, and 9 have different sizes as an example.
[0019]
[Expression 1]

[0020]
In addition, screw holes are formed in both end portions of the bottom plate 3 and the upper frame 5 in the longitudinal direction and upper and lower surfaces of the side plate 4, and the bottom plate 3, the upper frame 5, and the two sheets can be formed by screwing screws. The side plate 4 is fixed integrally. The upper parts of the eight secondary batteries 2 protrude from the upper frame 5. Further, the secondary battery 2 is in contact with the upper surface of the bottom plate 3, the inner portion of the bottom surface 3 that is bent into an L shape, and the inner portion of the upper frame 5 that is bent into an L shape. It is held by frictional force. In the assembled battery 1, the eight secondary batteries 2 are connected to the adjacent secondary battery 2 with the positive electrode terminal 12 and the negative electrode terminal 15 being connected members (not shown), and the secondary batteries 2 arranged at both ends. The positive electrode terminal 12 and the negative electrode terminal 15 protrude from a frame lid opening 6 a formed in the frame lid 6. The frame lid 6 is fixed to the upper frame 5.
[0021]
Next, the effect | action of the assembled battery 1 of this embodiment is demonstrated. The assembled battery 1 has a total interval of 2% or more of the total battery thickness, so even if the secondary battery 2 expands by about 2% by charge / discharge until the secondary battery 2 reaches the use limit, the assembled battery frame Since no pressure is applied to the extent that 10 is broken, the assembled battery 1 having excellent safety can be obtained. Further, by setting the total interval to about 2% of the total battery thickness, the secondary battery 2 can be brought into close contact with each other, so that an assembled battery with excellent volume efficiency can be obtained. Further, when arranging the secondary batteries 2, an interval may be formed between any secondary batteries 2, so that the assembly work efficiency can be improved.
[0022]
In the assembled battery 1, the secondary battery 2 is held by frictional force due to contact with the upper surface of the bottom plate 3, the inner portion of the bottom plate 3, and the inner portion of the upper frame 5. Even when the swelling is biased, the secondary batteries 2 can individually slide in the assembled battery frame 10, overcome the frictional force corresponding to the swelling of the secondary battery 2, move in the assembled battery frame 10, and move to the side plate. 4 is arranged in between.
[0023]
Furthermore, in the present embodiment, since the upper surface of the bottom plate 3 is subjected to the blanking process, the assembled battery 1 can be reduced in weight.
[0024]
In the present embodiment, the fact that the total interval is required to be 2% or more of the total battery thickness is determined empirically from the swelling of the battery until the battery capacity is degraded, which is a practical limit of use. . The swelling of the battery is caused by lithium ions intercalating between the graphite layers of the negative electrode during charging to form an intercalation compound. The size of the battery bulge can be defined by a deformation level indicating the degree of deformation of the crystal lattice of the active material (graphite), but the degree of the influence of the deformation on the battery bulge is in the case of a secondary battery. Because it depends on various factors such as the density of the negative electrode active material, the number of layers of the positive electrode, the negative electrode and the separator, the composition of the electrolyte, and the charge / discharge pattern, it is practical even if the size of the battery bulge is calculated from the deformation of the crystal lattice meaningless.
[0025]
Further, in the present embodiment, an example in which the secondary batteries 2 are arranged with

intervals

7, 8, and 9 shown is shown. However, at least one interval is formed between the secondary batteries 2 so that the total interval is the total. If the thickness is 2% or more of the battery thickness, this interval may be formed between the individual batteries, or any number of batteries smaller than the total number of the secondary batteries 2 to be arranged may be in close contact with each other. You may form together between these batteries. The cooling effect may be improved by separating each secondary battery 2 (by forming an interval) and increasing the area where the battery can 16 and the outside air contact.
[0026]
Moreover, in this embodiment, although the assembled battery frame 10 showed the example comprised by the baseplate 3, the side plate 4, the upper frame 5, and the frame cover 6, the material, the number of parts, and a shape are not limited to these. For example, the material may be made of metal such as stainless steel, the upper plate 5 may not be bent in an L shape, and the bottom plate 3 may be formed in a box shape. Good. Further, the side plate 4 may be subjected to a blanking process.
[0027]
【Example】
Next, the assembled battery 1 of the Example produced according to this embodiment is demonstrated. In addition, it describes together about the assembled battery of the comparative example produced for the comparison.
[0028]
(Examples 1-3)
In each example, as shown in FIG. 5, the interval between the secondary batteries 2 having a thickness of 40 mm is set to an interval 7 of 1.2 mm, 1.1 mm, and 1.0 mm, respectively, so that the total thickness of the secondary batteries 2 is 320 mm. On the other hand, a battery pack 1 having a total distance of 8.4 mm, 7.7 mm, and 7.0 mm was produced.
[0029]
(Comparative Examples 1-3)
In each comparative example, the interval between the secondary batteries 2 is 0.9 mm, 0.5 mm, and 0 mm, respectively, and the total distance is 6.3 mm, 3.5 mm, and 0 mm, respectively, except that the assembled battery frame is attached. An assembled battery was produced in the same manner as in the example.
[0030]
<Test and evaluation>
Next, for each of the assembled batteries of Examples and Comparative Examples produced as described above, three cycles of charging and discharging 70% of the battery capacity at a current value that takes 8 hours to fully charge or discharge each three batteries. Repeatedly, the state of the assembled battery was visually observed. Table 1 below shows the results of visual observation.
[0031]
[Table 1]

[0032]
As shown in Table 1, in the assembled battery 1 of Examples 1 to 3, the assembled battery frame 10 was not damaged even after 1000 cycles of charge and discharge. On the other hand, in the assembled batteries of Comparative Examples 1 to 3, two of the assembled battery frames were damaged.
[0033]
Even if the secondary battery 2 of the assembled battery 1 of the embodiment swells due to irreversible expansion and contraction of the positive and negative electrode active materials due to charge and discharge, the total interval is secured about 2% of the total battery thickness. The structure is such that 10 does not break. In addition, since each battery is held by friction between the battery can 16 (insulating tube covering the battery can 16) and the assembled battery frame 10, even when the battery does not swell unevenly, Since the battery slides to the most appropriate position, the assembled battery frame 10 does not break as long as the sum of the swelling of the batteries is below a certain level. Furthermore, since there is an interval between the batteries until the swelling of the battery becomes 1 mm or more, an air cooling effect by the outside air can be expected.
[0034]
【The invention's effect】
As described above, according to the present invention, when the prismatic non-aqueous electrolyte secondary batteries are arranged, the sum of the intervals between the prismatic non-aqueous electrolyte secondary batteries is set to the square non-aqueous electrolyte secondary battery. Since the total thickness in the secondary battery array direction is 2% or more, the total volume of the assembled battery does not increase until the square non-aqueous electrolyte secondary battery reaches the limit of use. The total distance between the prismatic nonaqueous electrolyte secondary batteries can be suppressed to about 2% of the total thickness in the arrangement direction of the prismatic nonaqueous electrolyte secondary batteries. Therefore, since the prismatic nonaqueous electrolyte secondary batteries can be brought into close contact with each other, an assembled battery with excellent volume efficiency can be obtained , and the prismatic nonaqueous electrolyte secondary batteries are fixed in the arrangement direction. Since it is slidably held in the frame body by the frictional force with the formed frame body, each square type non-aqueous electrolyte secondary battery is swollen. When also Rigaaru can move the frame body overcomes the frictional force corresponding to the bulging of the square nonaqueous electrolyte secondary battery, the effect can be obtained as.
[Brief description of the drawings]
FIG. 1 is a front view of an assembled battery according to an embodiment to which the present invention is applicable.
FIG. 2 is an exploded perspective view of an assembled battery frame of the assembled battery according to the embodiment.
FIG. 3 is a perspective view of a secondary battery constituting the assembled battery of the embodiment.
FIG. 4 is a perspective view illustrating a schematic configuration and a stacking direction of a positive electrode, a negative electrode, and a separator of a secondary battery.
FIG. 5 is a front view of the assembled battery of the example.
[Explanation of symbols]
1 Battery 2 Square non-aqueous electrolyte secondary battery 3 Bottom plate (part of the frame)
4 Side plate (part of the frame)
5 Upper frame (part of the frame)
6 Frame lid (part of the frame)
6a Frame lid opening (part of the frame)
7, 8, 9 Interval 10 Assembly battery frame (frame)
21 Positive electrode 22 Negative electrode

Claims

活物質にリチウムマンガン複合酸化物を用いた平板状の正極と、活物質に黒鉛を用いた平板状の負極とが積層状態で電池缶内に収容された角型非水電解液二次電池を、複数個配列した組電池において、前記角型非水電解液二次電池の配列方向が前記正負極の積層方向と一致しており、前記角型非水電解液二次電池間の間隔の合計が前記角型非水電解液二次電池の配列方向の合計の厚さの２％以上であり、前記角型非水電解液二次電池は前記配列方向に固定された枠体との摩擦力によって該枠体内で摺動可能に保持されていることを特徴とする組電池。A prismatic non-aqueous electrolyte secondary battery in which a flat positive electrode using lithium manganese composite oxide as an active material and a flat negative electrode using graphite as an active material are housed in a battery can in a stacked state In the assembled battery, a plurality of square non-aqueous electrolyte secondary batteries are aligned in the same direction as the stacking direction of the positive and negative electrodes, and the total interval between the square non-aqueous electrolyte secondary batteries friction There Ri der least 2% of the total thickness of the arrangement direction of the angle non-aqueous electrolyte secondary battery, wherein the angle non-aqueous electrolyte secondary battery of the frame body fixed to the arrangement direction assembled battery characterized that you have been slidably held in the frame body by the force.