JP4228665B2

JP4228665B2 - Non-aqueous electrolyte secondary battery

Info

Publication number: JP4228665B2
Application number: JP2002337698A
Authority: JP
Inventors: 達也橋本; 優 ▲高▼木; 一成木下; 猛志福政
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2002-11-21
Filing date: 2002-11-21
Publication date: 2009-02-25
Anticipated expiration: 2022-11-21
Also published as: JP2004171979A

Description

【０００１】
【発明の属する技術分野】
本発明は、非水電解液二次電池に関し、特に高温保存後の電池特性ならびに充放電サイクル特性に優れた非水電解液二次電池に関する。
【０００２】
【従来の技術】
従来、ＡＶ機器、ノート型パソコン、或いは携帯型通信機器などの駆動用電源として、ニッケルカドミウム蓄電池やニッケル水素蓄電池が主に用いられていたが、近年では、電子機器のポータブル化やコードレス化が進展して定着するに従って、駆動用電源となる二次電池の高エネルギー密度化や小型軽量化の要望が、ますます強くなっている。このような要望に応える電池として、小型・軽量でありながら急速充電が可能で、高エネルギー密度を有するという極めて顕著な特徴を有するリチウムイオン二次電池に代表される非水電解液二次電池が、開発され主流になっている。
【０００３】
この非水電解液二次電池は、図１に示すように、アルミニウム製の正極集電体１ａにリチウム含有遷移金属化合物、例えばＬｉＣｏＯ₂を正極活物質とする正極合剤層を形成した正極板１と、銅製の負極集電体に炭素材料を負極活物質とする負極合剤層を形成した負極板２とをセパレータ３を介して絶縁した状態で捲回してなる極板群、非水電解液、ならびに前記極板群と非水電解液とを電池ケース４に収納し、リチウムイオンの挿入、離脱を利用した電池であり、充放電サイクル時の膨張、収縮を抑え、充放電サイクル特性を向上させる方法として、最外周部分において、セパレータを熱溶着して固定する方法（例えば、特許文献１参照。）や絶縁部材を貼り付ける方法が提案されている（例えば、特許文献２〜４参照。）。
【０００４】
しかしながら、電子機器の高機能化等に伴い、さらなる高容量化、高エネルギー密度化が強く要望されており、容量に寄与しないセパレータや集電体などを薄くしたり、極板の充填密度を上げているため、充放電サイクル時の発熱が大きくなり、極板群の膨張、収縮を抑えることが困難になっている。
【０００５】
【特許文献１】
特開２００１−１６７７９９号公報
【特許文献２】
特開平１０−２４７５０３号公報
【特許文献３】
特開２０００−２５１８６６号公報
【特許文献４】
特開２００２−１２４２９３号公報
【０００６】
【発明が解決しようとする課題】
本発明は、このような課題に鑑みなされたもので、充放電サイクル時の発熱に伴う極板群の膨張、収縮を抑え、充放電サイクル特性に優れ、信頼性の高い非水電解液二次電池を提供することを主たる目的とする。
【０００７】
【課題を解決するための手段】
上記のような課題を解決するための本発明は、正極板と負極板とをセパレータを介して絶縁した状態で捲回してなる極板群、非水電解液、ならびに前記極板群と非水電解液とを収納する電池ケースからなる非水電解液二次電池において、前記電池ケースと前記正極板の正極合剤層が無く正極集電体とがセパレータを介して対向する領域では正極集電体の上下両端部に対向する位置の前記セパレータ上に絶縁部材が配設されており、この正極集電体と対向している絶縁部材の幅をＳ、正極板幅をＭとしたとき（Ｓ／Ｍ）≦０．２０であることを特徴とする。
【０００８】
【発明の実施の形態】
以下、本発明の実施の形態について、図面を参照しながら説明する。図１に、円筒型リチウム二次電池の主要構成を示す電池断面図、図２（ａ）、（ｂ）にその一部縦断面図を示す。正極板１と負極板２とがセパレータ３を介して絶縁された状態で捲回してなる極板群と非水電解液（図示せず）とが電池ケース４に収納されている。正極板１は、アルミニウム製の箔やラス加工やエッチング処理された箔からなる正極集電体１ａの片側または両面に正極活物質、結着剤、導電剤、必要に応じて増粘剤を溶剤に混練分散させたペースト状の正極合剤を塗布、乾燥、圧延して正極合剤層を形成することができ、その厚みは１００μｍ〜２００μｍの厚みで、柔軟性があることが好ましい。
【０００９】
正極板の最外周は、正極合剤層が無く正極集電体１ａのみで、充放電サイクル時の発熱を電池ケース４を通じて外部に放出させることができる。
【００１０】
正極活物質としては、例えば、リチウムイオンをゲストとして受け入れ得るリチウム含有遷移金属化合物が使用される。例えば、コバルト、マンガン、ニッケル、クロム、鉄およびバナジウムから選ばれる少なくとも一種類の金属とリチウムとの複合金属酸化物、ＬｉＣｏＯ₂、ＬｉＭｎＯ₂、ＬｉＮｉＯ₂、ＬｉＣｏ_xＮｉ_(1-x)Ｏ₂（０＜ｘ＜１）、ＬｉＣｒＯ₂、αＬｉＦｅＯ₂、ＬｉＶＯ₂等が好ましい。
【００１１】
結着剤としては、使用する溶剤や電解液に対して安定な材料であれば、特に限定されないが、例えば、フッ素系結着材やアクリルゴム、変性アクリルゴム、スチレン−ブタジエンゴム（ＳＢＲ）、イソプロピレンゴム、ブタジエンゴム、アクリル系重合体、ビニル系重合体等を単独、或いは二種類以上の混合物または共重合体として用いることができる。フッ素系結着剤としては、例えば、ポリフッ化ビニリデン（ＰＶＤＦ）、フッ化ビニリデン（ＶＤＦ）とヘキサフルオロプロピレン（ＨＦＰ）の共重合体（Ｐ（ＶＤＦ−ＨＦＰ））やポリテトラフルオロエチレン樹脂のディスパージョン等が好ましい。
【００１２】
増粘剤としては、カルボシキメチルセルロース、メチルセルロース、ヒドロキシメチルセルロース、エチルセルロース、ポリビニルアルコール、酸化スターチ、リン酸化スターチ、ガゼイン等が好ましい。
【００１３】
導電剤としては、アセチレンブラック、ファーネスブラック、グラファイト、黒鉛、炭素繊維等を単独、或いは二種類以上の混合物が好ましい。
【００１４】
溶剤としては、結着剤が溶解可能な溶剤が適切で、有機系結着剤の場合は、Ｎ−メチル−２−ピロリドン（ＮＭＰ）、Ｎ，Ｎ−ジメチルホルムアミド、テトラヒドロフラン、ジメチルアセトアミド、ジメチルスルホキシド、ヘキサメチルスルホルアミド、テトラメチル尿素、アセトン、メチルエチルケトン等の有機溶剤を単独またはこれらを混合した混合溶剤が好ましく、水系結着剤の場合は水や温水が好ましい。また、負極板２は、負極集電体の片側または両面に負極活物質と結着剤、必要に応じて増粘剤、導電助剤を溶剤に混練分散させたペースト状の負極合剤を塗布、乾燥、圧延して負極合剤層を形成することができ、その厚みは１００μｍ〜２１０μｍの厚みで、柔軟性があることが好ましい。
【００１５】
負極活物質としては、特に限定されるものではないが、例えば、有機高分子化合物（フェノール樹脂、ポリアクリロニトリル、セルロース等）を焼成することにより得られる炭素材料、コークスやピッチを焼成することにより得られる炭素材料、或いは人造グラファイト、天然グラファイト等が好ましく、その形状としては、球状、鱗片状、塊状のものを用いることができる。
【００１６】
負極集電体として用いる銅または銅合金は、特に限定されるものではなく、圧延箔、電解箔などが挙げられ、その形状も箔、孔開き箔、エキスパンド材、ラス材等であっても構わないが、その厚みは引張り強度が強いほど好ましいが、厚くなると電池内部の空隙体積が少なくなり、エネルギー密度が低下するので２０μｍ以下が好ましく、８〜１５μｍの範囲がより好ましい。
【００１７】
結着剤、溶剤および必要に応じて加えることができる導電助剤は正極の導電剤と同様のものを使用することができる。
【００１８】
ところで、正極および負極の活物質、結着剤、必要に応じて加える導電剤、導電助剤を溶剤に混練分散させてペースト状合剤を作製する方法は、特に限定されるものではなく、例えば、プラネタリーミキサー、ホモミキサー、ピンミキサー、ニーダー、ホモジナイザー等を用いることができる。これらを単独、或いは組み合わせて使用することも可能である。
【００１９】
また、上記ペースト状合剤の混練分散時に、各種分散剤、界面活性剤、安定剤等を必要に応じて添加することも可能である。
【００２０】
塗着乾燥は、特に限定されるものではなく、上記のように混錬分散させたペースト状の合剤を、例えば、スリットダイコーター、リバースロールコーター、リップコーター、ブレードコーター、ナイフコーター、グラビアコーター、ディップコーター等を用いて、容易に塗着することができ、自然乾燥に近い乾燥が好ましいが、生産性を考慮すると７０℃〜２００℃の温度で乾燥させるのが好ましい。
【００２１】
圧延は、ロールプレス機によって所定の厚みになるまで、線圧１０００〜２０００ｋｇ／ｃｍで数回圧延を行うか、線圧を変えて圧延するのが好ましい。
【００２２】
セパレータとしては、ポリエチレン樹脂、ポリプロピレン樹脂などのポリオレフィン樹脂の微多孔膜や不織布からなる単層または多層構造で構成されており、ポリエチレン樹脂とポリプロピレン樹脂の２層または両端がポリプロピレン樹脂で中間層がポリエチレン樹脂の３層構造でシャットダウン機能を有するセパレータが好ましく、セパレータの厚みは１０〜３０μｍの範囲が好ましい。
【００２３】
絶縁部材は基材と糊剤からなり、基材の厚みとしては、２０μｍ〜６０μｍの範囲、糊剤の厚みとしては２０μｍ〜８０μｍの範囲が、絶縁性、貼着性、作業性の観点から好ましい。
【００２４】
絶縁部材の基材の材質としては、ポリエチレン樹脂、ポリプロピレン樹脂などのポリオレフィン樹脂、ポリエチレンテレフタレート樹脂、ポリエーテルエーテルケトン樹脂、ポリフェニレンサルファイド樹脂、ポリアリレート樹脂、ポリアミド樹脂、ポリイミド樹脂、フッ素樹脂などを挙げることができ、これらを単独またはブレンドした樹脂、変性した樹脂を用いることができる。そして、ガラス繊維、タルク、シリカなどの充填材を添加しても良い。
【００２５】
絶縁部材の糊剤としては、天然ゴム、イソブチルゴム、スチレンブタジエンゴム、シリコンゴム、ウレタンゴム、アクリル樹脂などを挙げることができる。これらを単独や積層したものや、変性したものを用いることができる。
【００２６】
このようにして得られる正極板１と負極板２とをセパレータ３を介して絶縁された状態で捲回した極板群の最外周に上端部絶縁部材１１ａおよび下端部絶縁部材１１ｂを配設して電池ケース４に収納する。このとき、上端部絶縁部材１１ａ、下端部絶縁部材１１ｂを配設する位置と幅が重要であり、前記正極板１の正極合剤層が無く正極集電体１ａと電池ケース４とがセパレータ３を介して対向する領域では正極集電体１ａの上下両端部に対向する位置の前記セパレータ３上に上端部絶縁部材１１ａ、下端部絶縁部材１１ｂを配設し、これらの正極集電体１ａと対向している上端部絶縁部材１１ａ、下端部絶縁部材１１ｂの幅の総和をＳ、正極板幅をＭとしたとき（Ｓ／Ｍ）≦０．２０とする。
【００２７】
正極板１の最外周は、正極合剤層が無く正極集電体１ａのみで、充放電サイクル時の発熱を、電池ケース４を通じて外部に放出させることができ、絶縁部材を最外周のセパレータに貼着することにより、極板群の膨張、収縮を抑制することができるが、正極集電体１ａの上下両端部のバリ等によって、電池ケース４と短絡する危険性を回避するために、絶縁部材をこの部分に配設する必要がある。
【００２８】
また、（Ｓ／Ｍ）の比率は０．２０以下が好ましく、０．０５以上、０．２０以下の範囲が最適である。０．２０を超える場合には、充放電時の膨張、収縮を抑える効果が変わらない上、充放電の妨げとなるので好ましくなく、逆に０．０５未満の場合には、充放電時の膨張、収縮を抑える効果がほとんど無いので好ましくない。
【００２９】
ところで、正極板１の最外周を正極合剤層が無く正極集電体１ａのみにし、さらに、図２（ｃ）、（ｄ）に示すように、負極板２の最外周を負極合剤層が無く負極集電体２ａのみにすることにより、充放電サイクル時の発熱をより効率良く、電池ケース４を通じて外部に放出させることができる。
【００３０】
非水電解液としては、非水溶媒と電解質からなり、非水溶媒としては、主成分として環状カーボネートおよび鎖状カーボネートが含有される。前記環状カーボネートとしては、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、およびブチレンカーボネート（ＢＣ）から選ばれる少なくとも一種であることが好ましい。また、前記鎖状カーボネートとしては、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、およびエチルメチルカーボネート（ＥＭＣ）等から選ばれる少なくとも一種であることが好ましい。
【００３１】
電解質としては、例えば、電子吸引性の強いリチウム塩を使用し、例えば、ＬｉＰＦ₆、ＬｉＢＦ₄、ＬｉＣｌＯ₄、ＬｉＡｓＦ₆、ＬｉＣＦ₃ＳＯ₃、ＬｉＮ（ＳＯ₂ＣＦ₃）₂、ＬｉＮ（ＳＯ₂Ｃ₂Ｆ₅）₂、ＬｉＣ（ＳＯ₂ＣＦ₃）₃等が挙げられる。これらの電解質は、一種類で使用しても良く、二種類以上組み合わせて使用しても良い。これらの電解質は、前記非水溶媒に対して０．５〜１．５Ｍの濃度で溶解させることが好ましい。
【００３２】
【実施例】
以下、実施例および比較例を用いて詳細に説明するが、これらは、本発明を何ら限定するものではない。
【００３３】
（実施例１）
正極板１は、正極活物質としてコバルト酸リチウムを１００重量部、導電剤としてアセチレンブラックの炭素粉末を３重量部、結着剤としてポリテトラフルオロエチレン（ＰＴＦＥ）樹脂ディスパージョンを固形分で４重量部、増粘剤としてカルボキシメチルセルロース水溶液を固形分で０．８重量部を混練分散させてペースト状合剤を作製した。このペースト状合剤を、厚さ２０μｍの帯状のアルミニウム箔からなる正極集電体１ａに連続的に間欠塗着を行い乾燥して、厚み２９０μｍの正極板１を作製し、線圧１０００Ｋｇ／ｃｍで３回圧延を行うことにより、正極板厚みを１８０μｍに圧延した。この正極板１の最外周で正極合剤層が無く正極集電体１ａが露出している部分に正極リード７をスポット溶接して取り付けた後、１２０℃で１５分間の正極板乾燥を行った。
【００３４】
次に、負極板は負極活物質としてリチウム箔を吸蔵、放出可能な鱗片状黒鉛１００重量部、結着剤としてスチレンブタジエンゴム（ＳＢＲ）の水溶性ディスパージョンを固形分として４重量部、増粘剤としてカルボキシメチルセルロース水溶液を０．８重量部を混練分散させて、ペースト状合剤を作製した。このペースト状合剤を厚さ１４μｍの帯状の銅箔からなる負極集電体に連続的に間欠塗着を行い乾燥して、厚さ３００μｍの負極板２を作製し、線圧１１０Ｋｇ／ｃｍで３回圧延を行うことにより、負極板厚みを１９６μｍに圧延した。この負極板３の最内周で負極合剤層が無く負極集電体が露出している部分にスポット溶接して負極リード８を取り付けた後、１１０℃で１０分間の負極板乾燥を行った。
【００３５】
このようにして得られた正極板１と負極板２とを耐熱温度が１３８℃で、厚さ２０μｍのポリプロピレン製セパレータ３を介して絶縁した状態で捲回してなる極板群を作製した。
【００３６】
この極板群の図２（ａ）に示すように、幅５７ｍｍの正極板最外周の正極集電体１ａの上端面を被覆するように上端部絶縁部材１１ａを上端部より下方に４．０ｍｍ、上方に２．０ｍｍの位置に対向するように幅６ｍｍの絶縁テープを幅６０ｍｍのセパレータ３の最外周の外側に貼着して配設した。
【００３７】
次に、図２（ｂ）に示すように、正極板最外周の正極集電体１ａの下端面を被覆するように下端部絶縁部材１１ｂを下端部より上方に４．０ｍｍ、下方に２．０ｍｍの位置に対向するように幅６ｍｍの絶縁テープをセパレータ３の最外周の外側に貼着して配設した。
【００３８】
このとき、Ｓ／Ｍ＝（４．０＋４．０）／５７＝０．１４であった。
【００３９】
なお、この上端部絶縁部材１１ａおよび下端部絶縁部材１１ｂは、厚さ４０μｍのポリプロピレン樹脂の基材と厚さ１０μｍのウレタン樹脂の糊剤からなる絶縁テープを用い、隙間が生じないようにオーバーラップさせた。
【００４０】
次に、負極板６から連接する負極リード９を下部絶縁板１０を介して、前記ケース８と電気的に接続し、正極板５から連接する正極リード３を上部絶縁板４を介して、封口板１の内部端子に電気的に接続した後、非水電解液（図示せず）を注液し、封口板５と電池ケース４が絶縁ガスケット６を介してかしめ封口して、直径１８ｍｍ、高さ６５ｍｍサイズで電池容量が２０００ｍＡｈの円筒型リチウムイオン二次電池を作製し、電池Ａとした。
【００４１】
なお電解液は、エチレンカーボネート３０体積％、エチルメチルカーボネート５０体積％、プロピオン酸メチル２０体積％の混合溶媒中に、電解質としてヘキサフルオロリン酸リチウム（ＬｉＰＦ₆）を１．０モル溶かした電解液を所定量注液した。この電解液は、正極活物質層および負極活物質層内に含浸されて、電池反応において、微多孔膜のセパレータを通して正極板１と負極板２間のＬｉイオンの移動を担う。
【００４２】
（実施例２）
正極板最外周の正極集電体１ａの上端面を被覆するように上端部絶縁部材１１ａを上端部より下方に６．０ｍｍ、上方に１．５ｍｍの位置に対向するように幅７．５ｍｍの絶縁テープをセパレータ３の最外周の外側に貼着して配設し、正極板最外周の正極集電体１ａの下端面を被覆するように下端部絶縁部材１１ｂを下端部より上方に５．４ｍｍ、下方に１．６ｍｍの位置に対向するように幅７．０ｍｍの絶縁テープをセパレータ３の最外周の外側に貼着して配設した以外は実施例１と同様にして円筒型リチウムイオン二次電池を作製し、Ｓ／Ｍ＝（６．０＋５．４）／５７＝０．２０となる電池Ｂとした。
【００４３】
（実施例３）
正極板最外周の正極集電体１ａの上端面を被覆するように上端部絶縁部材１１ａを上端部より下方に１．３ｍｍ、上方に１．２ｍｍの位置に対向するように幅２．５ｍｍの絶縁テープをセパレータ３の最外周の外側に貼着して配設し、正極板最外周の正極集電体１ａの下端面を被覆するように下端部絶縁部材１１ｂを下端部より上方に１．５ｍｍ、下方に１．５ｍｍの位置に対向するように幅３．０ｍｍの絶縁テープをセパレータ３の最外周の外側に貼着して配設した以外は実施例１と同様にして円筒型リチウムイオン二次電池を作製し、Ｓ／Ｍ＝（１．３＋１．５）／５７＝０．０５となる電池Ｃとした。
【００４４】
（比較例１）
正極板最外周の正極集電体１ａの上端面を被覆するように上端部絶縁部材１１ａを上端部より下方に８．５ｍｍ、上方に１．５ｍｍの位置に対向するように幅１０ｍｍの絶縁テープをセパレータ３の最外周の外側に貼着して配設し、正極板最外周の正極集電体１ａの下端面を被覆するように下端部絶縁部材１１ｂを下端部より上方に８．５ｍｍ、下方に１．５ｍｍの位置に対向するように幅１０ｍｍの絶縁テープをセパレータ３の最外周の外側に貼着して配設した以外は実施例１と同様にして円筒型リチウムイオン二次電池を作製し、Ｓ／Ｍ＝（８．５＋８．５）／５７＝０．３０となる電池Ｄとした。
【００４５】
（比較例２）
極板群の最外周部分である幅６０ｍｍのセパレータ３には何も上端部絶縁部材１１ａおよび下端部絶縁部材１１ｂを貼着せず、熱溶着により群の形状を保持させたこと以外は実施例１と同様にして円筒型リチウムイオン二次電池を作製し、電池Ｅとした。
【００４６】
（比較例３）
正極板最外周の正極集電体１ａの上端面を被覆するように上端部絶縁部材１１ａを上端部より下方に４．５ｍｍ、上方に１．５ｍｍの位置に対向するように幅６．０ｍｍの絶縁テープをセパレータ３の最外周の外側に貼着して配設したが、正極板最外周の正極集電体１ａの下端面には何も下端部絶縁部材１１ｂを貼着しなかった以外は実施例１と同様にして円筒型リチウムイオン二次電池を作製し、Ｓ／Ｍ＝（４．５＋０）／５７＝０．０８となる電池Ｆとした。
【００４７】
（比較例４）
正極板最外周の正極集電体１ａの下端面を被覆するように下端部絶縁部材１１ｂを下端部より上方に５．４ｍｍ、下方に１．６ｍｍの位置に対向するように幅７．０ｍｍの絶縁テープをセパレータ３の最外周の内側に貼着して配設したが、正極板最外周の正極集電体１ａの上端面には何も上端部絶縁部材１１ａを貼着しなかった以外は実施例１と同様にして円筒型リチウムイオン二次電池を作製し、Ｓ／Ｍ＝（０＋５．４）／５７＝０．０９となる電池Ｇとした。
【００４８】
（比較例５）
正極板最外周の正極集電体１ａの上面を被覆するように上端部絶縁部材１１ａを上端部より下方に２．０ｍｍの位置から下方に４．５ｍｍ、上方に３．５ｍｍの位置に対向するように幅８ｍｍの絶縁テープをセパレータ３の最外周の外側に貼着して配設し、正極板最外周の正極集電体１ａの下面を被覆するように下端部絶縁部材１１ｂを下端部より上方に２．０ｍｍの位置から上方に４．５ｍｍ、下方に３．５ｍｍの位置に対向するように幅８ｍｍの絶縁テープをセパレータ３の最外周の外側に貼着して配設した以外は実施例１と同様にして円筒型リチウムイオン二次電池を作製し、Ｓ／Ｍ＝（４．５＋４．５）／５７＝０．１６となる電池Ｈとした。
【００４９】
このようにして得られた実施例１〜実施例３、比較例１〜比較例５の各電池５個について、充放電サイクル特性を評価した。充放電サイクル特性は、４．２Ｖで２時間の定電流−定電圧充電を行い、電池電圧が４．２Ｖに達するまでは１４００ｍＡ（０．７ＩｔＡ）の定電流充電を行い、その後、電流値が減衰して１００ｍＡ（０．０５ＩｔＡ）になるまで充電した後、２０００ｍＡ（１ＩｔＡ）の定電流で３．０Ｖの放電終止電圧まで放電する充放電サイクル試験を２０℃の環境下で繰り返し、３サイクル目を初期容量とし、この充放電サイクルを５００サイクル繰り返した時点の初期容量に対する容量維持率の平均値の結果を表１に示す。
【００５０】
また充放電サイクルを５００サイクル繰り返した時点で、各電池を分解して電池Ａ〜電池Ｈの負極板Ａ〜負極板Ｈを取りだして、図３に示すように負極板を均等に５分割してそれぞれの部位において、厚みを測定し、極板厚み比＝（選択部分の厚み）／（中央部（▲３▼）の厚み）として比率を求めるとともに、目視にて極板観察を行い、負極板の亀裂の有無を観察した結果を表１に示す。
【００５１】
なお、それぞれの部位の厚みは５点、厚みゲージで測定した場合の平均値を用いた。
【００５２】
【表１】

【００５３】
本発明の非水電解液二次電池は比較例の電池と比べて、充放電サイクルを繰り返しても電池容量の劣化が少なく充放電サイクル特性に優れ、負極板に亀裂が入ることがなく、信頼性の高い電池であることがわかった。正極板の最外周は、正極合剤層が無く正極集電体１ａのみで、充放電サイクル時の発熱を電池ケース４を通じて外部に放出させることができ、極板群の膨張、収縮を抑制することができる上、極板群を上下端部で固定することで、充放電時の膨張・収縮を極板内部で均一に緩和することができるためであると推定できる。
【００５４】
【発明の効果】
以上の説明から明らかのように、本発明によれば、極板群の最外周に絶縁部材を配設する位置と幅を最適化することにより、充放電サイクルを繰り返しても電池容量の劣化の少ない電池を得ることができる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る主要構成を示す電池断面図
【図２】（ａ）本発明の極板群上端部の一部縦断面図
（ｂ）本発明の極板群下端部の一部縦断面図
（ｃ）本発明の別の極板群上端部の一部縦断面図
（ｄ）本発明の別の極板群下端部の一部縦断面図
【図３】負極板の分割図
【符号の説明】
１正極板
１ａ正極集電体
２負極板
２ａ負極集電体
３セパレータ
４電池ケース
５封口板
６ガスケット
７正極リード
８負極リード
９上部絶縁板
１０下部絶縁板
１１ａ上端部絶縁部材
１１ｂ下端部絶縁部材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery excellent in battery characteristics after storage at high temperature and charge / discharge cycle characteristics.
[0002]
[Prior art]
Conventionally, nickel cadmium storage batteries and nickel metal hydride storage batteries have been mainly used as driving power sources for AV equipment, notebook computers, portable communication equipment, etc., but in recent years, electronic devices have become more portable and cordless. As it has become established, the demand for higher energy density and smaller size and weight of the secondary battery as the driving power source has become stronger. Non-aqueous electrolyte secondary batteries typified by lithium ion secondary batteries, which have extremely remarkable characteristics of being capable of rapid charging while having a small size and light weight and having a high energy density as a battery that meets such demands. Developed and mainstream.
[0003]
As shown in FIG. 1, the non-aqueous electrolyte secondary battery includes a positive electrode plate in which a positive electrode mixture layer using a lithium-containing transition metal compound, for example, LiCoO ₂ as a positive electrode active material is formed on an aluminum positive electrode current collector 1a. 1 and a negative electrode plate 2 formed by winding a negative electrode plate 2 in which a negative electrode mixture layer having a carbon material as a negative electrode active material is formed on a copper negative electrode current collector with a separator 3 interposed therebetween, non-aqueous electrolysis The battery and the electrode plate group and the non-aqueous electrolyte are stored in a battery case 4 and use lithium ion insertion and detachment to suppress expansion and contraction during the charge / discharge cycle, and charge / discharge cycle characteristics. As a method of improving, a method of thermally welding and fixing a separator (for example, refer to Patent Document 1) and a method of attaching an insulating member at the outermost peripheral part have been proposed (for example, refer to Patent Documents 2 to 4). ).
[0004]
However, with higher functionality of electronic devices, there is a strong demand for higher capacities and higher energy densities. Thinning separators and current collectors that do not contribute to capacity, and increasing the packing density of electrode plates Therefore, heat generation during the charge / discharge cycle is increased, and it is difficult to suppress expansion and contraction of the electrode plate group.
[0005]
[Patent Document 1]
JP 2001-167799 A [Patent Document 2]
Japanese Patent Laid-Open No. 10-247503 [Patent Document 3]
JP 2000-251866 A [Patent Document 4]
JP-A-2002-124293 [0006]
[Problems to be solved by the invention]
The present invention has been made in view of such a problem, and suppresses the expansion and contraction of the electrode plate group due to heat generation during the charge / discharge cycle, has excellent charge / discharge cycle characteristics, and is a highly reliable non-aqueous electrolyte secondary solution. The main purpose is to provide a battery.
[0007]
[Means for Solving the Problems]
The present invention for solving the above-mentioned problems includes an electrode plate group formed by winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween, a non-aqueous electrolyte, and the electrode plate group and the non-aqueous solution. In a non-aqueous electrolyte secondary battery comprising a battery case containing an electrolyte solution, a positive current collector is provided in a region where the positive electrode current collector is opposed to the positive electrode current collector layer without a positive electrode mixture layer of the positive electrode plate. body and the insulating member on the separator at a position opposing are disposed on upper and lower ends, when the width of the cathode current collector and the opposite to that insulating member S, the positive electrode plate width is M (S /M)≦0.20 .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a battery cross-sectional view showing the main configuration of a cylindrical lithium secondary battery, and FIGS. 2A and 2B are partial vertical cross-sectional views thereof. A battery plate 4 and a non-aqueous electrolyte solution (not shown) formed by winding the positive electrode plate 1 and the negative electrode plate 2 with the separator 3 interposed therebetween are housed in the battery case 4. The positive electrode plate 1 has a positive electrode active material, a binder, a conductive agent, and a thickener as needed as a solvent on one or both sides of a positive electrode current collector 1a made of an aluminum foil, a lath-processed or etched foil, or the like. It is possible to form a positive electrode mixture layer by applying, drying and rolling a paste-like positive electrode mixture kneaded and dispersed in the material, and the thickness is preferably 100 μm to 200 μm and preferably flexible.
[0009]
The outermost periphery of the positive electrode plate has no positive electrode mixture layer and is only the positive electrode current collector 1 a, and heat generated during the charge / discharge cycle can be released to the outside through the battery case 4.
[0010]
As the positive electrode active material, for example, a lithium-containing transition metal compound that can accept lithium ions as a guest is used. For example, a composite metal oxide of at least one metal selected from cobalt, manganese, nickel, chromium, iron, and vanadium and lithium, LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiCo _x Ni _(1-x) O ₂ ( 0 <x <1), LiCrO ₂ , αLiFeO ₂ , LiVO _{2 and the} like are preferable.
[0011]
The binder is not particularly limited as long as it is a material that is stable with respect to the solvent or electrolyte used, but for example, a fluorine-based binder, acrylic rubber, modified acrylic rubber, styrene-butadiene rubber (SBR), Isopropylene rubber, butadiene rubber, acrylic polymer, vinyl polymer and the like can be used alone or as a mixture or copolymer of two or more kinds. Examples of the fluorine-based binder include polyvinylidene fluoride (PVDF), a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P (VDF-HFP)), and a polytetrafluoroethylene resin disperser. John and the like are preferable.
[0012]
As the thickener, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, casein and the like are preferable.
[0013]
As the conductive agent, acetylene black, furnace black, graphite, graphite, carbon fiber, or the like is used alone or as a mixture of two or more.
[0014]
As the solvent, a solvent capable of dissolving the binder is suitable, and in the case of an organic binder, N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide, tetrahydrofuran, dimethylacetamide, dimethylsulfoxide. In addition, an organic solvent such as hexamethylsulfuramide, tetramethylurea, acetone, methylethylketone or the like is preferably used alone or a mixed solvent thereof. In the case of an aqueous binder, water or warm water is preferable. In addition, the negative electrode plate 2 is coated with a paste-like negative electrode mixture in which a negative electrode active material and a binder, and if necessary, a thickener and a conductive additive are kneaded and dispersed in a solvent, on one side or both sides of the negative electrode current collector. The negative electrode mixture layer can be formed by drying and rolling, and the thickness is preferably 100 μm to 210 μm and preferably flexible.
[0015]
Although it does not specifically limit as a negative electrode active material, For example, it obtains by baking the carbon material obtained by baking organic polymer compounds (Phenol resin, polyacrylonitrile, cellulose, etc.), coke, and pitch. The carbon material to be used, or artificial graphite, natural graphite or the like is preferable. As the shape thereof, a spherical shape, a scale shape or a lump shape can be used.
[0016]
The copper or copper alloy used as the negative electrode current collector is not particularly limited, and examples thereof include rolled foil, electrolytic foil, and the shape thereof may be foil, perforated foil, expanded material, lath material, and the like. Although the thickness is preferably as the tensile strength is strong, the thickness is preferably 20 μm or less, more preferably in the range of 8 to 15 μm because the void volume inside the battery decreases and the energy density decreases as the thickness increases.
[0017]
As the binder, the solvent, and the conductive auxiliary agent that can be added as necessary, the same conductive agent as that of the positive electrode can be used.
[0018]
By the way, the method of preparing a paste mixture by kneading and dispersing a positive electrode and negative electrode active material, a binder, a conductive agent to be added as necessary, and a conductive auxiliary in a solvent is not particularly limited. A planetary mixer, a homomixer, a pin mixer, a kneader, a homogenizer, or the like can be used. These can be used alone or in combination.
[0019]
In addition, various dispersants, surfactants, stabilizers, and the like can be added as needed during the kneading and dispersing of the paste mixture.
[0020]
The coating and drying is not particularly limited, and the paste-like mixture kneaded and dispersed as described above, for example, slit die coater, reverse roll coater, lip coater, blade coater, knife coater, gravure coater. It can be applied easily using a dip coater or the like, and drying close to natural drying is preferred, but drying is preferably performed at a temperature of 70 ° C. to 200 ° C. in consideration of productivity.
[0021]
Rolling is preferably performed several times at a linear pressure of 1000 to 2000 kg / cm or by changing the linear pressure until a predetermined thickness is reached by a roll press.
[0022]
The separator is composed of a single-layer or multi-layer structure made of a polyolefin resin microporous film such as polyethylene resin or polypropylene resin, or a non-woven fabric. Two or both layers of polyethylene resin and polypropylene resin are polypropylene resin and the intermediate layer is polyethylene. A separator having a shutdown function with a three-layer structure of resin is preferable, and the thickness of the separator is preferably in the range of 10 to 30 μm.
[0023]
The insulating member is composed of a base material and a paste, and the thickness of the base material is preferably in the range of 20 μm to 60 μm, and the thickness of the paste is preferably in the range of 20 μm to 80 μm from the viewpoints of insulation, sticking properties, and workability. .
[0024]
Examples of the material of the insulating member base material include polyolefin resins such as polyethylene resin and polypropylene resin, polyethylene terephthalate resin, polyether ether ketone resin, polyphenylene sulfide resin, polyarylate resin, polyamide resin, polyimide resin, and fluorine resin. A resin obtained by singly or blending them, or a modified resin can be used. And you may add fillers, such as glass fiber, a talc, and a silica.
[0025]
Examples of the paste for the insulating member include natural rubber, isobutyl rubber, styrene butadiene rubber, silicon rubber, urethane rubber, and acrylic resin. These can be used alone, laminated or modified.
[0026]
An upper end insulating member 11a and a lower end insulating member 11b are arranged on the outermost periphery of the electrode plate group obtained by winding the positive electrode plate 1 and the negative electrode plate 2 obtained in this manner with the separator 3 interposed therebetween. In the battery case 4. At this time, the position and width at which the upper end insulating member 11a and the lower end insulating member 11b are disposed are important, and the positive electrode current collector 1a and the battery case 4 are not separated from the positive electrode plate 1 without the positive electrode mixture layer. The upper end insulating member 11a and the lower end insulating member 11b are disposed on the separator 3 at positions facing the upper and lower ends of the positive electrode current collector 1a in the region facing each other through the positive electrode current collector 1a. When the sum of the widths of the opposing upper end insulating member 11a and lower end insulating member 11b is S and the positive electrode plate width is M (S / M) ≦ 0.20.
[0027]
The outermost periphery of the positive electrode plate 1 has no positive electrode mixture layer and is only the positive electrode current collector 1a. Heat generated during the charge / discharge cycle can be released to the outside through the battery case 4, and the insulating member is used as the outermost separator. By sticking, the expansion and contraction of the electrode plate group can be suppressed, but in order to avoid the risk of short-circuiting with the battery case 4 due to burrs at the upper and lower ends of the positive electrode current collector 1a, insulation is performed. It is necessary to arrange a member in this part.
[0028]
Further, the ratio of (S / M) is preferably 0.20 or less, and the range of 0.05 or more and 0.20 or less is optimal. If it exceeds 0.20, the effect of suppressing expansion and contraction at the time of charging / discharging is not changed, and it is not preferable because it hinders charging / discharging. It is not preferable because there is almost no effect of suppressing shrinkage.
[0029]
By the way, the outermost periphery of the positive electrode plate 1 has only the positive electrode current collector 1a without the positive electrode mixture layer, and further, the outermost periphery of the negative electrode plate 2 has the negative electrode mixture layer as shown in FIGS. By using only the negative electrode current collector 2a, heat generation during the charge / discharge cycle can be more efficiently discharged to the outside through the battery case 4.
[0030]
The non-aqueous electrolyte is composed of a non-aqueous solvent and an electrolyte, and the non-aqueous solvent contains a cyclic carbonate and a chain carbonate as main components. The cyclic carbonate is preferably at least one selected from ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). The chain carbonate is preferably at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and the like.
[0031]
As the electrolyte, for example, a lithium salt having a strong electron-withdrawing property is used. For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C) ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) _{3 and the} like. These electrolytes may be used alone or in combination of two or more. These electrolytes are preferably dissolved at a concentration of 0.5 to 1.5 M in the non-aqueous solvent.
[0032]
【Example】
Hereinafter, although it demonstrates in detail using an Example and a comparative example, these do not limit this invention at all.
[0033]
Example 1
The positive electrode plate 1 has 100 parts by weight of lithium cobaltate as a positive electrode active material, 3 parts by weight of acetylene black carbon powder as a conductive agent, and 4% by weight of polytetrafluoroethylene (PTFE) resin dispersion as a binder. As a thickener, 0.8 parts by weight of a carboxymethyl cellulose aqueous solution as a thickener was kneaded and dispersed to prepare a paste mixture. The paste mixture is continuously applied intermittently to a positive electrode current collector 1a made of a strip-shaped aluminum foil having a thickness of 20 μm and dried to produce a positive electrode plate 1 having a thickness of 290 μm, and a linear pressure of 1000 kg / cm The thickness of the positive electrode plate was rolled to 180 μm. The positive electrode lead 7 was spot welded and attached to a portion where the positive electrode current collector layer 1a was not exposed on the outermost periphery of the positive electrode plate 1 and then the positive electrode plate was dried at 120 ° C. for 15 minutes. .
[0034]
Next, the negative electrode plate has 100 parts by weight of scaly graphite capable of occluding and releasing lithium foil as a negative electrode active material, 4 parts by weight of a water-soluble dispersion of styrene butadiene rubber (SBR) as a binder, and thickened. As an agent, 0.8 parts by weight of a carboxymethyl cellulose aqueous solution was kneaded and dispersed to prepare a paste-like mixture. This paste-like mixture is continuously applied intermittently to a negative electrode current collector made of a strip-shaped copper foil having a thickness of 14 μm and dried to produce a negative electrode plate 2 having a thickness of 300 μm, and a linear pressure of 110 kg / cm. The negative electrode plate was rolled to 196 μm by rolling three times. The negative electrode plate 3 was spot welded to the portion where the negative electrode mixture layer was not present in the innermost periphery of the negative electrode plate 3 and the negative electrode current collector was exposed, and the negative electrode lead 8 was attached. Then, the negative electrode plate was dried at 110 ° C. for 10 minutes. .
[0035]
A positive electrode plate 1 and a negative electrode plate 2 obtained in this manner were wound in a state where the heat-resistant temperature was 138 ° C. and insulated via a polypropylene separator 3 having a thickness of 20 μm.
[0036]
As shown in FIG. 2A of this electrode plate group, the upper end insulating member 11a is 4.0 mm below the upper end so as to cover the upper end surface of the positive electrode current collector 1a on the outermost periphery of the 57 mm wide positive electrode plate. Then, an insulating tape having a width of 6 mm was attached to the outside of the outermost periphery of the separator 3 having a width of 60 mm so as to face the position of 2.0 mm above.
[0037]
Next, as shown in FIG. 2B, the lower end insulating member 11b is 4.0 mm above the lower end and 2. mm below the lower end so as to cover the lower end surface of the positive electrode current collector 1a on the outermost periphery of the positive electrode plate. An insulating tape having a width of 6 mm was attached to the outside of the outermost periphery of the separator 3 so as to face the position of 0 mm.
[0038]
At this time, S / M = (4.0 + 4.0) /57=0.14.
[0039]
The upper end insulating member 11a and the lower end insulating member 11b are made of an insulating tape made of a 40 μm thick polypropylene resin base material and a 10 μm thick urethane resin paste so that no gap is generated. I let you.
[0040]
Next, the negative electrode lead 9 connected to the negative electrode plate 6 is electrically connected to the case 8 via the lower insulating plate 10, and the positive electrode lead 3 connected to the positive electrode plate 5 is sealed via the upper insulating plate 4. After electrically connecting to the internal terminals of the plate 1, a non-aqueous electrolyte (not shown) is injected, the sealing plate 5 and the battery case 4 are caulked and sealed via the insulating gasket 6, and the diameter is 18 mm. A cylindrical lithium ion secondary battery having a size of 65 mm and a battery capacity of 2000 mAh was produced and designated as battery A.
[0041]
The electrolytic solution was an electrolytic solution in which 1.0 mol of lithium hexafluorophosphate (LiPF ₆ ) was dissolved as an electrolyte in a mixed solvent of 30% by volume of ethylene carbonate, 50% by volume of ethyl methyl carbonate, and 20% by volume of methyl propionate. Was injected in a predetermined amount. This electrolytic solution is impregnated in the positive electrode active material layer and the negative electrode active material layer, and is responsible for the movement of Li ions between the positive electrode plate 1 and the negative electrode plate 2 through the separator of the microporous membrane in the battery reaction.
[0042]
(Example 2)
The upper end insulating member 11a has a width of 7.5 mm so as to face the position of 6.0 mm below the upper end and 1.5 mm above the upper end so as to cover the upper end surface of the positive electrode current collector 1a on the outermost periphery of the positive electrode plate. 4. An insulating tape is attached to the outside of the outermost periphery of the separator 3, and the lower end insulating member 11b is placed above the lower end so as to cover the lower end surface of the positive electrode current collector 1a on the outermost periphery of the positive electrode plate. Cylindrical lithium ion in the same manner as in Example 1 except that an insulating tape having a width of 7.0 mm was attached to the outside of the outermost periphery of the separator 3 so as to face the position of 4 mm and 1.6 mm below. A secondary battery was produced, and battery B was obtained such that S / M = (6.0 + 5.4) /57=0.20.
[0043]
(Example 3)
The upper end insulating member 11a has a width of 2.5 mm so as to face the position of 1.3 mm below the upper end and 1.2 mm above the upper end so as to cover the upper end surface of the positive electrode current collector 1a on the outermost periphery of the positive electrode plate. An insulating tape is attached to the outside of the outermost periphery of the separator 3, and the lower end insulating member 11b is disposed above the lower end so as to cover the lower end surface of the positive electrode current collector 1a on the outermost periphery of the positive electrode plate. Cylindrical lithium ions in the same manner as in Example 1 except that an insulating tape having a width of 3.0 mm was attached to the outermost outer periphery of the separator 3 so as to face the position of 5 mm and 1.5 mm below. A secondary battery was produced, and battery C was obtained such that S / M = (1.3 + 1.5) /57=0.05.
[0044]
(Comparative Example 1)
An insulating tape having a width of 10 mm so that the upper end insulating member 11a faces the position of 8.5 mm below the upper end and 1.5 mm above the upper end so as to cover the upper end surface of the positive electrode current collector 1a on the outermost periphery of the positive electrode plate Is attached to the outside of the outermost periphery of the separator 3, and the lower end insulating member 11b is 8.5 mm above the lower end so as to cover the lower end surface of the positive electrode current collector 1a on the outermost periphery of the positive electrode plate. A cylindrical lithium ion secondary battery was prepared in the same manner as in Example 1 except that an insulating tape having a width of 10 mm was attached to the outside of the outermost periphery of the separator 3 so as to face the position of 1.5 mm below. The battery D was produced, and S / M = (8.5 + 8.5) /57=0.30.
[0045]
(Comparative Example 2)
Example 1 except that the upper end insulating member 11a and the lower end insulating member 11b are not attached to the separator 3 having a width of 60 mm, which is the outermost peripheral portion of the electrode plate group, and the shape of the group is maintained by thermal welding. In the same manner as above, a cylindrical lithium ion secondary battery was produced and designated as battery E.
[0046]
(Comparative Example 3)
The upper end insulating member 11a has a width of 6.0 mm so as to face the position of 4.5 mm below the upper end and 1.5 mm above the upper end so as to cover the upper end surface of the positive electrode current collector 1a on the outermost periphery of the positive electrode plate. Insulating tape was disposed on the outer periphery of the outermost periphery of the separator 3 except that the lower end insulating member 11b was not adhered to the lower end surface of the positive electrode current collector 1a on the outermost periphery of the positive electrode plate. A cylindrical lithium ion secondary battery was produced in the same manner as in Example 1, and a battery F in which S / M = (4.5 + 0) /57=0.08 was obtained.
[0047]
(Comparative Example 4)
The lower end insulating member 11b has a width of 7.0 mm so as to face the position of 5.4 mm above the lower end and 1.6 mm below so as to cover the lower end surface of the positive electrode current collector 1a on the outermost periphery of the positive electrode plate. Insulating tape was disposed by being adhered to the inside of the outermost periphery of the separator 3, except that no upper end insulating member 11a was adhered to the upper end surface of the positive electrode current collector 1a on the outermost periphery of the positive electrode plate. A cylindrical lithium ion secondary battery was produced in the same manner as in Example 1, and a battery G satisfying S / M = (0 + 5.4) /57=0.09 was obtained.
[0048]
(Comparative Example 5)
The upper end insulating member 11a is opposed to a position 4.5mm downward from a position 2.0mm below the upper end and 3.5mm upward so as to cover the upper surface of the positive electrode current collector 1a on the outermost periphery of the positive electrode plate. In this way, an insulating tape having a width of 8 mm is disposed outside the outermost periphery of the separator 3 and the lower end insulating member 11b is placed from the lower end so as to cover the lower surface of the positive electrode current collector 1a at the outermost periphery of the positive electrode plate. Implemented except that an insulating tape with a width of 8 mm was attached to the outside of the outermost periphery of the separator 3 so as to face the position of 2.0 mm upward, 4.5 mm upward, and 3.5 mm downward. A cylindrical lithium ion secondary battery was produced in the same manner as in Example 1, and a battery H in which S / M = (4.5 + 4.5) /57=0.16 was obtained.
[0049]
The charge / discharge cycle characteristics of each of the five batteries of Examples 1 to 3 and Comparative Examples 1 to 5 thus obtained were evaluated. Charging / discharging cycle characteristics are a constant current-constant voltage charge at 4.2V for 2 hours, a constant current charge of 1400mA (0.7ItA) until the battery voltage reaches 4.2V, and then the current value is After charging to 100 mA (0.05 ItA) after decaying, a charge / discharge cycle test in which a constant current of 2000 mA (1 ItA) is discharged to a discharge end voltage of 3.0 V is repeated in a 20 ° C. environment at the third cycle. Table 1 shows the results of the average value of the capacity retention ratio with respect to the initial capacity when 500 cycles of this charge / discharge cycle were repeated.
[0050]
Further, when the charge / discharge cycle is repeated 500 times, each battery is disassembled and the negative plates A to H of the batteries A to H are taken out, and the negative plate is equally divided into five as shown in FIG. At each part, the thickness is measured, and the ratio is determined as the electrode plate thickness ratio = (thickness of the selected portion) / (thickness of the central portion (3)), and the electrode plate is visually observed, and the negative electrode plate Table 1 shows the results of observation of the presence or absence of cracks.
[0051]
The thickness of each part was 5 points, and the average value when measured with a thickness gauge was used.
[0052]
[Table 1]

[0053]
The non-aqueous electrolyte secondary battery of the present invention is superior to the battery of the comparative example in that the capacity of the battery is less deteriorated even when the charge / discharge cycle is repeated, and the negative electrode plate is not cracked and reliable. It turned out to be a battery with high performance. The outermost periphery of the positive electrode plate has no positive electrode mixture layer and is only the positive electrode current collector 1a, and heat generated during the charge / discharge cycle can be released to the outside through the battery case 4, thereby suppressing expansion and contraction of the electrode plate group. In addition, it can be estimated that the expansion and contraction during charging / discharging can be uniformly relieved inside the electrode plate by fixing the electrode plate group at the upper and lower ends.
[0054]
【The invention's effect】
As is clear from the above description, according to the present invention, by optimizing the position and width at which the insulating member is disposed on the outermost periphery of the electrode plate group, the battery capacity is not deteriorated even if the charge / discharge cycle is repeated. Fewer batteries can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a battery showing a main configuration according to an embodiment of the present invention. FIG. 2 (a) is a partial vertical cross-sectional view of the upper end portion of the electrode plate group of the present invention. (C) Partial vertical sectional view of the upper end of another electrode group of the present invention (d) Partial vertical sectional view of the lower end of another electrode group of the present invention [FIG. 3] Negative electrode Board division [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Positive electrode plate 1a Positive electrode collector 2 Negative electrode plate 2a Negative electrode collector 3 Separator 4 Battery case 5 Sealing plate 6 Gasket 7 Positive electrode lead 8 Negative electrode lead 9 Upper insulating plate 10 Lower insulating plate 11a Upper end insulating member 11b Lower end insulating member

Claims

Non-aqueous electrolyte comprising electrode plate group formed by winding positive electrode plate and negative electrode plate with separator interposed therebetween, non-aqueous electrolyte, and battery case housing said electrode plate group and non-aqueous electrolyte solution In the secondary battery, in the region where the battery case and the positive electrode mixture layer of the positive electrode plate are not provided and the positive electrode current collector is opposed via the separator, the battery case and the positive electrode current collector are positioned on the separator at positions facing the upper and lower ends. the insulating member is disposed, the width of the positive electrode current collector and the opposite to that insulating member S, when the positive electrode plate width is M, the (S / M) ≦ 0.20 der Rukoto Non-aqueous electrolyte secondary battery characterized.

The non-aqueous electrolyte secondary battery according to claim 1, wherein the battery case is a cylindrical battery case.