JP4712139B2 - Lithium secondary battery - Google Patents
Lithium secondary battery Download PDFInfo
- Publication number
- JP4712139B2 JP4712139B2 JP30486198A JP30486198A JP4712139B2 JP 4712139 B2 JP4712139 B2 JP 4712139B2 JP 30486198 A JP30486198 A JP 30486198A JP 30486198 A JP30486198 A JP 30486198A JP 4712139 B2 JP4712139 B2 JP 4712139B2
- Authority
- JP
- Japan
- Prior art keywords
- battery
- separator
- reference example
- positive
- negative electrode
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Landscapes
- Cell Separators (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Description
【0001】
【発明の属する技術分野】
本発明は、リチウム二次電池の正、負極間の電解液保持および電解液の拡散に関するものである。
【0002】
【従来の技術】
近年、パソコンおよび携帯電話等の電子機器の小型軽量化、コードレス化が急速に進んでおり、これらの駆動用電源として、高エネルギー密度を有する二次電池が要求されている。この中でリチウムを活物質とするリチウム二次電池はとりわけ高電圧、高エネルギー密度を有する電池として期待が大きい。従来、この電池には負極に金属リチウム、正極に二硫化モリブデン、二酸化マンガン、五酸化バナジウムなどが用いられ、3V級の電池が実現されていた。
【0003】
ところが、負極に金属リチウムを用いた場合、充電時に樹枝状(デンドライト状)リチウムの析出が起こり、充放電の繰り返しとともに極板上に堆積した樹枝状リチウムが、極板から分離して電解液中を浮遊し、正極と接触して微少短絡を起こし、充放電効率が100%未満となり、サイクル寿命が短くなるという問題があった。また、樹枝状リチウムは表面積が大きく、反応性が高いため、安全性の点でも問題があった。
【0004】
そこで、最近は金属リチウムの代わりに、負極に炭素材を用い、正極にリチウム含有酸化物を用いたリチウムイオン二次電池が研究の中心となり、一部商品化されている。この電池では負極においてリチウムは炭素中にイオンとして吸蔵された状態で存在するため、従来の金属リチウム系と比べ非常に安全であるとされている。
【0005】
【発明が解決しようとする課題】
しかし、リチウムイオン二次電池系の正極に用いるリチウム含有酸化物はリチウムに対し4Vという高電位を有するため、従来の3V級リチウム二次電池に比べ、電解液中の有機溶媒が酸化分解されやすく、充放電に伴って電解液が枯渇し、一方負極に用いる炭素、特に黒鉛は電解液との反応性が高く、ここでも電解液の枯渇が起こりやすい。また、この電解液の枯渇は温度の上がりやすい正、負極の短い方向の中央部から起こる。このような極板上の部分的な電解液の枯渇が充放電サイクル寿命の低下を招く恐れがある。
【0006】
そこで、正、負極の短い方向の中央部に電解液の拡散が容易であれば上記のような極板上の部分的な電解液の枯渇は起こりにくいが、リチウムイオン二次電池の構造は例えば円筒型では図1に示すように、セパレータ1を介して帯状正極板2と負極板3を複数回渦巻状に密に巻回しており、また非水電解液はある程度の粘性があることから電解液の拡散は非常に起こりにくい。
【0007】
このような欠点に対して、セパレータに溝を付けて電解液を電極群内部に浸透させる方法が特開平6-333550等で報告されている。しかし、電極群は構成時に高いテンションをかけて巻くため、セパレータに溝を入れた場合溝の入った部分は薄くなるため、強度が弱くなりその部分の伸び率が変わるもしくはひどい場合破断する可能性がある。
【0008】
本発明は、上記の課題を解決するものであり、正、負極間の電解液量を増大させて電解液の枯渇を防止し、また電極群中の電解液の拡散を容易にすることにより極板上の部分的な電解液の枯渇を抑制し、充放電サイクル寿命特性に優れたリチウム二次電池を提供することを目的とする。
【0009】
【発明の実施の形態】
本発明は、少なくともいずれか一方の面にポリオレフィン粒子もしくはポリオレフィン繊維を固定し表面粗度が5μm以上10μm以下である正、負極を用いるものである。さらに、固定するポリオレフィン粒子もしくはポリオレフィン繊維はポリエチレン、ポリプロピレン製がより好ましい。
【0010】
このような構成をすることにより、セパレータの強度を維持した状態で正、負極間にできる間隙の部分に電解液を多く保持することができ、電解液と正、負極のガス発生もしくは被膜形成等の不可逆反応による電解液の枯渇を抑えることができる。また、正、負極間における電解液の拡散がこの間隙を通ることにより容易になり、極板上での部分的な電解液の枯渇も抑制されるため優れた充放電サイクル寿命特性を有する電池を提供することができる。
【0011】
【実施例】
以下、本発明の実施例を図面を参照しながら説明する。
【0012】
図1に本実施例で用いた円筒型リチウムイオン二次電池(直径17mm、総高50mm)の縦断面図を示す。この図より明らかなように、セパレータ1を介して、帯状正極板2と負極板3を複数回渦巻状に巻回して、電極群が構成される。正極板2と負極板3にはそれぞれアルミニウム製正極リード片4およびニッケル製負極リード片5を溶接している。電極群の上下面に突出したセパレータ1を加熱収縮させた後にポリエチレン製底部絶縁板6を装着し、ニッケルメッキ鉄製電池ケース7内に収容し、負極リード片5の他端を電池ケース7の内定面にスポット溶接する。電極群上面にポリエチレン製上部絶縁板8を載置してから電池ケース7の開口部の所定位置に溝入れし、所定量の非水電解液を注入含浸させる。ポリプロピレン製ガスケット9を周縁部に装着させたステンレス鋼製の封口板10の下面に正極リード片4の他端をスポット溶接した後、電池ケース7の開口部にガスケット9を介して封口板10を装着し、電池ケース7の上縁部を内方にカールさせて密封口し、電池が完成する。
【0013】
(参考例1)
正極はLi2CO3とCo3O4とを混合し、900℃で10時間焼成して合成したLiCoO2100重量部に導電材としてアセチレンブラック3重量部、結着剤としてポリ四フッ化エチレン7重量部を混合し、LiCoO2に対し1%カルボキシメチルセルロース水溶液100重量部に加え、撹拌混合し正極合剤ペーストとした。集電体厚さが30μmのアルミニウム箔の両面に正極合剤ペーストを塗布し、乾燥後圧延ローラーを用いて圧延を行い、所定寸法に裁断して正極板とした。
【0014】
また、負極は以下のように作製した。まず、平均粒径が約20μmになるように粉砕、分級した鱗片状黒鉛と結着剤のスチレン/ブタジエンゴム3重量部を混合した後、黒鉛に対し1%カルボキシメチルセルロース水溶液100重量部に加え、撹拌混合し負極ペーストとした。集電体厚さが20μmの銅箔の両面に負極合剤ペーストを塗布し、乾燥後圧延ローラーを用いて行い、所定寸法に裁断して負極板とした。
【0015】
セパレータとしては、厚みが20μmのポリエチレン製セパレータの片面にポリエチレン粒子を固定し、表面粗度が0.1μmとしたものを用いた。そして、このセパレータの粗面部を正極と対向するように電極群を構成した。
【0016】
なお、非水電解液にはエチレンカーボネートとエチルメチルカーボネートとを1:3の体積比で混合した溶媒に1.5モル/リットルのLiPF6を溶解したものを用い、これを注液した後密封口した。これを電池Aとした。
【0017】
(参考例2)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン粒子を固定し、表面粗度が1.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Bとした。
【0018】
(参考例3)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン粒子を固定し、表面粗度が5.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Cとした。
【0019】
(参考例4)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン粒子を固定し 、表面粗度が10.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Dとした。
【0020】
(参考例5)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン粒子を固定し、表面粗度が20.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Eとした。
【0021】
(参考例6)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン粒子を固定し、表面粗度が30.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Fとした。
【0022】
(参考例7)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン繊維を正、負極の短い方向に対し0°に配置されるように固定し、表面粗度が0.1μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Gとした。
【0023】
(参考例8)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン繊維を正、負極の短い方向に対し0°に配置されるように固定し、表面粗度が1.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Hとした。
【0024】
(参考例9)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン繊維を正、負極の短い方向に対し0°に配置されるように固定し、表面粗度が5.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Iとした。
【0025】
(参考例10)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン繊維を正、負極の短い方向に対し0°に配置されるように固定し、表面粗度が10.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Jとした。
【0026】
(参考例11)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン繊維を正、負極の短い方向に対し0°に配置されるように固定し、表面粗度が20.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Kとした。
【0027】
(参考例12)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン繊維を正、負極の短い方向に対し0°に配置されるように固定し、表面粗度が30.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Lとした。
【0028】
(参考例13)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン繊維を正、負極の短い方向に対し90°に配置されるように固定し、表面粗度が5.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Mとした。
【0029】
(参考例14)
負極は(参考例1)で作製したものの片面にポリエチレン繊維を正、負極の短い方向に対し0°に配置されるように固定し、表面粗度が0.1μmとしたものを用いた。セパレータは、厚みが20μmのポリエチレン製の表面処理を施していないものを用いた。上記以外は(参考例1)と同様の電池を作製した。これを電池Nとした。
【0030】
(参考例15)
負極は(参考例1)で作製したものの片面にポリエチレン繊維を正、負極の短い方向に対し0°に配置されるように固定し、表面粗度が1.0μmとしたものを用いた以外は(参考例14)と同様の電池を作製した。これを電池Oとした。
【0031】
(実施例1)
負極は(参考例1)で作製したものの片面にポリエチレン繊維を正、負極の短い方向に対し0°に配置されるように固定し、表面粗度が5.0μmとしたものを用いた以外は(参考例14)と同様の電池を作製した。これを電池Pとした。
【0032】
(実施例2)
負極は(参考例1)で作製したものの片面にポリエチレン繊維を正、負極の短い方向に対し0°に配置されるように固定し、表面粗度が10.0μmとしたものを用いた以外は(参考例14)と同様の電池を作製した。これを電池Qとした。
【0033】
(参考例16)
負極は(参考例1)で作製したものの片面にポリエチレン繊維を正、負極の短い方向に対し0°に配置されるように固定し、表面粗度が20.0μmとしたものを用いた以外は(参考例14)と同様の電池を作製した。これを電池Rとした。
【0034】
(参考例17)
負極は(参考例1)で作製したものの片面にポリエチレン繊維を正、負極の短い方向に対し0°に配置されるように固定し、表面粗度が30.0μmとしたものを用いた以外は(参考例14)と同様の電池を作製した。これを電池Sとした。
【0035】
(実施例3)
負極は(参考例1)で作製したものの片面にポリエチレン繊維を正、負極の短い方向に対し90°に配置されるように固定し、表面粗度が5.0μmとしたものを用いた以外は(参考例14)と同様の電池を作製した。これを電池Tとした。
【0036】
(比較例1)
厚みが20μmのポリエチレン製の表面処理を施していないセパレータ、および表面処理を施していない正、負極を用いた以外は(参考例1)と同様の電池を作製した。これを電池Uとした。
【0037】
(参考例18)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン繊維を正、負極の短い方向に対し15°に配置されるように固定し、表面粗度が5.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Vとした。
【0038】
(参考例19)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン繊維を正、負極の短い方向に対し30°に配置されるように固定し、表面粗度が5.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Wとした。
【0039】
(参考例20)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン繊維を正、負極の短い方向に対し45°に配置されるように固定し、表面粗度が5.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Xとした。
【0040】
(参考例21)
厚みが20μmのポリエチレン製セパレータの片面にポリエチレン繊維を正、負極の短い方向に対し60°に配置されるように固定し、表面粗度が5.0μmであるセパレータを用いた以外は(参考例1)と同様の電池を作製した。これを電池Yとした。
【0041】
ここで、上記記載の表面粗度はJIS B 0601に準拠して測定される値で中心線粗さのことであり、表面粗さ測定器(SURCOM、東京精密社製)を使用し、駆動速度0.3mm/秒、測定長さ4.0mm、触針加重0.07g、カットオフ値0.8mmの条件により測定した。
【0042】
次に、電池A〜Yを各5セルずつ用意して、環境温度20℃で、上限電圧を4.2Vに設定して、最大電流560mAで2時間定電流・定電圧充電を行った。放電はこの充電状態の電池を放電電流800mA、放電終止電位3.0Vの定電流放電を行った。そして、それぞれ10サイクル目の放電容量を初期容量とし、そこで電池のレート試験を行い、2C放電維持率を算出した。
【0043】
なお、2C放電維持率は、0.2C(160mA)放電時の容量に対する2C(1600mA)放電時の容量の割合(%)とした。
【0044】
そして、初期容量の半分の容量に低下した時点のサイクル数をサイクル寿命とした。この時のサイクル寿命、2C放電維持率の5セルの平均値を(表1)に示す。
【0045】
【表1】
【0046】
(表1)の結果から、電池A〜Tは、電池Uと比べ充放電サイクル寿命が増大した。また、充放電サイクル寿命はセパレータおよび負極の表面粗度が大きくなるにつれて増大した。これは、正、負極間の間隙の部分に電解液を多く保持することができ、電解液と正、負極のガス発生もしくは皮膜形成等の不可逆反応による電解液の枯渇を抑えることができるためである。
【0047】
しかし、電池A、GおよびNでは電池Uと比べて充放電サイクル寿命があまり増大していない。つまり、この程度の表面粗度では正、負極間に保持することができる電解液量も少なく電解液の枯渇を抑制することができない。このため、充放電サイクル寿命特性を向上させるには表面粗度が少なくとも1.0μm以上必要である。
【0048】
また、電池F、LおよびSでは充放電サイクル寿命に関しては十分な特性を示しているが、2C放電維持率では他の電池と比べて著しく低下している。これは、表面粗度が大きくなるにつれて正、負極間の距離も大きくなるためである。つまり、有機溶媒はイオン伝導度が小さく、大電流放電の場合はリチウムイオンの電解液中の移動が律速となり、正、負極間の距離が大きくなりすぎると大電流放電が行いにくくなる。さらに、表面粗度が大きすぎる場合、厚みが厚くなりすぎるため電池内における正、負極の割合が減少するため、電池容量の低下を招く。また、電池容量を確保するためにセパレータの厚みを薄くすると、微多孔膜部が非常に薄くなり内部短絡等の危険性が生じる。このため、表面粗度が30μm以上ある場合は充放電サイクル寿命に関しては満足するが、大電流放電および安全性等を考慮すると表面粗度は20μm以下でなければならない。
【0049】
セパレータに繊維を固定する場合、正、負極の短い方向に対して0°に配置されている場合(電池I)の方が90°に配置されている場合(電池M)より充放電サイクル寿命が増大する。また、負極に繊維を固定する場合にも同様のことがいえる(電池PとT)。これは、電解液の酸化分解等の反応は温度が上がりやすい正、負極の短い方向の中央部から起こり始める。この時、両端部は電解液の枯渇が中央部と比べて起こりにくいので、この両端部から中央部へ電解液が拡散して枯渇部を補うことができれば部分的な電解液の枯渇を抑制することができる。ここで繊維が正、負極の短い方向に対して0°に配置されている場合、中央部で電解液の枯渇が起こり始めても電解液の拡散に必要な間隙が中央部の電解液の枯渇を補うために電解液が拡散する方向に確保されているためこの部分の電解液の枯渇を抑制することができるが、90°に配置されている場合、電解液の拡散に必要な間隙が電解液が拡散するのに必要な方向に確保されていないため中央部の電解液の枯渇を抑制することができない。このため、セパレータおよび負極に繊維を固定する場合、正、負極の短い方向に対して0°に配置されている方が好ましい。
【0050】
しかし、セパレータおよび正、負極に繊維を固定する場合、正、負極の短い方向に対して0°に配置されていなければ効果が現れない訳ではなく、ある角度までは効果を保つことができる。(表2)よりセパレータにポリエチレン繊維を固定する場合、角度が大きくなるほど充放電サイクル寿命特性が低下し、500サイクル以上の特性を確保するためにはポリエチレン繊維を固定する角度は、正、負極の短い方向に対して30°以下でなければならない。
【0051】
【表2】
【0052】
なお、本実施例では、セパレータに関しては正極との対向面のみにポリエチレン粒子および繊維を固定した場合について示したが、負極との対向面のみに固定した場合、および正、負極両方の対向面に固定した場合においても本発明の範囲で同様の効果が得られた。正、負極に関しては負極表面のみにポリエチレン繊維を固定した場合について示したが負極両面に固定した場合においても本発明の範囲で同様の効果が得られた。また、正極に関しても負極と同様の効果が得られた。また、負極表面にポリエチレン粒子を固定した場合においても同様の効果が得られた。さらに、セパレータおよび表面に固定した粒子、繊維はポリエチレンを用いた場合について示したが、他のポリオレフィン微多孔膜および粒子、繊維を用いても本発明の範囲で同様の効果が得られた。
【0053】
【発明の効果】
以上のように本発明では、表面粗度が1μm以上20μm以下である正極、負極、セパレータを用いることにより、正、負極間にできる間隙の部分に電解液を多く保液することができ、電解液と正、負極のガス発生もしくは被膜形成等の不可逆反応による電解液の枯渇を迎えることができる。また、正、負極間における電解液の拡散がこの間隙を通ることにより容易になり、極板上での部分的な電解液の枯渇も抑制されるため優れた充放電サイクル寿命特性を有する電池を提供することができる。
【図面の簡単な説明】
【図1】本発明の円筒型リチウムイオン二次電池の縦断面図
【符号の説明】
1 セパレータ
2 正極板
3 負極板
4 正極リード片
5 負極リード片
6 底部絶縁板
7 電池ケース
8 上部絶縁板
9 ガスケット
10 封口板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to electrolyte holding and positive electrode diffusion between a positive electrode and a negative electrode of a lithium secondary battery.
[0002]
[Prior art]
In recent years, electronic devices such as personal computers and mobile phones have been rapidly reduced in size and weight and are cordless, and secondary batteries having high energy density are required as power sources for driving these devices. Among them, a lithium secondary battery using lithium as an active material is particularly expected as a battery having a high voltage and a high energy density. Conventionally, this battery uses metallic lithium as a negative electrode and molybdenum disulfide, manganese dioxide, vanadium pentoxide, etc. as a positive electrode, and a 3V class battery has been realized.
[0003]
However, when metallic lithium is used for the negative electrode, dendritic (dendritic) lithium is precipitated during charging, and the dendritic lithium deposited on the electrode plate is separated from the electrode plate with repeated charge and discharge, and is dissolved in the electrolyte. , Floated and contacted with the positive electrode to cause a short circuit, charging and discharging efficiency was less than 100%, and the cycle life was shortened. In addition, dendritic lithium has a problem in terms of safety because of its large surface area and high reactivity.
[0004]
Therefore, recently, lithium ion secondary batteries using a carbon material for the negative electrode and a lithium-containing oxide for the positive electrode instead of metallic lithium have been the focus of research and have been partially commercialized. In this battery, lithium is present in the negative electrode in a state where it is occluded as ions in carbon, and is therefore considered to be very safe compared to conventional metal lithium systems.
[0005]
[Problems to be solved by the invention]
However, since the lithium-containing oxide used for the positive electrode of the lithium ion secondary battery system has a high potential of 4 V with respect to lithium, the organic solvent in the electrolytic solution is more easily oxidatively decomposed than the conventional 3 V class lithium secondary battery. In addition, the electrolyte is depleted with charge and discharge, while carbon used for the negative electrode, particularly graphite, is highly reactive with the electrolyte, and here the electrolyte is easily depleted. Further, the depletion of the electrolytic solution occurs from the central portion in the short direction of the positive and negative electrodes where the temperature tends to rise. Such partial depletion of the electrolyte on the electrode plate may lead to a decrease in charge / discharge cycle life.
[0006]
Therefore, if the electrolyte can be easily diffused in the center in the short direction of the positive and negative electrodes, partial depletion of the electrolyte on the electrode plate is unlikely to occur, but the structure of the lithium ion secondary battery is, for example, In the cylindrical type, as shown in FIG. 1, a strip-like
[0007]
In order to deal with such drawbacks, Japanese Patent Laid-Open No. 6-333550 reports a method in which a separator is provided with a groove and an electrolytic solution penetrates into the electrode group. However, since the electrode group is wound with high tension during construction, the grooved portion becomes thinner when the separator is grooved, so the strength becomes weaker and the elongation rate of that portion may change or it may break if severe There is.
[0008]
The present invention solves the above-mentioned problems, and prevents the electrolyte from depleting by increasing the amount of the electrolyte between the positive and negative electrodes, and facilitates the diffusion of the electrolyte in the electrode group. An object of the present invention is to provide a lithium secondary battery that suppresses partial depletion of electrolyte on the plate and has excellent charge / discharge cycle life characteristics.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The present invention uses positive and negative electrodes having polyolefin particles or polyolefin fibers fixed on at least one surface and having a surface roughness of 5 μm or more and 10 μm or less . In addition, the polyolefin particles or polyolefin fibers fixed polyethylene, polypropylene is more preferable.
[0010]
With such a configuration, it is possible to hold a large amount of electrolyte in the gap formed between the positive and negative electrodes while maintaining the strength of the separator, and gas generation or film formation of the electrolyte and positive and negative electrodes, etc. The depletion of the electrolyte due to the irreversible reaction can be suppressed. In addition, it is easy to diffuse the electrolyte between the positive and negative electrodes through this gap, and it is possible to suppress partial depletion of the electrolyte on the electrode plate. Can be provided.
[0011]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0012]
FIG. 1 shows a longitudinal sectional view of a cylindrical lithium ion secondary battery (diameter 17 mm, total height 50 mm) used in this example. As is clear from this figure, the electrode group is formed by winding the strip-like
[0013]
( Reference Example 1)
The positive electrode was prepared by mixing Li 2 CO 3 and Co 3 O 4 and calcining at 900 ° C. for 10 hours for 10 parts by weight of
[0014]
Moreover, the negative electrode was produced as follows. First, after pulverized and classified so as to have an average particle size of about 20 μm, 3 parts by weight of styrene / butadiene rubber as a binder was mixed, and then added to 100 parts by weight of 1% carboxymethylcellulose aqueous solution with respect to graphite. The mixture was stirred and mixed to obtain a negative electrode paste. A negative electrode mixture paste was applied to both sides of a copper foil having a current collector thickness of 20 μm, dried and then rolled using a rolling roller, and cut into a predetermined size to obtain a negative electrode plate.
[0015]
As the separator, a polyethylene separator having a thickness of 0.1 μm was fixed on one side of a polyethylene separator having a thickness of 20 μm. And the electrode group was comprised so that the rough surface part of this separator might oppose a positive electrode.
[0016]
The non-aqueous electrolyte used was a solution in which 1.5 mol / liter LiPF 6 was dissolved in a solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 3. . This was designated as Battery A.
[0017]
( Reference Example 2)
A battery was prepared in the same manner as in ( Reference Example 1) except that polyethylene particles were fixed to one side of a polyethylene separator having a thickness of 20 μm and a separator having a surface roughness of 1.0 μm was used. This was designated as Battery B.
[0018]
( Reference Example 3)
A battery was prepared in the same manner as in ( Reference Example 1) except that polyethylene particles were fixed to one side of a polyethylene separator having a thickness of 20 μm and a separator having a surface roughness of 5.0 μm was used. This was designated as Battery C.
[0019]
( Reference Example 4)
A battery was prepared in the same manner as in ( Reference Example 1) except that polyethylene particles were fixed on one side of a polyethylene separator having a thickness of 20 μm, and a separator having a surface roughness of 10.0 μm was used. This was designated as Battery D.
[0020]
( Reference Example 5)
A battery was prepared in the same manner as in ( Reference Example 1) except that polyethylene particles were fixed to one side of a polyethylene separator having a thickness of 20 μm and a separator having a surface roughness of 20.0 μm was used. This was designated as Battery E.
[0021]
( Reference Example 6)
A battery was prepared in the same manner as in ( Reference Example 1) except that polyethylene particles were fixed to one side of a polyethylene separator having a thickness of 20 μm, and a separator having a surface roughness of 30.0 μm was used. This was designated as Battery F.
[0022]
( Reference Example 7)
A polyethylene fiber is fixed on one side of a polyethylene separator having a thickness of 20 μm so as to be arranged at 0 ° with respect to the short direction of the positive and negative electrodes, and a separator having a surface roughness of 0.1 μm is used ( reference example) A battery similar to 1) was produced. This was designated as battery G.
[0023]
( Reference Example 8)
A polyethylene fiber is fixed on one side of a polyethylene separator having a thickness of 20 μm so as to be arranged at 0 ° with respect to the short direction of the positive and negative electrodes, and a separator having a surface roughness of 1.0 μm is used ( reference example) A battery similar to 1) was produced. This was designated as Battery H.
[0024]
( Reference Example 9)
A polyethylene fiber having a thickness of 20 μm was fixed to one side of a polyethylene separator so that the positive and negative electrodes were arranged at 0 ° with respect to the short direction of the negative electrode, and a separator with a surface roughness of 5.0 μm was used ( reference example) A battery similar to 1) was produced. This was designated as Battery I.
[0025]
( Reference Example 10)
A polyethylene fiber is fixed on one side of a polyethylene separator having a thickness of 20 μm so that the fiber is arranged at 0 ° with respect to the short direction of the positive and negative electrodes, and a separator having a surface roughness of 10.0 μm is used ( reference example) A battery similar to 1) was produced. This was designated as Battery J.
[0026]
( Reference Example 11)
A polyethylene fiber is fixed to one side of a polyethylene separator having a thickness of 20 μm so as to be arranged at 0 ° with respect to the short direction of the positive and negative electrodes, and a separator having a surface roughness of 20.0 μm is used ( reference example) A battery similar to 1) was produced. This was designated as Battery K.
[0027]
( Reference Example 12)
A polyethylene fiber is fixed to one side of a polyethylene separator having a thickness of 20 μm so as to be arranged at 0 ° with respect to the short direction of the positive and negative electrodes, and a separator having a surface roughness of 30.0 μm is used ( reference example) A battery similar to 1) was produced. This was designated as a battery L.
[0028]
( Reference Example 13)
Thick positive polyethylene fibers on one side of 20μm polyethylene separator, and fixed so as to be disposed 90 ° with respect to the short direction of the negative electrode, except that the surface roughness using a separator Les chromatography data is 5.0μm is A battery similar to ( Reference Example 1) was produced. This was designated as Battery M.
[0029]
( Reference Example 14 )
The negative electrode was prepared in (Reference Example 1), and polyethylene fiber was fixed on one side so as to be arranged at 0 ° with respect to the short direction of the negative electrode, and the surface roughness was 0.1 μm. The separator used the thing which has not performed the surface treatment made from polyethylene with a thickness of 20 micrometers. A battery was prepared in the same manner as in (Reference Example 1) except for the above. This was designated as Battery N.
[0030]
( Reference Example 15 )
The negative electrode was prepared in (Reference Example 1), except that a polyethylene fiber was fixed on one side so as to be arranged at 0 ° with respect to the short direction of the negative electrode, and the surface roughness was 1.0 μm. A battery similar to ( Reference Example 14 ) was produced. This was designated as battery O.
[0031]
(Example 1 )
The negative electrode was prepared in (Reference Example 1), except that a polyethylene fiber was fixed on one side so as to be arranged at 0 ° with respect to the short direction of the negative electrode, and the surface roughness was 5.0 μm. A battery similar to ( Reference Example 14 ) was produced. This was designated as battery P.
[0032]
(Example 2 )
The negative electrode was prepared in (Reference Example 1), except that a polyethylene fiber was fixed on one side so as to be arranged at 0 ° with respect to the short direction of the negative electrode, and the surface roughness was 10.0 μm. A battery similar to ( Reference Example 14 ) was produced. This was designated as Battery Q.
[0033]
( Reference Example 16 )
The negative electrode was prepared in (Reference Example 1), except that a polyethylene fiber was fixed on one side so as to be arranged at 0 ° with respect to the short direction of the negative electrode, and the surface roughness was 20.0 μm. A battery similar to ( Reference Example 14 ) was produced. This was designated as Battery R.
[0034]
( Reference Example 17 )
The negative electrode was prepared in (Reference Example 1), except that a polyethylene fiber was fixed on one side so that it was placed at 0 ° with respect to the short direction of the negative electrode, and the surface roughness was 30.0 μm. A battery similar to ( Reference Example 14 ) was produced. This was designated as battery S.
[0035]
(Example 3 )
The negative electrode was prepared in (Reference Example 1), except that a polyethylene fiber was fixed on one side so as to be arranged at 90 ° with respect to the short direction of the negative electrode, and the surface roughness was 5.0 μm. A battery similar to ( Reference Example 14 ) was produced. This was designated as battery T.
[0036]
(Comparative Example 1)
A battery was manufactured in the same manner as in ( Reference Example 1) except that a separator made of polyethylene having a thickness of 20 μm and not subjected to surface treatment, and positive and negative electrodes not subjected to surface treatment were used. This was designated as a battery U.
[0037]
(Reference Example 18 )
A polyethylene fiber is fixed to one side of a polyethylene separator having a thickness of 20 μm so as to be arranged at 15 ° with respect to the short direction of the positive and negative electrodes, and a separator having a surface roughness of 5.0 μm is used (reference example) A battery similar to 1) was produced. This was designated as Battery V.
[0038]
(Reference Example 19 )
A polyethylene fiber is fixed to one side of a polyethylene separator having a thickness of 20 μm so as to be arranged at 30 ° with respect to the short direction of the positive and negative electrodes, and a separator having a surface roughness of 5.0 μm is used (reference example) A battery similar to 1) was produced. This was designated as battery W.
[0039]
(Reference Example 20 )
A polyethylene fiber is fixed to one side of a polyethylene separator having a thickness of 20 μm so as to be arranged at 45 ° with respect to the short direction of the positive and negative electrodes, and a separator having a surface roughness of 5.0 μm is used ( reference example) A battery similar to 1) was produced. This was designated as Battery X.
[0040]
(Reference Example 21 )
A polyethylene fiber is fixed to one side of a polyethylene separator having a thickness of 20 μm so as to be arranged at 60 ° with respect to the short direction of the positive and negative electrodes, and a separator having a surface roughness of 5.0 μm is used (reference example) A battery similar to 1) was produced. This was designated as Battery Y.
[0041]
Here, the surface roughness described above is a value measured in accordance with JIS B 0601, which is a centerline roughness. A surface roughness measuring instrument (SURCOM, manufactured by Tokyo Seimitsu Co., Ltd.) is used to drive the surface. The measurement was performed under the conditions of 0.3 mm / second, a measurement length of 4.0 mm, a stylus load of 0.07 g, and a cutoff value of 0.8 mm.
[0042]
Next, 5 cells of each of the batteries A to Y were prepared, the ambient temperature was 20 ° C., the upper limit voltage was set to 4.2 V, and constant current / constant voltage charging was performed at a maximum current of 560 mA for 2 hours. For discharging, the battery in this charged state was discharged at a constant current of 800 mA and a discharge end potential of 3.0 V. Then, the discharge capacity at the 10th cycle was set as the initial capacity, and the rate test of the battery was performed there to calculate the 2C discharge maintenance rate.
[0043]
The 2C discharge maintenance ratio was the ratio (%) of the capacity during 2C (1600 mA) discharge to the capacity during 0.2 C (160 mA) discharge.
[0044]
The cycle number when the capacity was reduced to half the initial capacity was defined as the cycle life. Table 1 shows the average value of the 5 cells for the cycle life and 2C discharge maintenance ratio at this time.
[0045]
[Table 1]
[0046]
From (Table 1) result, battery A~T is charge-discharge cycle life than the batteries U is increased. Moreover, the charge / discharge cycle life increased as the surface roughness of the separator and the negative electrode increased. This is because a large amount of electrolyte can be retained in the gap between the positive and negative electrodes, and depletion of the electrolyte due to irreversible reactions such as gas generation or film formation between the positive and negative electrodes can be suppressed. is there.
[0047]
However, in the batteries A, G and N, the charge / discharge cycle life is not so increased as compared with the battery U. That is, with this degree of surface roughness, the amount of electrolyte that can be held between the positive and negative electrodes is small, and it is not possible to suppress depletion of the electrolyte. For this reason, in order to improve the charge / discharge cycle life characteristics, the surface roughness needs to be at least 1.0 μm or more.
[0048]
In addition, the batteries F, L, and S show sufficient characteristics with respect to the charge / discharge cycle life, but the 2C discharge maintenance ratio is significantly lower than that of other batteries. This is because the distance between the positive and negative electrodes increases as the surface roughness increases. That is, the organic solvent has a low ionic conductivity, and in the case of a large current discharge, the movement of lithium ions in the electrolytic solution becomes rate limiting, and if the distance between the positive and negative electrodes becomes too large, it becomes difficult to perform a large current discharge. Furthermore, when the surface roughness is too large, the thickness becomes too thick, and the proportion of positive and negative electrodes in the battery decreases, leading to a decrease in battery capacity. Moreover, if the thickness of the separator is reduced in order to ensure the battery capacity, the microporous membrane portion becomes very thin and there is a risk of an internal short circuit or the like. For this reason, when the surface roughness is 30 μm or more, the charge / discharge cycle life is satisfactory, but the surface roughness must be 20 μm or less in consideration of large current discharge and safety.
[0049]
When fixing the fiber to the separator, the charge / discharge cycle life is longer when the battery is arranged at 90 ° (battery I) than when the battery is arranged at 0 ° with respect to the short direction of the positive and negative electrodes (battery M). Increase. The same applies to the case where fibers are fixed to the negative electrode (batteries P and T). This is because reactions such as oxidative decomposition of the electrolytic solution begin to occur at the central portion in the short direction of the positive and negative electrodes, where the temperature tends to rise. At this time, electrolyte depletion is less likely to occur at both ends compared to the central portion, so partial electrolyte depletion can be suppressed if the electrolyte diffuses from both ends to the central portion to compensate for the depleted portion. be able to. Here, when the fibers are arranged at 0 ° with respect to the short direction of the positive and negative electrodes, the gap necessary for the diffusion of the electrolyte does not deplete the electrolyte in the center even if the electrolyte begins to deplete in the center. In order to compensate, the electrolyte solution is secured in the direction of diffusion, so that it is possible to suppress depletion of this portion of the electrolyte solution, but when it is arranged at 90 °, the gap necessary for the electrolyte solution diffusion is Is not ensured in the direction necessary for diffusion, it is not possible to suppress the depletion of the electrolyte in the center. For this reason, when fixing a fiber to a separator and a negative electrode, it is more preferable to arrange | position at 0 degree with respect to the short direction of a positive and negative electrode.
[0050]
However, when fixing the fibers to the separator, the positive electrode, and the negative electrode, the effect does not appear unless it is arranged at 0 ° with respect to the short direction of the positive electrode and the negative electrode, and the effect can be maintained up to a certain angle. (Table 2) When fixing polyethylene fiber to the separator, the charge / discharge cycle life characteristics decrease as the angle increases, and in order to secure the characteristics of 500 cycles or more, the angle at which the polyethylene fiber is fixed is positive or negative. Must be no more than 30 ° in the short direction.
[0051]
[Table 2]
[0052]
In this example, the separator was shown for the case where polyethylene particles and fibers were fixed only on the surface facing the positive electrode, but when the separator was fixed only on the surface facing the negative electrode, and on both the positive and negative electrode facing surfaces. Even when fixed, the same effect was obtained within the scope of the present invention. For the positive and negative electrodes, the case where polyethylene fibers were fixed only on the negative electrode surface was shown, but similar effects were obtained within the scope of the present invention even when fixed on both surfaces of the negative electrode. Moreover, the same effect as a negative electrode was acquired regarding the positive electrode. The same effect was obtained when polyethylene particles were fixed on the negative electrode surface. Further, the case where polyethylene was used as the separator and the particles and fibers fixed on the surface was shown, but the same effect was obtained within the scope of the present invention even when other polyolefin microporous membranes, particles and fibers were used.
[0053]
【The invention's effect】
As described above, in the present invention, by using a positive electrode, a negative electrode, and a separator having a surface roughness of 1 μm or more and 20 μm or less, a large amount of electrolyte can be retained in a gap portion formed between the positive and negative electrodes. Electrolyte depletion can be achieved due to irreversible reactions such as gas generation between the liquid and positive and negative electrodes or film formation. In addition, since the electrolyte can be easily diffused between the positive and negative electrodes through the gap, and partial electrolyte depletion on the electrode plate is also suppressed, a battery having excellent charge / discharge cycle life characteristics can be obtained. Can be provided.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a cylindrical lithium ion secondary battery of the present invention.
DESCRIPTION OF
Claims (1)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP30486198A JP4712139B2 (en) | 1997-10-27 | 1998-10-27 | Lithium secondary battery |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP29384697 | 1997-10-27 | ||
JP9-293846 | 1997-10-27 | ||
JP1997293846 | 1997-10-27 | ||
JP30486198A JP4712139B2 (en) | 1997-10-27 | 1998-10-27 | Lithium secondary battery |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH11195410A JPH11195410A (en) | 1999-07-21 |
JP4712139B2 true JP4712139B2 (en) | 2011-06-29 |
Family
ID=26559581
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP30486198A Expired - Fee Related JP4712139B2 (en) | 1997-10-27 | 1998-10-27 | Lithium secondary battery |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP4712139B2 (en) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7459234B2 (en) | 2003-11-24 | 2008-12-02 | The Gillette Company | Battery including aluminum components |
JP4705334B2 (en) * | 2004-03-19 | 2011-06-22 | 株式会社巴川製紙所 | Separator for electronic parts and method for manufacturing the same |
JP5500425B2 (en) * | 2009-06-04 | 2014-05-21 | 三菱樹脂株式会社 | Non-aqueous lithium secondary battery |
JP5811156B2 (en) * | 2013-10-21 | 2015-11-11 | 三洋電機株式会社 | Nonaqueous electrolyte secondary battery |
CN105161768A (en) * | 2015-10-10 | 2015-12-16 | 无锡德沃精工设备有限公司 | Vehicle starting type lithium iron phosphate battery |
-
1998
- 1998-10-27 JP JP30486198A patent/JP4712139B2/en not_active Expired - Fee Related
Also Published As
Publication number | Publication date |
---|---|
JPH11195410A (en) | 1999-07-21 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
JP4411690B2 (en) | Lithium ion secondary battery | |
US9520588B2 (en) | Nonaqueous electrolyte secondary cell | |
JPH11238528A (en) | Lithium secondary battery | |
JP3821434B2 (en) | Battery electrode group and non-aqueous electrolyte secondary battery using the same | |
KR20130043308A (en) | Secondary battery | |
JPH05151995A (en) | Nonaqueous electrolyte secondary battery | |
JP2002008730A (en) | Lithium secondary battery | |
JPH10208777A (en) | Non-aqueous electrolyte secondary battery | |
JP4712139B2 (en) | Lithium secondary battery | |
US7166387B2 (en) | Thin battery with an electrode having a higher strength base portion than a tip portion | |
JP4830295B2 (en) | Non-aqueous electrolyte secondary battery | |
JP2000294229A (en) | Nonaqueous electrolytic secondary battery | |
CN114068924A (en) | Negative electrode active material and lithium secondary battery comprising same | |
JP2000040499A (en) | Nonaqueous electrolyte secondary battery | |
JPH0855637A (en) | Nonaqueous electrolytic secondary battery | |
KR20120020893A (en) | Lithium ion capacitor | |
JP4827112B2 (en) | Flat non-aqueous electrolyte secondary battery | |
JP2730641B2 (en) | Lithium secondary battery | |
JP2000306610A (en) | Nonaqueous electrolyte secondary battery | |
JP2005327516A (en) | Charging method of nonaqueous electrolyte secondary battery | |
JPH07142088A (en) | Lithium secondary battery | |
KR100601561B1 (en) | Jelly-roll type electrode assembly and Cylindrical Li Secondary battery with the same | |
JP2003022791A (en) | Lithium secondary battery | |
JPH11111302A (en) | Electrode for battery, and battery using the same | |
JP5254722B2 (en) | Lithium secondary battery |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20050915 |
|
A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20050915 |
|
RD01 | Notification of change of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7421 Effective date: 20051013 |
|
A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20090428 |
|
A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20090611 |
|
A02 | Decision of refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A02 Effective date: 20090707 |
|
A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20110121 |
|
A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20110323 |
|
FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20140401 Year of fee payment: 3 |
|
LAPS | Cancellation because of no payment of annual fees |