JP3615472B2 - Non-aqueous electrolyte battery - Google Patents
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- JP3615472B2 JP3615472B2 JP2000267626A JP2000267626A JP3615472B2 JP 3615472 B2 JP3615472 B2 JP 3615472B2 JP 2000267626 A JP2000267626 A JP 2000267626A JP 2000267626 A JP2000267626 A JP 2000267626A JP 3615472 B2 JP3615472 B2 JP 3615472B2
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Description
【０００１】
【発明の属する技術分野】
本発明は、非水電解質電池に関する。さらに詳しくは、本発明は、特定の結着剤を含む負極および塩濃度の低い非水電解質を用いた高率放電特性および低温特性に優れ、安全性の高い非水電解質電池に関する。
【０００２】
【従来の技術】
近年、携帯用電子機器の電源として利用されている非水電解質電池は、正極にリチウム含有遷移金属酸化物を用い、負極にリチウムの吸蔵・放出が可能な炭素材料を用いているため、高出力で高エネルギー密度である。ここで、これらの電池が有する電極は、活物質同士を結合するための結着剤を含んでおり、負極には、結着剤としてポリビニリデンジフルオライド（ＰＶＤＦ）やスチレンブタジエンゴム（ＳＢＲ）などが用いられている。
【０００３】
しかし、負極に充分な強度を付与するには、多量の結着剤を活物質に混合する必要がある。そのため活物質である炭素材料の表面が結着剤で被覆されてしまい、充放電反応に寄与する活物質表面が減少する。これを補うためには、非水電解質の塩濃度を高くする必要があるが、塩濃度が高くなると、電池の高率放電特性や低温特性が低下し、また、電池温度が上昇し易くなるという不都合がある。
【０００４】
また、電池の高率放電特性等は、非水電解質と電極との親和性にも大きく影響される。非水電解質と電極との親和性が高すぎると、電池内部における非水電解質の分布が不均一になり、高率放電特性が損なわれる。
【０００５】
【発明が解決しようとする課題】
本発明は、高率放電特性や低温特性に優れ、かつ、安全性の高い非水電解質電池を得ることを目的とする。
【０００６】
【課題を解決するための手段】
本発明は、リチウム含有遷移金属酸化物からなる正極、黒鉛からなる負極、前記正極と負極との間に介在するセパレータおよび非水溶媒にＬｉＰＦ6を溶解した非水電解質を具備する非水電解質電池であって、前記負極が、前記黒鉛１００重量部あたり０．６〜１．７重量部の粒子状変性スチレンブタジエンゴムおよび０．７〜１．２重量部の増粘剤を両者の合計量が１．３〜２．４重量部になるように含有し、前記非水電解質におけるＬｉＰＦ6の濃度が、０．６〜１．０５モル／リットルであり、前記黒鉛の平均粒径が２０〜３０μｍであり、比表面積が５ｍ 2 ／ｇ以下であり、前記粒子状変性スチレンブタジエンゴムが、コアシェル型粒子からなり、前記コアシェル型粒子は、コア部分にアクリロニトリル単位を含んでいることを特徴とする非水電解質電池に関する。
【０００７】
前記粒子状変性スチレンブタジエンゴムのＦＴ−ＩＲ測定で得られる吸収スペクトルにおいて、アクリロニトリル単位のＣ≡Ｎ伸縮振動に基づく吸収強度は、ブタジエン単位のＣ＝Ｃ伸縮振動に基づく吸収強度の０．１〜２倍であることが好ましい。ここで、吸収強度とは、スペクトルのベースラインからみた吸収ピークの高さをいう。
前記粒子状変性スチレンブタジエンゴムの平均粒径の好適範囲は、０．０５〜０．４μｍである。
前記増粘剤は、カルボキシメチルセルロースであることが好ましい。
非水電解質におけるＬｉＰＦ6の濃度は、０．７〜０．９モル／リットルがさらに好適である。
【０００８】
前記正極は、前記リチウム含有遷移金属酸化物１００重量部あたり０．４〜２重量部の粒子状変性アクリルゴムを含み、前記粒子状変性アクリルゴムは、２−エチルヘキシルアクリレート単位、アクリル酸単位およびアクリロニトリル単位を含む共重合体からなることが好ましい。
前記粒子状変性アクリルゴムのＦＴ−ＩＲ測定で得られる吸収スペクトルにおいて、２−エチルヘキシルアクリレート単位およびアクリル酸単位のＣ＝Ｏ伸縮振動に基づく吸収強度は、アクリロニトリル単位のＣ≡Ｎ伸縮振動に基づく吸収強度の３〜５０倍であることが好ましい。
【０００９】
【発明の実施の形態】
本発明は、特定の結着剤および増粘剤を特定の比率で含む負極と塩濃度の低い非水電解質とを用いることにより、また、特定の結着剤を特定の比率で含む正極を前記負極および前記非水電解質とともに用いることにより、非水電解質電池の高率放電特性、低温特性、安全性等を向上させた点に特徴を有する。
【００１０】
負極は、例えば負極合剤と芯材（集電体）とからなっている。負極合剤は、負極活物質、粒子状変性スチレンブタジエンゴム、増粘剤などを所定の割合で配合して調製される。負極は、例えば負極合剤を銅箔などの金属箔やパンチングメタルなどの芯材の表面に塗着または充填し、圧延し、切断すれば得られる。電池の小型軽量化の観点から、芯材の厚さは一般に８〜２０μｍ程度であり、負極の厚さは一般に８０〜２００μｍである。
【００１１】
負極活物質としては、黒鉛などの炭素粉末を用いる。なかでも鱗片状黒鉛、球状人造黒鉛などが好ましく用いられる。黒鉛の平均粒径は、２０〜３０μｍが好適である。また、黒鉛の比表面積は５ｍ 2 ／ｇ以下であり、例えば４〜５ｍ2／ｇである。
【００１２】
粒子状変性スチレンブタジエンゴムは、コアシェル型粒子であり、コアシェル型粒子のコア部分はアクリロニトリル単位を含み、ゴム弾性を有する。コア部分は、例えばアクリロニトリル単位、スチレン単位、ブタジエン単位、アクリレート単位などを含む共重合体を適当な架橋剤で充分に架橋させたものである。また、シェル部分は、粘性の高い重合体からなり、例えばアクリレート単位、スチレン単位などを含む共重合体からなる。
【００１３】
コアシェル型粒子は、例えば架橋剤を含むコア部分の原料モノマー混合物を重合させてラテックスを製造した後、ラテックス粒子にシェル部分の原料モノマー混合物をグラフト重合させる二段階の工程によって製造できる。このときコア部分の原料モノマーにアクリロニトリルを含有させると、弾性率の高いコア部分を得ることができる。
【００１４】
前記粒子状変性スチレンブタジエンゴムは、そのＦＴ−ＩＲ測定で得られる吸収スペクトルにおいて、アクリロニトリル単位のＣ≡Ｎ伸縮振動に基づく吸収強度が、ブタジエン単位のＣ＝Ｃ伸縮振動に基づく吸収強度の０．１〜２倍となる程度にアクリロニトリル単位とブタジエン単位を含んでいることが好ましい。アクリロニトリル単位のＣ≡Ｎ伸縮振動に基づく吸収強度が、ブタジエン単位のＣ＝Ｃ伸縮振動に基づく吸収強度の０．１倍未満になると、粒子状変性スチレンブタジエンゴムを含ませても充分な強度の負極が得られなくなったり、活物質の表面が粒子状変性スチレンブタジエンゴムで覆われすぎたりする。一方、アクリロニトリル単位のＣ≡Ｎ伸縮振動に基づく吸収強度が、ブタジエン単位のＣ＝Ｃ伸縮振動に基づく吸収強度の２倍をこえると、結着剤のゴム弾性が低下し、芯材から合剤が剥離しやすくなる。
【００１５】
粒子状変性スチレンブタジエンゴムの平均粒径は、少量の使用で充分な強度の負極を得ることができることなどから、０．０５〜０．４μｍであることが好ましい。平均粒径が小さすぎると、活物質の表面の大部分が粒子状変性スチレンブタジエンゴムで被覆されてしまい、大きすぎると、活物質粒子間の距離が大きくなって負極内部の導電性が低下する。
【００１６】
負極合剤における粒子状変性スチレンブタジエンゴムの配合量は、負極活物質である炭素材料１００重量部に対して、０．６〜１．７重量部が適量である。粒子状変性スチレンブタジエンゴムの量が少なすぎると、充分な強度の負極が得られず、芯材から合剤が剥がれたりすることがあり、多すぎると、活物質の反応表面積が小さくなって高率放電特性がわるくなる。
なお、従来のＰＶＤＦの場合、負極合剤における好適配合量は、負極活物質１００重量部に対して、５〜１０重量部であり、ＳＢＲの場合でも２〜５重量部である。従って、本発明に係る負極合剤は、結着剤の含有量が従来に比べて著しく低減されている。
【００１７】
負極合剤に用いる増粘剤としては、例えばカルボキシメチルセルロース（ＣＭＣ）などのセルロース系増粘剤、エチレンとビニルアルコールとの共重合体などが用いられる。これらは単独で用いてもよく、２種以上を組み合わせて用いてもよい。これらのうちではＣＭＣがよく用いられる。
【００１８】
負極合剤における増粘剤の配合量は、負極活物質である炭素材料１００重量部に対して、０．７〜１．２重量部が適量である。増粘剤の配合量が少なすぎると、ペースト状の負極合剤が得られず、芯材から合剤が剥がれやすくなり、多すぎると、活物質が増粘剤で覆われてしまい、その反応表面積が小さくなる。
【００１９】
ただし、粒子状変性スチレンブタジエンゴムおよび増粘剤の合計量は、負極活物質である炭素材料１００重量部に対して、１．３〜２．４重量部である必要がある。前記合計量が１．３重量部未満になると、活物質粒子同士を充分に結着させることができず、負極の強度が不充分となり、多すぎると、活物質が結着剤や増粘剤で覆われてしまい、その反応表面積が小さくなる。
【００２０】
正極は、例えば正極合剤と芯材（集電体）とからなっている。正極合剤は、正極活物質、導電剤、結着剤などを所定の割合で配合して調製される。正極は、例えば正極合剤をアルミニウム箔などの金属箔やパンチングメタルなどの芯材の表面に塗着または充填し、圧延し、切断すれば得られる。電池の小型軽量化の観点から、芯材の厚さは一般に８〜２０μｍ程度であり、正極の厚さは一般に８０〜２００μｍである。
【００２１】
正極活物質であるリチウム含有遷移金属酸化物としては、例えばＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉＭｎ２Ｏ４などが用いられる。これらは単独で用いてもよく、２種以上を組み合わせて用いてもよい。
【００２２】
正極合剤に用いる導電剤としては、例えば鱗片状黒鉛などの天然黒鉛、気相成長黒鉛などの人造黒鉛、アセチレンブラックなどのカーボンブラック類などが用いられる。これらは単独で用いてもよく、２種以上を組み合わせて用いてもよい。
【００２３】
正極合剤に用いる結着剤としては、粒子状変性アクリルゴム、ＰＶＤＦ等を用いることができるが、粒子状変性アクリルゴムを用いることが好ましい。粒子状変性アクリルゴムは、水や有機溶媒を分散媒とする分散液として入手できるが、有機溶媒を分散媒とする分散液の方が好ましい。また、粒子状変性アクリルゴムは、０．０５〜０．３μｍの平均粒径を有するものが、結着力、活物質密度および空隙率のバランスのよい正極を得ることができる点で好ましい。
【００２４】
正極合剤における粒子状変性アクリルゴムの配合量は、正極活物質１００重量部に対して０．４〜２重量部が好適である。粒子状変性アクリルゴムの配合量が少なすぎると、充分な強度の正極が得られず、芯材から合剤が剥がれたりすることがあり、多すぎると、正極の空隙率が小さくなって活物質の反応表面積が小さくなり、高率放電特性がわるくなる。
【００２５】
本発明の非水電解質電池において、正極合剤の結着剤として粒子状変性アクリルゴムを用いると、負極と非水電解質との親和性、および正極と非水電解質との親和性が両者ともに好適となり、そのバランスも優れたものとなるため、電池内部における非水電解質の分布が均一になり、低温特性や高率放電特性に特に優れた電池が得られる。
【００２６】
電極と非水電解質との親和性は、電極の表面と非水電解質（非水電解液）との接触角によって評価することができる。接触角の値は、非水電解質の種類、活物質密度等によって変化するが、１０〜３０°が好適範囲である。接触角が低すぎると、電極が非水電解質を吸収し過ぎて電池の高率放電特性が不充分となり、接触角が大きすぎると、電極が非水電解質をほとんど吸収しないため、やはり電池の高率放電特性が低下する。
【００２７】
前記粒子状変性アクリルゴムは、２−エチルヘキシルアクリレート単位、アクリル酸単位およびアクリロニトリル単位を含む共重合体からなることが好ましい。また、そのＦＴ−ＩＲ測定で得られる吸収スペクトルにおいて、２−エチルヘキシルアクリレート単位およびアクリル酸単位のＣ＝Ｏ伸縮振動に基づく吸収強度が、アクリロニトリル単位のＣ≡Ｎ伸縮振動に基づく吸収強度の３〜５０倍であることが好ましい。前記Ｃ＝Ｏ伸縮振動に基づく吸収強度が、前記Ｃ≡Ｎ伸縮振動に基づく吸収強度の３倍未満になると、粒子状変性アクリルゴムの結着力が低下し、５０倍を超えると、粒子状変性アクリルゴムのゴム弾性が不充分となり、正極合剤の強度が弱くなる。
【００２８】
ＦＴ−ＩＲ測定において、粒子状変性スチレンブタジエンゴムおよび粒子状変性アクリルゴムの吸収スペクトルは、例えば粒子状変性スチレンブタジエンゴムおよび粒子状変性アクリルゴムをそれぞれＫＢｒ板上に塗布したものを用いて測定すればよい。ここで、一般にブタジエン単位のＣ＝Ｃ伸縮振動に基づく吸収は、８８０〜９４０ｃｍ−１付近に見られ、２−エチルヘキシルアクリレート単位およびアクリル酸単位のＣ＝Ｏ伸縮振動に基づく吸収は、１７００〜１７６０ｃｍ−１付近に見られ、アクリロニトリル単位のＣ≡Ｎ伸縮振動に基づく吸収は、２２００〜２２８０ｃｍ−１付近に見られる。
【００２９】
正極および負極を、両者の間にセパレータを介在させて積層すれば極板群が得られる。極板群は、さらに捲回してもよい。セパレータとしては、ポリエチレン製微多孔膜などが用いられ、厚さは一般に１０〜４０μｍである。角形電池を得る場合、捲回された極板群は、断面が略楕円形になるように一方向から圧縮される。
【００３０】
本発明の非水電解質電池の一例である角形電池を極板群の捲回方向に対して平行な面で切断した横断面図を図１に示す。図中、１は角形の電池ケースを示し、その内部に極板群が充填されている。極板群は、シート状の正極板２およびシート状の負極板３を、両者の間にセパレータ４を介在させて積層し、捲回し、さらに一定の偏平率に圧縮したものである。
【００３１】
非水電解質に用いる非水溶媒としては、従来からリチウムイオン二次電池などで用いられている非水溶媒を特に制限なく用いることができる。このようなものとして、例えばエチレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、プロピレンカーボネートなどが挙げられる。これらは単独で用いてもよく、２種以上を組み合わせて用いてもよい。
【００３２】
非水電解質におけるＬｉＰＦ６の濃度は、０．６〜１．０５モル／リットルである。ＬｉＰＦ６の濃度が０．６モル／リットル未満になると、電池の機能が損なわれ、１．０５モル／リットルをこえると、電池の安全性が損なわれる。高率放電特性や低温特性に優れ、かつ、特に安全性の高い非水電解質電池を得るには、ＬｉＰＦ６の濃度が０．７〜０．９モル／リットルであることが好ましい。
【００３３】
【実施例】
次に、本発明を実施例および比較例に基づいて具体的に説明する。ただし、本発明は以下の実施例に限定されるものではない。
【００３４】
《実施例１〜９および比較例１〜１０》
電池Ａ〜Ｓを以下に示すように作製し、その特性を評価した。
【００３５】
負極の作製
所定の結着剤を用い、電池Ａ〜Ｓに用いる所定の組成の負極合剤を調製した。負極活物質としては、鱗片状黒鉛を、増粘剤としてはカルボキシメチルセルロース（ＣＭＣ）を、結着剤としては表１に示すものを用いた。また、負極合剤における活物質１００重量部に対する結着剤および増粘剤の配合量と、両者の合計を重量部で表１に示す。
【００３６】
【表１】
表１に示す結着剤について以下に説明する。
ＢＭ４００Ｂ：日本ゼオン（株）製の粒子状変性スチレンブタジエンゴム。平均粒径０．２μｍ。そのＦＴ−ＩＲ測定で得られる吸収スペクトルにおいて、アクリロニトリル単位のＣ≡Ｎ伸縮振動に基づく吸収強度は、ブタジエン単位のＣ＝Ｃ伸縮振動に基づく吸収強度の０．５倍である。
【００３８】
その吸収スペクトルを図２に示す。測定条件は、サンプルスキャン回数３２、バックグラウンドスキャン回数３２、分解能４０００、サンプルゲイン１．０であり、測定装置は、顕微ＦＴ−ＩＲ（Ｃｏｎｔｉｎｕμｍ（ニコレー社製）、光源：ＡＶＡＴＡＲ−３６０）を用いた。
【００３９】
測定用の試料は、結着剤をＮ−メチルピロリドンに溶かしたものをＫＢｒ板上に塗布し、乾燥したものを用いた。図２中、２２３７ｃｍ−１付近に見られる吸収ピークがアクリロニトリル単位のＣ≡Ｎ伸縮振動に基づくものであり、９１１ｃｍ−１付近に見られる吸収ピークがブタジエン単位のＣ＝Ｃ伸縮振動に基づくものである。
【００４０】
ＭＰＥ：変性ポリエチレン樹脂。
ＳＢＲ：スチレンブタジエンゴム。
ＰＶＤＦ：ポリビニリデンジフルオライド。
【００４１】
比較のためにＳＢＲのＦＴ−ＩＲ測定で得られる透過スペクトルを図３に示す。測定条件、測定装置等は図２の場合と同様である。図３中には、２２３７ｃｍ−１付近にアクリロニトリル単位のＣ≡Ｎ伸縮振動に基づく吸収ピークが見られない。
【００４２】
得られた活物質、結着剤および増粘剤からなる負極合剤を、厚さ１５μｍの銅箔の芯材の両面に塗布し、厚さ１４０μｍに圧延し、所定の長さに切断し、負極を得た。負極には芯材と同材質の負極リードを接続した。
【００４３】
正極の作製
１００重量部のＬｉＣｏＯ２に対し、結着剤としてＰＶＤＦを４重量部および導電剤としてアセチレンブラック３重量部を配合し、正極合剤を得た。次いで、得られた正極合剤を、厚さ２０μｍのアルミニウム箔の芯材の両面に塗布し、所定の厚さに圧延し、所定の長さに切断し、正極を得た。正極には芯材と同材質の正極リードを接続した。
【００４４】
電池の作製
得られた正極および負極は、両者の間にセパレータを介在させて積層し、捲回して極板群を得た。セパレータとしては、厚さ２７μｍのポリエチレン製微多孔膜を用いた。捲回された極板群は、断面が略楕円形になるように一方向から圧縮した。
【００４５】
非水溶媒である等体積のエチレンカーボネートとエチルメチルカーボネートとの混合物に、表１に示す塩濃度（Ｍ：モル／リットル）になるように、ＬｉＰＦ６を溶解した非水電解質を調製した。
【００４６】
前記極板群は、絶縁リングをその上部および底部に配して所定のアルミニウム製ケース内に３．２ｇの非水電解質とともに収容した。そして、負極リードおよび正極リードを所定の箇所に接続したのち、ケースの開口部を封口板で封口し、非水電解質電池Ａ〜Ｓを完成した。これらの電池は、幅３０ｍｍ、高さ４８ｍｍ、厚さ５ｍｍの角形であり、電池の公称容量は６００ｍＡｈである。
【００４７】
次に、得られた非水電解質電池の評価内容について説明する。
低温特性
非水電解質電池Ａ〜Ｓについて、０℃雰囲気下において、６００ｍＡで電池電圧が４．２Ｖになるまで充電し、このときの充電容量を調べた。結果を表１に示す。
【００４８】
高率放電特性
非水電解質電池Ａ〜Ｓについて、６００ｍＡで電池電圧が４．２Ｖになるまで充電し、１２０ｍＡで電池電圧が３Ｖになるまで放電した。次いで、６００ｍＡで電池電圧が４．２Ｖになるまで充電し、１２００ｍＡで電池電圧が３Ｖになるまで放電した。それぞれの場合について、放電容量を求め、後者の前者に対する比（容量比）を求めた。結果を１００分率で表１に示す。
【００４９】
容量維持率
得られた非水電解質電池Ａ〜Ｓについて、６００ｍＡで電池電圧が４．２Ｖになるまで充電し、６００ｍＡで電池電圧が３Ｖになるまで放電する操作を２００回繰り返した。そして、一回目の放電容量に対する２００回目の放電容量の比を求めた。結果を１００分率で表１に示す。
【００５０】
過充電試験（安全性試験）
得られた非水電解質電池Ａ〜Ｓについて、１２６０ｍＡで電池を充電し続け、電池の表面温度が８０℃に達したときに充電をやめた。その後しばらく電池を放置し、電池の表面温度が９０℃以上に達した電池は×、９０℃未満の電池は○とした。結果を表１に示す。評価が○の電池は、安全性が高いと言える。
【００５１】
表１の結果から、以下のことがわかる。
非水電解質における塩濃度が０．６〜１．０５モル／リットルである電池のうち、粒子状変性スチレンブタジエンゴムを負極合剤に用いている実施例の電池は、いずれも安全性が高いことがわかる。一方、非水電解質における塩濃度が１．１モル／リットルである比較例の電池Ａは、安全性が不充分である。また、非水電解質における塩濃度が０．５５モル／リットルである比較例の電池Ｓは、低温特性、高率放電特性、容量維持率が不充分である。
【００５２】
粒子状変性スチレンブタジエンゴムを負極合剤に用いていない比較例の電池Ｄ〜Ｆは、いずれも安全性、低温特性などが不充分である。また、従来から多用されているＰＶＤＦを負極合剤の結着剤に用いた電池Ｆは、結着剤の配合量が他の電池より多いのにもかかわらず、極板群を作製するときに極板にひびが入るなど、極板強度が不充分であった。
【００５３】
表１は、粒子状変性スチレンブタジエンゴムの配合量は、活物質１００重量部に対して０．６〜１．７重量部が好適であることを示している。結着剤の配合量が０．５重量部の電池Ｈは、負極の作製が困難であったため、電池の評価は行えなかった。また、結着剤の配合量が１．８重量部の電池Ｒは、高率放電特性や容量維持率が不充分である。
【００５４】
表１は、また、増粘剤の配合量は、活物質１００重量部に対して０．７〜１．２重量部が好適であることを示している。増粘剤の配合量が０．７重量部の電池Ｑは、負極の作製が困難であったため、電池の評価は行えなかった。また、結着剤の配合量が１．３重量部の電池Ｋは、高率放電特性や容量維持率が不充分である。
【００５５】
表１は、さらに、粒子状変性スチレンブタジエンゴムおよび増粘剤の合計の配合量は、活物質１００重量部に対して１．３〜２．４重量部が好適であることを示している。合計の配合量が２．５重量部以上の電池ＯおよびＲは、高率放電特性や容量維持率が不充分である。
【００５６】
《実施例１０》
１００重量部のＬｉＣｏＯ2に対し、結着剤として０．５３重量部のＢＭ５００Ｂおよび増粘剤として０．２７重量部のＢＭ７００Ｈを配合したこと以外、実施例２と同様にして正極合剤を得た。次いで、得られた正極合剤を用いて実施例２と同様の電池Ｔを作製し、同様に評価した。結果を表１に示す。
【００５７】
用いた結着剤および増粘剤について以下に説明する。
ＢＭ５００Ｂ：日本ゼオン（株）製の粒子状変性アクリルゴム。そのＦＴ−ＩＲ測定で得られる吸収スペクトルにおいて、２−エチルヘキシルアクリレート単位およびアクリル酸単位のＣ＝Ｏ伸縮振動に基づく吸収ピーク強度は、アクリロニトリル単位のＣ≡Ｎ伸縮振動に基づく吸収ピーク強度の約１０倍である。そのスペクトルを図４に示す。
【００５８】
測定条件、測定装置等は、図２の場合と同様である。図４中、２２４０ｃｍ−１付近に見られる吸収ピークがアクリロニトリル単位のＣ≡Ｎ伸縮振動に基づくものであり、１７３３ｃｍ−１付近に見られる吸収ピークが２−エチルヘキシルアクリレート単位およびアクリル酸単位のＣ＝Ｏ伸縮振動に基づくものである。
【００５９】
ＢＭ７００Ｈ：日本ゼオン（株）製のエチレン単位およびビニルアルコール単位を含む共重合体。そのＦＴ−ＩＲ測定で得られる透過スペクトルを図５に示す。測定条件、測定装置等は図２の場合と同様である。図５中、２８５２ｃｍ−１付近および２９３０ｃｍ−１付近に見られる２種の吸収ピークは、エチレン単位に結合したビニルアルコール単位のＯＨ基に基づくものである。
【００６０】
表１に示すように、評価の結果、電池Ｔの低温特性、高率放電特性および容量維持率は、いずれも実施例１〜９の電池に比べて高く、安全性も優れていた。このことから、正極の結着剤として粒子状変性アクリルゴムを用いることにより、電池の諸特性が飛躍的に向上することがわかる。
【００６１】
【発明の効果】
本発明によれば、高率放電特性や低温特性に優れ、かつ、安全性の高い非水電解質電池を得ることができる。
【図面の簡単な説明】
【図１】本発明の非水電解質電池の一例である角形電池の横断面図である。
【図２】粒子状変性スチレンブタジエンゴムのＦＴ−ＩＲ測定で得られた吸収スペクトルの一例である。
【図３】
ＳＢＲのＦＴ−ＩＲ測定で得られた透過スペクトルの一例である。
【図４】
粒子状変性アクリルゴムのＦＴ−ＩＲ測定で得られた吸収スペクトルの一例である。
【図５】
エチレン単位およびビニルアルコール単位を含む共重合体のＦＴ−ＩＲ測定で得られた透過スペクトルの一例である。
【符号の説明】
１ 電池ケース
２ 正極板
３ 負極板
４ セパレータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte battery. More particularly, the present invention relates to a negative Gokuo and excellent high-rate discharge characteristics and low temperature characteristics with low salt concentration non-aqueous electrolyte, high safety non-aqueous electrolyte battery including a specific binding agent.
[0002]
[Prior art]
In recent years, non-aqueous electrolyte batteries used as power sources for portable electronic devices use a lithium-containing transition metal oxide for the positive electrode and a carbon material capable of occluding and releasing lithium for the negative electrode. High energy density. Here, the electrodes of these batteries include a binder for bonding active materials, and the negative electrode includes polyvinylidene difluoride (PVDF) or styrene butadiene rubber (SBR) as a binder. Etc. are used.
[0003]
However, in order to give sufficient strength to the negative electrode, it is necessary to mix a large amount of binder with the active material. Therefore, the surface of the carbon material that is the active material is coated with the binder, and the surface of the active material that contributes to the charge / discharge reaction is reduced. In order to compensate for this, it is necessary to increase the salt concentration of the non-aqueous electrolyte. However, if the salt concentration increases, the high rate discharge characteristics and low temperature characteristics of the battery decrease, and the battery temperature easily rises. There is an inconvenience.
[0004]
In addition, the high rate discharge characteristics of the battery are greatly affected by the affinity between the nonaqueous electrolyte and the electrode. If the affinity between the nonaqueous electrolyte and the electrode is too high, the distribution of the nonaqueous electrolyte in the battery becomes non-uniform and the high rate discharge characteristics are impaired.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to obtain a non-aqueous electrolyte battery that is excellent in high rate discharge characteristics and low temperature characteristics and has high safety.
[0006]
[Means for Solving the Problems]
The present invention relates to a non-aqueous electrolyte battery comprising a positive electrode made of a lithium-containing transition metal oxide, a negative electrode made of graphite , a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte in which LiPF 6 is dissolved in a non-aqueous solvent. The negative electrode has a total amount of 0.6 to 1.7 parts by weight of particulate modified styrene butadiene rubber and 0.7 to 1.2 parts by weight of a thickener per 100 parts by weight of the graphite. It contained so as to be 1.3 to 2.4 parts by weight, the concentration of LiPF 6 in said non-aqueous electrolyte, Ri 0.6 to 1.05 mol / liter der, the average particle size of the graphite is 20 to a 30 [mu] m, and a specific surface area of 5 m 2 / g or less, said particulate modified styrene-butadiene rubber is comprised of core-shell particles, the core-shell particles, and wherein Rukoto contain acrylonitrile units in the core portion That relates to a non-aqueous electrolyte battery.
[0007]
In the absorption spectrum obtained by FT-IR measurement of the particulate modified styrene butadiene rubber, the absorption intensity based on the C≡N stretching vibration of the acrylonitrile unit is 0.1 to 0.1 of the absorption intensity based on the C = C stretching vibration of the butadiene unit. It is preferable that it is 2 times. Here, the absorption intensity refers to the height of the absorption peak viewed from the baseline of the spectrum.
The suitable range of the average particle diameter of the particulate modified styrene butadiene rubber is 0.05 to 0.4 μm.
The thickener is preferably carboxymethyl cellulose.
The concentration of LiPF 6 in the nonaqueous electrolyte is more preferably 0.7 to 0.9 mol / liter.
[0008]
The positive electrode includes 0.4 to 2 parts by weight of a particulate modified acrylic rubber per 100 parts by weight of the lithium-containing transition metal oxide, and the particulate modified acrylic rubber comprises a 2-ethylhexyl acrylate unit, an acrylic acid unit, and acrylonitrile. It preferably consists of a copolymer containing units.
In the absorption spectrum obtained by FT-IR measurement of the particulate modified acrylic rubber, the absorption intensity based on C = O stretching vibration of 2-ethylhexyl acrylate units and acrylic acid units is the absorption intensity based on C≡N stretching vibration of acrylonitrile units. It is preferably 3 to 50 times the strength.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The present invention uses a negative electrode containing a specific binder and a thickener in a specific ratio and a non-aqueous electrolyte having a low salt concentration, and further includes a positive electrode containing a specific binder in a specific ratio. By using together with the negative electrode and the non-aqueous electrolyte, it is characterized in that the high rate discharge characteristics, low-temperature characteristics, safety, etc. of the non-aqueous electrolyte battery are improved.
[0010]
The negative electrode is composed of, for example, a negative electrode mixture and a core material (current collector). The negative electrode mixture is prepared by blending a negative electrode active material, particulate modified styrene butadiene rubber, a thickener and the like at a predetermined ratio. The negative electrode can be obtained by, for example, coating or filling a negative electrode mixture on the surface of a metal foil such as copper foil or a core material such as punching metal, rolling, and cutting. From the viewpoint of reducing the size and weight of the battery, the thickness of the core is generally about 8 to 20 μm, and the thickness of the negative electrode is generally 80 to 200 μm.
[0011]
It is a negative electrode active substance, a carbon powder such as graphite. Of these, scaly graphite and spherical artificial graphite are preferably used. The average particle size of graphite is preferably 20 to 30 μm. Moreover, the specific surface area of graphite is 5 m < 2 > / g or less , for example, 4-5 m < 2 > / g.
[0012]
The particulate modified styrene butadiene rubber is a core-shell type particle , and the core portion of the core-shell type particle includes an acrylonitrile unit and has rubber elasticity. The core portion is obtained by sufficiently crosslinking a copolymer containing, for example, an acrylonitrile unit, a styrene unit, a butadiene unit, an acrylate unit, or the like with an appropriate crosslinking agent. The shell portion is made of a highly viscous polymer, for example, a copolymer containing acrylate units, styrene units, and the like.
[0013]
The core-shell type particles can be produced, for example, by a two-stage process in which a raw material monomer mixture in a core part containing a crosslinking agent is polymerized to produce a latex, and then a raw material monomer mixture in a shell part is grafted onto the latex particles. At this time, when acrylonitrile is contained in the raw material monomer of the core portion, a core portion having a high elastic modulus can be obtained.
[0014]
In the absorption spectrum obtained by FT-IR measurement, the particulate modified styrene butadiene rubber has an absorption intensity based on C≡N stretching vibration of acrylonitrile units of 0. It is preferable that the acrylonitrile unit and the butadiene unit are contained to the extent of 1 to 2 times. When the absorption strength based on the C≡N stretching vibration of the acrylonitrile unit is less than 0.1 times the absorption strength based on the C = C stretching vibration of the butadiene unit, sufficient strength can be obtained even if the particulate modified styrene butadiene rubber is included. The negative electrode cannot be obtained, or the surface of the active material is too covered with the particulate modified styrene butadiene rubber. On the other hand, when the absorption strength based on the C≡N stretching vibration of the acrylonitrile unit exceeds twice the absorption strength based on the C = C stretching vibration of the butadiene unit, the rubber elasticity of the binder is lowered, and the mixture is mixed with the core material. Becomes easy to peel.
[0015]
The average particle diameter of the particulate modified styrene butadiene rubber is preferably 0.05 to 0.4 μm because a sufficiently strong negative electrode can be obtained with a small amount of use. If the average particle size is too small, most of the surface of the active material is covered with the particulate modified styrene butadiene rubber, and if it is too large, the distance between the active material particles increases and the conductivity inside the negative electrode decreases. .
[0016]
An appropriate amount of the particulate modified styrene butadiene rubber in the negative electrode mixture is 0.6 to 1.7 parts by weight with respect to 100 parts by weight of the carbon material as the negative electrode active material. If the amount of the particulate modified styrene butadiene rubber is too small, a sufficiently strong negative electrode may not be obtained, and the mixture may be peeled off from the core material. The rate discharge characteristic becomes unsatisfactory.
In addition, in the case of conventional PVDF, the suitable compounding quantity in a negative electrode mixture is 5-10 weight part with respect to 100 weight part of negative electrode active materials, and is 2-5 weight part also in the case of SBR. Therefore, the content of the binder in the negative electrode mixture according to the present invention is remarkably reduced as compared with the conventional one.
[0017]
As the thickener used in the negative electrode mixture, for example, a cellulose thickener such as carboxymethylcellulose (CMC), a copolymer of ethylene and vinyl alcohol, or the like is used. These may be used alone or in combination of two or more. Of these, CMC is often used.
[0018]
The blending amount of the thickener in the negative electrode mixture is appropriately 0.7 to 1.2 parts by weight with respect to 100 parts by weight of the carbon material as the negative electrode active material. If the blending amount of the thickener is too small, a paste-like negative electrode mixture cannot be obtained and the mixture is easily peeled off from the core material. If it is too much, the active material is covered with the thickener, and the reaction The surface area is reduced.
[0019]
However, the total amount of the particulate modified styrene butadiene rubber and the thickener needs to be 1.3 to 2.4 parts by weight with respect to 100 parts by weight of the carbon material which is the negative electrode active material. If the total amount is less than 1.3 parts by weight, the active material particles cannot be sufficiently bonded to each other, and the strength of the negative electrode becomes insufficient. If the total amount is too large, the active material becomes a binder or a thickener. The reaction surface area becomes small.
[0020]
The positive electrode is made of, for example, a positive electrode mixture and a core material (current collector). The positive electrode mixture is prepared by blending a positive electrode active material, a conductive agent, a binder and the like at a predetermined ratio. The positive electrode can be obtained, for example, by coating or filling a positive electrode mixture on the surface of a metal foil such as an aluminum foil or a core material such as punching metal, rolling, and cutting. From the viewpoint of reducing the size and weight of the battery, the thickness of the core is generally about 8 to 20 μm, and the thickness of the positive electrode is generally 80 to 200 μm.
[0021]
Examples of the lithium-containing transition metal oxide that is the positive electrode active material include LiCoO 2 , LiNiO 2 , LiMn 2 O 4, and the like. These may be used alone or in combination of two or more.
[0022]
Examples of the conductive agent used for the positive electrode mixture include natural graphite such as flake graphite, artificial graphite such as vapor-grown graphite, and carbon black such as acetylene black. These may be used alone or in combination of two or more.
[0023]
As the binder used for the positive electrode mixture, particulate modified acrylic rubber, PVDF, or the like can be used, but particulate modified acrylic rubber is preferably used. The particulate modified acrylic rubber can be obtained as a dispersion using water or an organic solvent as a dispersion medium, but a dispersion using an organic solvent as a dispersion medium is preferred. Further, it is preferable that the particulate modified acrylic rubber has an average particle diameter of 0.05 to 0.3 μm because a positive electrode having a good balance of binding force, active material density, and porosity can be obtained.
[0024]
The blending amount of the particulate modified acrylic rubber in the positive electrode mixture is preferably 0.4 to 2 parts by weight with respect to 100 parts by weight of the positive electrode active material. If the blending amount of the particulate modified acrylic rubber is too small, a positive electrode with sufficient strength may not be obtained, and the mixture may be peeled off from the core material. If it is too large, the porosity of the positive electrode becomes small and the active material becomes small. The reaction surface area becomes smaller and the high rate discharge characteristics become worse.
[0025]
In the non-aqueous electrolyte battery of the present invention, when particulate modified acrylic rubber is used as the binder of the positive electrode mixture, both the affinity between the negative electrode and the non-aqueous electrolyte and the affinity between the positive electrode and the non-aqueous electrolyte are suitable. Since the balance is also excellent, the distribution of the nonaqueous electrolyte in the battery becomes uniform, and a battery having particularly excellent low-temperature characteristics and high-rate discharge characteristics can be obtained.
[0026]
The affinity between the electrode and the nonaqueous electrolyte can be evaluated by the contact angle between the surface of the electrode and the nonaqueous electrolyte (nonaqueous electrolyte). The value of the contact angle varies depending on the type of the nonaqueous electrolyte, the active material density, etc., but 10 to 30 ° is a preferable range. If the contact angle is too low, the electrode absorbs too much non-aqueous electrolyte, resulting in insufficient high-rate discharge characteristics of the battery. If the contact angle is too large, the electrode hardly absorbs non-aqueous electrolyte. The rate discharge characteristics deteriorate.
[0027]
The particulate modified acrylic rubber is preferably made of a copolymer containing a 2-ethylhexyl acrylate unit, an acrylic acid unit, and an acrylonitrile unit. Further, in the absorption spectrum obtained by the FT-IR measurement, the absorption intensity based on C═O stretching vibration of 2-ethylhexyl acrylate units and acrylic acid units is 3 to 3 of the absorption intensity based on C≡N stretching vibration of acrylonitrile units. It is preferably 50 times. When the absorption strength based on the C═O stretching vibration is less than 3 times the absorption strength based on the C≡N stretching vibration, the binding force of the particulate modified acrylic rubber is reduced. The rubber elasticity of the acrylic rubber becomes insufficient, and the strength of the positive electrode mixture becomes weak.
[0028]
In the FT-IR measurement, the absorption spectra of the particulate modified styrene butadiene rubber and the particulate modified acrylic rubber are measured using, for example, those obtained by coating the particulate modified styrene butadiene rubber and the particulate modified acrylic rubber on a KBr plate, respectively. That's fine. Here, in general, absorption based on C═C stretching vibration of butadiene units is observed in the vicinity of 880 to 940 cm −1 , and absorption based on C═O stretching vibration of 2-ethylhexyl acrylate units and acrylic acid units is 1700 to 1760 cm. The absorption based on the C≡N stretching vibration of the acrylonitrile unit is observed in the vicinity of −1 to 2280 cm −1 .
[0029]
If the positive electrode and the negative electrode are laminated with a separator interposed therebetween, an electrode plate group can be obtained. The electrode plate group may be further wound. As the separator, a polyethylene microporous film or the like is used, and the thickness is generally 10 to 40 μm. When obtaining a prismatic battery, the wound electrode plate group is compressed from one direction so that the cross section becomes substantially elliptical.
[0030]
FIG. 1 shows a cross-sectional view of a prismatic battery, which is an example of the nonaqueous electrolyte battery of the present invention, cut along a plane parallel to the winding direction of the electrode plate group. In the figure, reference numeral 1 denotes a rectangular battery case, in which an electrode plate group is filled. The electrode plate group is obtained by laminating a sheet-like positive electrode plate 2 and a sheet-like negative electrode plate 3 with a separator 4 interposed therebetween, winding and further compressing to a certain flatness.
[0031]
As the non-aqueous solvent used for the non-aqueous electrolyte, a non-aqueous solvent conventionally used in lithium ion secondary batteries and the like can be used without particular limitation. Examples of such include ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and propylene carbonate. These may be used alone or in combination of two or more.
[0032]
The concentration of LiPF 6 in the nonaqueous electrolyte is 0.6 to 1.05 mol / liter. When the concentration of LiPF 6 is less than 0.6 mol / liter, the function of the battery is impaired, and when it exceeds 1.05 mol / liter, the safety of the battery is impaired. In order to obtain a non-aqueous electrolyte battery that is excellent in high-rate discharge characteristics and low-temperature characteristics and has particularly high safety, the concentration of LiPF 6 is preferably 0.7 to 0.9 mol / liter.
[0033]
【Example】
Next, the present invention will be specifically described based on examples and comparative examples. However, the present invention is not limited to the following examples .
[0034]
"Examples 1-9 and Comparative Examples 1-10"
Batteries A to S were produced as shown below, and their characteristics were evaluated.
[0035]
Production of Negative Electrode Using a predetermined binder, a negative electrode mixture having a predetermined composition used for batteries A to S was prepared. As the negative electrode active material, scaly graphite was used, as the thickener, carboxymethylcellulose (CMC) was used, and as the binder, those shown in Table 1 were used. Moreover, the compounding quantity of the binder and the thickener with respect to 100 parts by weight of the active material in the negative electrode mixture and the total of both are shown in Table 1 in parts by weight.
[0036]
[Table 1]
The binder shown in Table 1 will be described below.
BM400B: particulate modified styrene butadiene rubber manufactured by Nippon Zeon Co., Ltd. Average particle size 0.2 μm. In the absorption spectrum obtained by the FT-IR measurement, the absorption intensity based on the C≡N stretching vibration of the acrylonitrile unit is 0.5 times the absorption intensity based on the C = C stretching vibration of the butadiene unit.
[0038]
The absorption spectrum is shown in FIG. The measurement conditions are a sample scan count of 32, a background scan count of 32, a resolution of 4000, and a sample gain of 1.0. The measurement apparatus uses a microscopic FT-IR (Continuum (manufactured by Nicolet), light source: AVATAR-360). It was.
[0039]
As a sample for measurement, a solution obtained by dissolving a binder in N-methylpyrrolidone was applied on a KBr plate and dried. In FIG. 2, the absorption peak observed near 2237 cm −1 is based on the C≡N stretching vibration of the acrylonitrile unit, and the absorption peak observed near 911 cm −1 is based on the C═C stretching vibration of the butadiene unit. is there.
[0040]
MPE: Modified polyethylene resin.
SBR: Styrene butadiene rubber.
PVDF: polyvinylidene difluoride.
[0041]
For comparison, a transmission spectrum obtained by FT-IR measurement of SBR is shown in FIG. The measurement conditions, measurement apparatus, and the like are the same as in FIG. In FIG. 3, an absorption peak based on C≡N stretching vibration of acrylonitrile units is not observed near 2237 cm −1 .
[0042]
The obtained negative electrode mixture composed of an active material, a binder and a thickener was applied to both sides of a copper foil core material having a thickness of 15 μm, rolled to a thickness of 140 μm, cut into a predetermined length, A negative electrode was obtained. A negative electrode lead made of the same material as the core material was connected to the negative electrode.
[0043]
Production of positive electrode 4 parts by weight of PVDF as a binder and 3 parts by weight of acetylene black as a conductive agent were blended with 100 parts by weight of LiCoO 2 to obtain a positive electrode mixture. Next, the obtained positive electrode mixture was applied to both surfaces of a 20 μm thick aluminum foil core, rolled to a predetermined thickness, cut into a predetermined length, and a positive electrode was obtained. A positive electrode lead made of the same material as the core material was connected to the positive electrode.
[0044]
Production of Battery The obtained positive electrode and negative electrode were laminated with a separator interposed therebetween, and wound to obtain an electrode plate group. As the separator, a polyethylene microporous film having a thickness of 27 μm was used. The wound electrode plate group was compressed from one direction so that the cross section was substantially elliptical.
[0045]
A nonaqueous electrolyte in which LiPF 6 was dissolved in a mixture of an equal volume of ethylene carbonate and ethyl methyl carbonate as a nonaqueous solvent so as to have a salt concentration (M: mol / liter) shown in Table 1 was prepared.
[0046]
The electrode plate group was accommodated together with 3.2 g of a non-aqueous electrolyte in a predetermined aluminum case with insulating rings arranged on the top and bottom. And after connecting a negative electrode lead and a positive electrode lead to a predetermined location, the opening part of the case was sealed with the sealing board, and the nonaqueous electrolyte battery AS was completed. These batteries are rectangular with a width of 30 mm, a height of 48 mm, and a thickness of 5 mm, and the nominal capacity of the battery is 600 mAh.
[0047]
Next, the evaluation content of the obtained nonaqueous electrolyte battery will be described.
The non-aqueous electrolyte batteries A to S having low temperature characteristics were charged in an atmosphere of 0 ° C. at 600 mA until the battery voltage reached 4.2 V, and the charge capacity at this time was examined. The results are shown in Table 1.
[0048]
The high-rate discharge characteristics nonaqueous electrolyte batteries A to S were charged at 600 mA until the battery voltage reached 4.2 V, and discharged at 120 mA until the battery voltage reached 3 V. Next, the battery was charged at 600 mA until the battery voltage was 4.2 V, and discharged at 1200 mA until the battery voltage was 3 V. In each case, the discharge capacity was determined, and the ratio of the latter to the former (capacity ratio) was determined. The results are shown in Table 1 in terms of 100 minutes.
[0049]
Regarding the obtained nonaqueous electrolyte batteries A to S, the operation of charging at 600 mA until the battery voltage reached 4.2 V, and discharging until the battery voltage reached 3 V at 600 mA was repeated 200 times. Then, the ratio of the 200th discharge capacity to the first discharge capacity was determined. The results are shown in Table 1 in terms of 100 minutes.
[0050]
Overcharge test (safety test)
Regarding the obtained nonaqueous electrolyte batteries A to S, the battery was continuously charged at 1260 mA, and charging was stopped when the surface temperature of the battery reached 80 ° C. After that, the battery was left for a while, the battery whose surface temperature reached 90 ° C. or higher was rated as x, and the battery whose temperature was lower than 90 ° C. was marked as ◯. The results are shown in Table 1. It can be said that a battery with an evaluation of “◯” has high safety.
[0051]
From the results in Table 1, the following can be understood.
Among batteries salt concentration in the non-aqueous electrolyte is 0.6 to 1.05 mol / l, the battery of the embodiment uses a particulate modified styrene-butadiene rubber negative electrode mixture are all that is highly safe I understand. On the other hand, the battery A of Comparative Example in which the salt concentration in the nonaqueous electrolyte is 1.1 mol / liter is insufficient in safety. In addition, the battery S of the comparative example in which the salt concentration in the nonaqueous electrolyte is 0.55 mol / liter is insufficient in low temperature characteristics, high rate discharge characteristics, and capacity maintenance rate.
[0052]
The batteries D to F of Comparative Examples that do not use the particulate modified styrene butadiene rubber as the negative electrode mixture are insufficient in safety, low temperature characteristics, and the like. In addition, the battery F using PVDF, which has been widely used in the past, as the binder of the negative electrode mixture, is used when the electrode plate group is manufactured even though the amount of the binder is larger than that of other batteries. The strength of the electrode plate was insufficient, such as cracks in the electrode plate.
[0053]
Table 1 shows that the blending amount of the particulate modified styrene butadiene rubber is preferably 0.6 to 1.7 parts by weight with respect to 100 parts by weight of the active material. Battery H with a binder content of 0.5 part by weight could not be evaluated because it was difficult to produce a negative electrode. Further, the battery R having a binder content of 1.8 parts by weight is insufficient in high rate discharge characteristics and capacity retention.
[0054]
Table 1 also shows that the blending amount of the thickener is preferably 0.7 to 1.2 parts by weight with respect to 100 parts by weight of the active material. Battery Q with a thickener compounding amount of 0.7 part by weight could not be evaluated because it was difficult to produce a negative electrode. In addition, the battery K having a binder content of 1.3 parts by weight is insufficient in high rate discharge characteristics and capacity retention.
[0055]
Table 1 further shows that the total amount of the particulate modified styrene butadiene rubber and the thickener is preferably 1.3 to 2.4 parts by weight with respect to 100 parts by weight of the active material. Batteries O and R having a total blending amount of 2.5 parts by weight or more are insufficient in high rate discharge characteristics and capacity retention.
[0056]
<< Example 10 >>
Obtained for LiCoO 2 of 100 parts by weight, except that blended BM700H 0.27 parts by weight BM500B and thickener 0.53 parts by weight as a binder, a positive electrode mixture in the same manner as in Example 2 It was. Then, using the obtained positive electrode mixture was produced in the same manner as the battery T of Example 2 was evaluated in the same manner. The results are shown in Table 1.
[0057]
The binder and thickener used are described below.
BM500B: A particulate modified acrylic rubber manufactured by Nippon Zeon Co., Ltd. In the absorption spectrum obtained by the FT-IR measurement, the absorption peak intensity based on the C═O stretching vibration of the 2-ethylhexyl acrylate unit and the acrylic acid unit is about 10 of the absorption peak intensity based on the C≡N stretching vibration of the acrylonitrile unit. Is double. The spectrum is shown in FIG.
[0058]
The measurement conditions, measurement apparatus, and the like are the same as in the case of FIG. In FIG. 4, the absorption peak observed in the vicinity of 2240 cm −1 is based on the C≡N stretching vibration of the acrylonitrile unit, and the absorption peak observed in the vicinity of 1733 cm −1 is the C = This is based on O stretching vibration.
[0059]
BM700H: a copolymer containing ethylene units and vinyl alcohol units manufactured by Nippon Zeon Co., Ltd. The transmission spectrum obtained by the FT-IR measurement is shown in FIG. The measurement conditions, measurement apparatus, etc. are the same as in the case of FIG. In FIG. 5, the two types of absorption peaks observed near 2852 cm −1 and 2930 cm −1 are based on OH groups of vinyl alcohol units bonded to ethylene units.
[0060]
As shown in Table 1, the results of the evaluation, the low-temperature characteristics, high-rate discharge characteristics and capacity retention rate of the battery T are both higher than the batteries of Examples 1 to 9 had excellent safety. From this, it can be seen that various characteristics of the battery are remarkably improved by using the particulate modified acrylic rubber as the binder for the positive electrode.
[0061]
【The invention's effect】
According to the present invention, it is possible to obtain a non-aqueous electrolyte battery that is excellent in high-rate discharge characteristics and low-temperature characteristics and has high safety.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a prismatic battery which is an example of a nonaqueous electrolyte battery of the present invention.
FIG. 2 is an example of an absorption spectrum obtained by FT-IR measurement of particulate modified styrene butadiene rubber.
[Fig. 3]
It is an example of the transmission spectrum obtained by FT-IR measurement of SBR.
[Fig. 4]
It is an example of the absorption spectrum obtained by FT-IR measurement of particulate modified acrylic rubber.
[Figure 5]
It is an example of the transmission spectrum obtained by the FT-IR measurement of the copolymer containing an ethylene unit and a vinyl alcohol unit.
[Explanation of symbols]
1 Battery Case 2 Positive Plate 3 Negative Plate 4 Separator
Claims (5)
前記負極が、前記黒鉛１００重量部あたり０．６〜１．７重量部の粒子状変性スチレンブタジエンゴムおよび０．７〜１．２重量部の増粘剤を両者の合計量が１．３〜２．４重量部になるように含有し、
前記非水電解質におけるＬｉＰＦ6の濃度が、０．６〜１．０５モル／リットルであり、
前記黒鉛の平均粒径が２０〜３０μｍであり、比表面積が５ｍ 2 ／ｇ以下であり、
前記粒子状変性スチレンブタジエンゴムが、コアシェル型粒子からなり、前記コアシェル型粒子は、コア部分にアクリロニトリル単位を含んでいることを特徴とする非水電解質電池。A non-aqueous electrolyte battery comprising a positive electrode made of a lithium-containing transition metal oxide, a negative electrode made of graphite , a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte in which LiPF 6 is dissolved in a non-aqueous solvent,
The negative electrode is composed of 0.6 to 1.7 parts by weight of particulate modified styrene butadiene rubber and 0.7 to 1.2 parts by weight of a thickener per 100 parts by weight of graphite. Contained in an amount of 2.4 parts by weight,
The concentration of LiPF 6 in the non-aqueous electrolyte is 0.6 to 1.05 mol / liter,
The graphite has an average particle size of 20 to 30 μm, a specific surface area of 5 m 2 / g or less,
It said particulate modified styrene-butadiene rubber is comprised of core-shell particles, the core-shell particles, a non-aqueous electrolyte battery according to claim Rukoto contain acrylonitrile units in the core portion.
Priority Applications (13)
| Application Number | Priority Date | Filing Date | Title |
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| JP2000267626A JP3615472B2 (en) | 2000-09-04 | 2000-09-04 | Non-aqueous electrolyte battery |
| US09/845,265 US6773838B2 (en) | 2000-09-04 | 2001-05-01 | Non-aqueous electrolyte secondary battery and negative electrode for the same |
| DE60134432T DE60134432D1 (en) | 2000-09-04 | 2001-05-14 | Nonaqueous electrolyte secondary battery and negative electrode therefor |
| EP20040018679 EP1478039B1 (en) | 2000-09-04 | 2001-05-14 | Non-aqueous electrolyte secondary battery and negative electrode for the same |
| DE2001629482 DE60129482T2 (en) | 2000-09-04 | 2001-05-14 | Non-aqueous electrolyte secondary battery and negative electrode for it |
| EP20040077458 EP1492182B1 (en) | 2000-09-04 | 2001-05-14 | Non-aqueous electrolyte secondary battery and negative electrode for the same |
| DE2001630296 DE60130296T2 (en) | 2000-09-04 | 2001-05-14 | Nonaqueous electrolyte secondary battery and negative electrode therefor |
| EP20010304270 EP1184921B1 (en) | 2000-09-04 | 2001-05-14 | Non-aqueous electrolyte secondary battery and negative electrode for the same |
| CNB2004100699578A CN1249834C (en) | 2000-09-04 | 2001-06-04 | Non-aqueous electrolyte secondary battery |
| CNB2004100699563A CN1253955C (en) | 2000-09-04 | 2001-06-04 | Non-aqueous electrolyte secondary battery and negative electrode for the same |
| CNB011211687A CN1233056C (en) | 2000-09-04 | 2001-06-04 | Nonaqueous electrolyte secondary battery and negative electrode for nonaqueous electrolyte secondary battery |
| US10/883,727 US7147964B2 (en) | 2000-09-04 | 2004-07-06 | Non-aqueous electrolyte secondary battery and negative electrode for the same |
| US10/943,839 US7150937B2 (en) | 2000-09-04 | 2004-09-20 | Non-aqueous electrolyte secondary battery and negative electrode for the same |
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| JP4535761B2 (en) * | 2004-03-30 | 2010-09-01 | 三洋電機株式会社 | Nonaqueous electrolyte secondary battery |
| JP2005294028A (en) * | 2004-03-31 | 2005-10-20 | Mitsubishi Heavy Ind Ltd | Lithium secondary battery |
| JP5126802B2 (en) * | 2004-06-07 | 2013-01-23 | パナソニック株式会社 | Method for producing positive electrode plate for non-aqueous secondary battery |
| JP2006092760A (en) * | 2004-09-21 | 2006-04-06 | Matsushita Electric Ind Co Ltd | Method of manufacturing negative electrode plate for nonaqueous secondary battery |
| JP4852836B2 (en) * | 2004-10-05 | 2012-01-11 | パナソニック株式会社 | Method for producing electrode plate for negative electrode of non-aqueous secondary battery |
| KR100686849B1 (en) | 2005-03-24 | 2007-02-26 | 삼성에스디아이 주식회사 | Lithium secondary battery |
| CN101156264B (en) * | 2005-04-07 | 2011-05-25 | Lg化学株式会社 | Binder with good rate property and long cycleability for lithium secondary battery |
| WO2010098380A1 (en) * | 2009-02-25 | 2010-09-02 | 日本ゼオン株式会社 | Electrode for lithium-ion secondary cell |
| JP5879673B2 (en) | 2009-09-03 | 2016-03-08 | ソニー株式会社 | Method for producing negative electrode for non-aqueous electrolyte secondary battery |
| JP5765228B2 (en) * | 2009-09-30 | 2015-08-19 | 日本ゼオン株式会社 | Porous membrane for secondary battery and secondary battery |
| JPWO2011080884A1 (en) * | 2009-12-28 | 2013-05-09 | パナソニック株式会社 | Anode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery |
| EP3147972B1 (en) * | 2014-05-20 | 2018-09-05 | Zeon Corporation | Composite particles for electrochemical device electrode and method for manufacturing composite particles for electrochemical device electrode |
| WO2017051470A1 (en) | 2015-09-25 | 2017-03-30 | 株式会社東芝 | Electrode for non-aqueous electrolyte battery, non-aqueous electrolyte battery, and battery pack |
| JP6964421B2 (en) * | 2017-03-23 | 2021-11-10 | ローム株式会社 | Semiconductor light emitting device |
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| JPH11111300A (en) * | 1997-09-30 | 1999-04-23 | Sanyo Electric Co Ltd | Negative electrode for nonaqueous secondary battery |
| JPH11288718A (en) * | 1998-04-01 | 1999-10-19 | Toyota Central Res & Dev Lab Inc | Nonaqueous solvent secondary battery |
| JP4482953B2 (en) * | 1998-06-09 | 2010-06-16 | パナソニック株式会社 | Anode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery using the same |
| JP2000228224A (en) * | 1999-02-09 | 2000-08-15 | Toyota Central Res & Dev Lab Inc | Nonaqueous electrolyte secondary battery |
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