JP3579598B2 - Method for producing slurry for lithium secondary battery electrode - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、リチウム２次電池電極用スラリーの製造方法に関するものであり、特には最初に結着材を分散媒に分散させて結着材溶液を調製し、可塑剤、電極活物質、導電材及び必要に応じ前記結着材溶液の一部を、好ましくは３軸遊星型ミキサーを用いて、混練してペーストを得、調製した結着材溶液もしくはその未使用部分を添加し、好ましくは３軸遊星型ミキサーを用いて、混練しスラリーを得ることを特徴とするリチウム２次電池電極用スラリーの製造方法に関する。
【０００２】
【従来の技術】
リチウム２次電池の基本構成は、正極及び負極並びに両電極に介在せしめられる電解質を保持したセパレータである。
このうち、正極及び負極は、活物質、導電材、結着材に必要に応じて可塑剤を分散媒に混合分散して成るスラリーを金属箔、金属メッシュ等の集電体に塗工したものを使用する。
正極活物質としては遷移金属のリチウム酸化物が最適である。たとえば、マンガン酸リチウム（ＬｉＭｎ２ Ｏ４ ）、コバルト酸リチウム（ＬｉＣｏＯ２ ）、ニッケル酸リチウム（ＬｉＮｉＯ２ ）等が好ましい。また、負極活物質としてはリチウムイオンを吸蔵・放出できる公知の物質であり、たとえばリチウムイオン吸蔵能を示す炭素材料が好ましい。炭素材料の中でもコークス系炭素、黒鉛系炭素がより好ましい。
導電材としては電子伝導性の公知の物質であり、たとえば天然黒鉛、カーボンブラック、アセチレンブラック等が好ましく、これらの混合物も使用できる。
結着材としてはフッ素系樹脂が良好で、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）、ヘキサフロロプロピレン（ＨＦＰ）等が好ましく、これらの共重合体も使用できる。
分散媒としては、結着材が溶解可能な有機溶媒が適切で、たとえばアセトン、メチルエチルケトン（ＭＥＫ）、テトラヒドロフラン（ＴＨＦ）、ジメチルホルムアミド、ジメチルアセタミド、テトラメチル尿素、リン酸トリメチル、Ｎ−メチルピロリゾン（ＮＭＰ）等が好ましい。
また、必要に応じて加える可塑剤は成膜後に電解液と置換可能な有機溶媒が適切で、フタル酸ジエステル類が好ましい。
集電体にはステンレス鋼、ニッケル、アルミニウム、チタン、銅のパンチングメタル、エキスパンドメタルが好ましく、表面処理を施した材料も使用できる。電解質は一般に溶媒とその溶媒に溶解するリチウム塩とから構成される。溶媒としてはポリエチレンカーボネート、エチレンカーボネート、ジメチルスルホキシド、ブチルラクトン、スルホラン、１，２−ジメトキシエタン、テトラヒドロフラン、ジエチルカーボネート、メチルエチルカーボネート、ジメチルカーボネート等の有機溶媒が挙げられ、これらの一種又は二種以上を混合して使用するのが好ましい。リチウム塩としては、ＬｉＣＦ３ ＳＯ３ 、ＬｉＡｓＦ６ 、ＬｉＣｌＯ４ 、ＬｉＢＦ４ 、ＬｉＰＦ６ 等が好ましい。
【０００３】
塗工に必要なスラリーは、上記活物質、導電材、結着材、分散媒および可塑剤を所定の比率で混練して調製する。調製には、ホモジナイザー、ボールミル、サンドミル、ロールミル、遊星型混練機等の混練分散機が用いられる。また、集電体への塗工には、グラビアコート、ブレードコート、コンマコート、ディップコート等の各塗工方法が用いられる。
【０００４】
スラリーの調製は、各材料を同時に投入し混練する方法があるが、粉体材料の比重差から均一な混練が困難なこともあり、分散媒を２回に分けて混練する方法が取られている（特開平９−１２９２２２）。この方法では、初めの混練においては、比重差の大きい粉体材料の均一な混練を目的として、少量の分散媒によるペースト化が行われる。２度目の混練においては分散媒の均一な分散を目的とする。
【０００５】
【発明が解決しようとする課題】
しかしながら、このように分散媒を分割した混練を行なっても、均一なスラリーを安定して得ることは困難であった。集電体へ塗工すべきスラリーが不安定であると、塗工条件が一定にならずに塗工膜の特性が安定しないため、電池特性に影響を与え、電池の安定生産に支障をきたすことになる。
また、一旦、スラリーを調製すると、均一性を保つ間にその全量を速やかに使い切らねばならないので、スラリー量の管理も難しかった。
本発明は上記の欠点を解決し、安定して均一な電極用スラリーを得ることを課題とする。本発明のまた別の課題は、必要量のスラリーを必要時に得るようにすることである。
【０００６】
【課題を解決するための手段】
そこで、発明者らはスラリーの不均質を招く要因として、結着材の分散媒への溶解不良や粉体に付着している気体の除去不良に着目した。また、最初にスラリーの製造方法としては、結着材を分散媒に分散させ結着材溶液を調製し、可塑剤、電極活物質、導電材及び必要に応じ前記結着材溶液の一部を混練してファニキュラー域に対応するペーストを得、それに結着材溶液を添加して混練しスラリーを得るのが有用であることを見いだした。
【０００７】
かくして、本発明は、正極と、負極と、前記正極と負極との間に介在せしめられるセパレータと、電解液とから構成されるリチウム２次電池の前記正極及び負極の電極用スラリーの製造方法において、
結着材を分散媒に分散させて結着材溶液を調製する工程、
可塑剤、電極活物質、導電材及び必要に応じ前記結着材溶液の一部を混練してファニキュラー域に対応するペーストを得る工程、及び
前記ペーストに前記調製した結着材溶液もしくはその未使用部分を添加し、混練してスラリーを得る工程
を包含することを特徴とするリチウム２次電池電極用スラリーの製造方法を提供するものである。
【０００８】
より具体的には、本発明は、正極と、負極と、前記正極と負極との間に介在せしめられるセパレータと、電解液とから構成されるリチウム２次電池の前記正極及び負極の電極用スラリーの製造方法において、
結着材を分散媒に分散させて結着材溶液を調製する工程、
可塑剤、電極活物質、導電材及び必要に応じ前記結着材溶液の一部を３軸遊星型ミキサーを用いて混練してファニキュラー域に対応するペーストを得る工程、及び
前記ペーストに前記調製した結着材溶液もしくはその未使用部分を添加し、好ましくは３軸遊星型ミキサーを用いて混練してスラリーを得る工程
を包含することを特徴とするリチウム２次電池電極用スラリーの製造方法を提供する。
【０００９】
前記結着材溶液を添加して混練しスラリーを得る工程において、大気圧以下、分散媒の蒸気圧以上の圧力下で処理することが好ましい。
電極活物質、導電材、可塑剤及び必要に応じて結着材溶液の一部を混練して得たペーストを保管し、必要時に結着材溶液を添加して混練しスラリーを得ることができる。
【００１０】
ここで、「ファニキュラー域」とは、固−液系の充填状態でいえば、固相、液相とも連続で気相が不連続である状態を云う。
【００１１】
【発明の実施の形態】
図１は、本発明の代表的な製造フローシートを示す。
結着材を分散媒に分散させて結着材溶液を調製する工程は、結着材の溶解不良を解決する手段として有効である。結着材の溶解に有効な分散媒を選択し、分散混練機を用いて溶解する。フッ素系樹脂である結着材を溶解する分散媒としては、アセトン、ＭＥＫ、ＮＭＰがあるが、取り扱いの容易さ、価格、毒性等からアセトンが好ましい。分散混練機には、例えば、ホモジナイザー、ボールミル、サンドミル、ロールミル、遊星型混練機がある。溶媒分散は結着材の未溶解部が残らないように注意する。分散時間は１０〜１２０分で、好ましくは２０〜４０分である。
【００１２】次に、可塑剤、電極活物質、導電材及び必要に応じ前記結着材溶液の一部を混練してペーストを得る。これは、粉体材料である電極活物質と導電材との比重差が大きいことから、粉体材料の均一な混練のため有効である。必要な液体量は粉体全体を濡らす程度で十分で、固−液系の充填状態でいえば、固相、液相とも連続で気相が不連続であるファニキュラー域に対応する。したがって、液体量は粉体の粒度分布や液体系との親和力等で異なり、結着材を用いずに可塑剤のみで十分である場合もある。混練機には、例えば、ホモジナイザー、ボールミル、サンドミル、ロールミル、遊星型混練機がある。粘度が一定したスラリーを安定して製造できる等の点から３軸遊星型混練機が最も好ましい。混練時間は装置により差があるが、おおむね１０〜１２０分で、好ましくは２０〜４０分である。
【００１３】
３軸遊星型混練機は、遊星運動を行う２枚のブレードと高速回転翼の３軸から構成される。２枚のブレードは自転及び公転し、この自公転に同期しながら高速回転翼は自転する構造をとる。これにより容器内ではデッドスペースのない混練が可能となる。また、比重差の大きい粉体や粒度の異なる粉体の混合も容易に行える。
【００１４】
次に、上記で得られたペーストに、上記調製された結着剤溶液もしくは上記ペーストを得る工程で未使用の結着材溶液を添加して混練する。この工程においては、大気圧以下、分散媒の蒸気圧以上の圧力下で処理することが重要である。粉体中に含まれる気体は、分散媒と粉体との濡れを阻害するものであり、均一なスラリーを製造する上で十分除去すべきものである。この処理により固−液系の充填状態でいえば、固相は不連続、液相は連続で、気相は零である理想的なスラリー域が可能となる。気体の除去には真空処理が有効であるが、分散媒が低沸点溶媒である場合、真空での沸騰蒸発が問題となる。そこで、低沸点溶媒の蒸気圧以上にすることで溶媒の減少を回避し、かつ、大気圧より低圧とすることで粉体に付着している気体を除去するものである。
結着材であるフッ素系樹脂を溶解できる有機溶媒として、アセトン、ＭＥＫが有効であるが、その蒸気圧は２５℃でそれぞれ２３１ｍｍＨｇ、９０ｍｍＨｇであり、３０℃ではそれぞれ２８５ｍｍＨｇ、１１５ｍｍＨｇとなる。したがって、使用する有機溶媒に応じた容器内の圧力調整が必要となる。たとえばアセトンを使用した混練であれば、容器内の圧力は３００ｍｍＨｇ程度が好ましく、ＭＥＫであれば１５０ｍｍＨｇ程度が好ましい。この圧力調整により均一なスラリーを安定して製造できる。
また、混練時の材料温度は混練装置の撹拌熱等で室温より高温になるため、容器の冷却は必要である。冷却は水冷が最適である。
【００１５】ペーストは密閉容器内に保管することが可能である。したがって、少量の塗工であれば、保管したペーストを必要時に必要量だけ取りだして結着剤溶液を添加してスラリー化して分散することで対応でき、工程省略による経済効果が期待できる。
【００１６】
【実施例】
以下、実施例及び比較例に基づいて、本発明を詳しく説明する。
【００１７】
（実施例１及び比較例１：正極スラリーの製造に当っての混練方法の違い）
（ａ）材料の秤量
電極活物質にはマンガン酸リチウム（ＬｉＭｎ２ Ｏ４ ）、導電剤には人造黒鉛、結着剤にはポリフッ化ビニリデン（ＰＶＤＦ）、可塑剤にはフタル酸ジブチル（ＤＢＰ）を材料として、２次電池正極用スラリーを調製した。組成は、電極活物質５６重量％、導電剤６重量％、結着剤１５重量％、可塑剤２３重量％とした。分散媒にはアセトンを使用し、電極活物質１重量部に対して１．６４重量部とした。
（ｂ）結着材の分散媒への溶解
溶解はホモディスパーを用いて行った。分散時間は３０分とした。得られた結着材溶液は透明で未溶解部は観察されなかった。
（ｃ）ペーストの調製
可塑剤に活物質、導電材を投入し、さらに結着材溶液を全溶液の２０重量部を投入して混練を行った。混練は３軸遊星型ミキサーを用いて３０分行った。得られたペーストは「べとべと」状態であり、固−液系の充填状態でいえば、固相、液相とも連続で気相が不連続であるファニキュラー域に対応した。
（ｄ）スラリーの調製
得られたペーストに残りの結着材溶液を投入してさらに混練を行った。混練は３軸遊星型ミキサーを用いて３０分行った。混練時は水冷による容器内の冷却を行い、表１に示す圧力で処理した。
【００１８】（ｅ）スラリー評価
得られたスラリーは円筒型粘度計（剪断速度４８／ｓ）で粘度を測定し、ｇａｐ５００ｕｍのアプリケーターで成膜した。得られた膜で引っ張り強度試験を行い、破断強度と破断時の伸びを測定した。結果を表１に示した。
比較例として、結着材を分散媒に溶解せずに材料を同時に混練したボールミルの場合と結着材を分散媒に溶解した後、オスターブレンダーで混練した場合の結果を併記した。ともに混練は大気圧（７６０ｔｏｒｒ）下で行った。
【００１９】
【表１】
表１から次のことが判る：
（１）ボールミルとブレンダーを比較すると、結着剤を分散媒に溶解したブレンダーの方が低粘度である。
（２）実施例と比較例を比べると、ファニキュラー域のペーストを介在させた実施例の方が低粘度である。
（３）アセトンの蒸気圧を考慮した実施例（３００ｔｏｒｒ）がもっとも粘度が低い。
以上のことから、結着剤を分散媒に溶解すること、ファニキュラー域のペーストを作製してからスラリー化すること、スラリー化に当っては分散媒の蒸気圧を考慮することによって、分散媒が同じ量であってもスラリーの粘度を下げることができた。したがって、本発明による製造方法が従来の方法であるボールミルやブレンダーを用いるよりアセトン量を削減できることが判る。
【００２１】
（実施例２及び比較例２：正極スラリーの製造に当ってのアセトン量の削減効果）
（ａ）材料の秤量
アセトン量の削減効果を２次電池正極用スラリーで調査した。電極活物質にはコバルト酸リチウム（ＬｉＣｏＯ２ ）、導電剤には人造黒鉛、結着剤にはポリフッ化ビニリデン（ＰＶＤＦ）、可塑剤にはフタル酸ジブチル（ＤＢＰ）を材料とした。組成は、電極活物質７０重量％、導電剤５重量％、結着剤８重量％、可塑剤１７重量％とした。
（ｂ）ペーストを介在させない製造方法
分散媒であるアセトンは電極活物質１重量部に対して１．４１重量部とした。結着剤はホモディスパーを用いて分散媒に溶解した。分散時間は３０分で、得られた結着材溶液は透明で未溶解部は観察されなかった。
この結着剤溶液に、可塑剤、活物質、導電剤を同時に投入し、３軸遊星型ミキサーで３０分間混練した。混練時の圧力は３００ｔｏｒｒとした。得られたスラリーを円筒型粘度計で粘度を測定したところ、１．９５Ｐａ・ｓであった。
（ｃ）ペーストを介在させる製造方法
実施例１と同様にペーストを介在させる製造方法を試み、アセトン量の削減効果を把握した。
分散媒であるアセトンは電極活物質１重量部に対して０．５９重量部とした。結着剤はホモディスパーを用いて分散媒に溶解した。分散時間は３０分で、得られた結着材溶液は透明で未溶解部は観察されなかった。
可塑剤に活物質、導電材を投入し、さらに結着材溶液を全溶液の５０重量部を投入して混練を行った。混練は３軸遊星型ミキサーで３０分行い、ファニキュラー域に対応するペーストを得た。
得られたペーストに残りの結着材溶液を投入し、３軸遊星型ミキサーで３０分混練した。圧力は３００ｔｏｒｒとした。
得られたスラリーに分散媒であるアセトンを徐々に加え、混練を継続しながらスラリー粘度を上記のペーストを介在させない方法での結果にあわせた。
（ｄ）アセトン量の削減効果
その結果、同じ粘度にするために必要なアセトン量は、電極活物質１重量部に対して１．０７重量であった。
従って、ペーストを介在させることで、アセトン量は約２５％削減できることが判明した。
【００２２】
（実施例３：負極スラリーの製造におけるアセトン量の削減効果）
（ａ）材料の秤量
電極活物質にはグラファイト、導電剤には人造黒鉛、結着剤にはポリフッ化ビニリデン（ＰＶＤＦ）、可塑剤にはフタル酸ジブチル（ＤＢＰ）を材料として、２次電池負極用スラリーを調製した。組成は、電極活物質５６重量％、導電剤３重量％、結着剤１６重量％、可塑剤２５重量％とした。分散媒にはアセトンを使用し、電極活物質１重量部に対して０．７８重量部とした。
（ｂ）結着材の分散媒への溶解
溶解はホモディスパーを用いて行った。分散時間は３０分とした。得られた結着材溶液は透明で未溶解部は観察されなかった。
（ｃ）ペーストの調製
可塑剤に活物質、導電材を投入して混練を行った。混練は３軸遊星型ミキサーを用いて３０分行った。結着材溶液は用いず、可塑剤のみでペーストを調製した。
得られたペーストは「べとべと」状態であり、固−液系の充填状態でいえば、固相、液相とも連続で気相が不連続であるファニキュラー域に対応した。
（ｄ）スラリーの調製
得られたペーストに結着材溶液全量を投入してさらに混練を行った。混練は３軸遊星型ミキサーを用いて３０分行った。混練時は水冷による容器内の冷却を行い、容器内圧力は３００ｔｏｒｒで処理した。
【００２３】（ｅ）スラリー評価
得られたスラリーは円筒型粘度計（剪断速度４８／ｓ）で粘度を測定したところ、０．８２Ｐａ．ｓを得た。オスターブレンダーで同程度の粘度を得るには分散媒が電極活物質１重量部に対して１重量を使用しており、約２０％の分散媒の削減となった。このように、本発明の製造方法でアセトン（分散媒）を削減できることが判った。
【００２４】
（実施例４：正極スラリーのペースト状態での保管）
（ａ）材料の秤量とペーストの調製
２次電池正極用スラリーを実施例１の正極スラリーの製造と同じ組成、同じ方法でペーストまで調製した。すなわち、材料の秤量、結着材の分散媒への溶解、ペーストの調製までを実施例１の方法で行った。
（ｂ）スラリーの調製
得られたペーストと結着材溶液を密封状態で３０日間保管した後、ペーストに残りの結着材溶液を投入してさらに混練を行った。混練は３軸遊星型ミキサーを用いて３０分行った。混練時は水冷による容器内の冷却を行い、容器内圧力は３００ｔｏｒｒで処理した。
【００２５】（ｃ）スラリー評価
得られたスラリーは円筒型粘度計（剪断速度４８／ｓ）で粘度を測定し、ｇａｐ５００ｕｍのアプリケーターで成膜した。得られた膜で引っ張り強度試験を行い、破断強度と破断時の伸びを測定した。その結果、強度、伸びは、保管せずにスラリー化した場合と、ほぼ同等の値を示し、保管による悪影響は見られなかった。
【００２６】
【発明の効果】
本発明により、粘度が一定したスラリーを安定して製造でき、かつ、分散媒量を削減できるため、経済効果が高い。
また、一部の分散媒を添加したペースト状態で保管し、必要に応じてスラリー化できるため、材料歩留まりの向上が期待でき、経済効果が高い利点がある。
【図面の簡単な説明】
【図１】本発明の代表的な製造フローシートを示す。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a slurry for a lithium secondary battery electrode, and in particular, first prepares a binder solution by dispersing a binder in a dispersion medium, and comprises a plasticizer, an electrode active material, and a conductive material. If necessary, a part of the binder solution is kneaded, preferably using a three-axis planetary mixer, to obtain a paste, and the prepared binder solution or an unused portion thereof is added. The present invention relates to a method for producing a slurry for a lithium secondary battery electrode, wherein a slurry is obtained by kneading using an axial planetary mixer.
[0002]
[Prior art]
The basic configuration of a lithium secondary battery is a positive electrode, a negative electrode, and a separator holding an electrolyte interposed between both electrodes.
Among these, the positive electrode and the negative electrode are those obtained by applying a slurry obtained by mixing and dispersing a plasticizer in a dispersion medium as necessary to an active material, a conductive material, a binder, and applying the slurry to a current collector such as a metal foil or a metal mesh. Use
As the positive electrode active material, a transition metal lithium oxide is most suitable. For example, lithium manganate (LiMn 2 O 4), lithium cobaltate (LiCoO 2), lithium nickelate (LiNiO 2), etc. are preferable. Further, the negative electrode active material is a known material capable of storing and releasing lithium ions, and for example, a carbon material having lithium ion storing ability is preferable. Among carbon materials, coke-based carbon and graphite-based carbon are more preferable.
The conductive material is a known material having electronic conductivity. For example, natural graphite, carbon black, acetylene black and the like are preferable, and a mixture thereof can also be used.
As the binder, a fluorine-based resin is preferable, and polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), hexafluoropropylene (HFP) and the like are preferable, and a copolymer of these can also be used.
As the dispersion medium, an organic solvent in which the binder can be dissolved is suitable. For example, acetone, methyl ethyl ketone (MEK), tetrahydrofuran (THF), dimethylformamide, dimethylacetamide, tetramethylurea, trimethyl phosphate, N-methyl Pyrrolison (NMP) and the like are preferred.
As the plasticizer to be added as required, an organic solvent that can be replaced with an electrolytic solution after film formation is appropriate, and phthalic acid diesters are preferable.
The current collector is preferably a punched metal or expanded metal of stainless steel, nickel, aluminum, titanium, or copper, and a surface-treated material can also be used. The electrolyte is generally composed of a solvent and a lithium salt dissolved in the solvent. Examples of the solvent include polyethylene carbonate, ethylene carbonate, dimethyl sulfoxide, butyl lactone, sulfolane, 1,2-dimethoxyethane, tetrahydrofuran, diethyl carbonate, methyl ethyl carbonate, organic solvents such as dimethyl carbonate, and one or more of these solvents. Are preferably used in combination. As the lithium salt, LiCF 3 SO 3 , LiAsF 6 , LiClO 4 , LiBF 4 , LiPF 6 and the like are preferable.
[0003]
The slurry required for coating is prepared by kneading the above-mentioned active material, conductive material, binder, dispersion medium and plasticizer at a predetermined ratio. For the preparation, a kneading and dispersing machine such as a homogenizer, a ball mill, a sand mill, a roll mill, and a planetary kneader are used. In addition, a coating method such as gravure coating, blade coating, comma coating, and dip coating is used for coating the current collector.
[0004]
For the preparation of the slurry, there is a method in which each material is charged and kneaded at the same time.However, it is difficult to knead the dispersion medium twice due to a difference in specific gravity of the powder material. (JP-A-9-129222). In this method, in the first kneading, a paste is formed with a small amount of a dispersion medium in order to uniformly knead a powder material having a large specific gravity difference. The second kneading aims at uniform dispersion of the dispersion medium.
[0005]
[Problems to be solved by the invention]
However, it has been difficult to stably obtain a uniform slurry even when the dispersion medium is divided and kneaded as described above. If the slurry to be coated on the current collector is unstable, the coating conditions will not be constant and the characteristics of the coated film will not be stable, affecting the battery characteristics and hindering stable production of the battery. Will be.
In addition, once the slurry is prepared, the entire amount must be quickly used up while maintaining uniformity, so that it is difficult to control the amount of the slurry.
An object of the present invention is to solve the above-mentioned drawbacks and to obtain a stable and uniform electrode slurry. Yet another object of the present invention is to obtain a required amount of slurry when needed.
[0006]
[Means for Solving the Problems]
Therefore, the inventors have paid attention to poor dissolution of the binder in the dispersion medium and poor removal of gas adhering to the powder, as factors that cause inhomogeneity of the slurry. First, as a method for producing a slurry, a binder solution is prepared by dispersing a binder in a dispersion medium, and a plasticizer, an electrode active material, a conductive material, and a part of the binder solution as needed. It has been found that it is useful to obtain a paste corresponding to the funicular region by kneading, and to add a binder solution thereto and knead to obtain a slurry.
[0007]
Thus, the present invention provides a method for producing a slurry for a positive electrode and a negative electrode of a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolytic solution. ,
Step of preparing a binder solution by dispersing the binder in a dispersion medium,
A step of kneading a plasticizer, an electrode active material, a conductive material and, if necessary, a part of the binder solution to obtain a paste corresponding to a funicular region; and It is intended to provide a method for producing a slurry for a lithium secondary battery electrode, which comprises a step of adding a used portion and kneading the slurry to obtain a slurry.
[0008]
More specifically, the present invention relates to a slurry for a positive electrode and a negative electrode of a lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolytic solution. In the manufacturing method of
Step of preparing a binder solution by dispersing the binder in a dispersion medium,
A step of kneading a part of the plasticizer, the electrode active material, the conductive material and, if necessary, the binder solution using a triaxial planetary mixer to obtain a paste corresponding to a funicular region, and preparing the paste into the paste Adding a binder solution or an unused portion thereof, and kneading the mixture with a triaxial planetary mixer to obtain a slurry. provide.
[0009]
In the step of adding the binder solution and kneading to obtain a slurry, it is preferable that the treatment is performed at a pressure lower than the atmospheric pressure and higher than the vapor pressure of the dispersion medium.
The paste obtained by kneading the electrode active material, the conductive material, the plasticizer and a part of the binder solution as required is stored, and the slurry can be obtained by adding and kneading the binder solution as needed. .
[0010]
Here, the "fanicular region" refers to a state in which both the solid phase and the liquid phase are continuous and the gas phase is discontinuous, in the state of solid-liquid filling.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a representative manufacturing flow sheet of the present invention.
The step of preparing a binder solution by dispersing the binder in a dispersion medium is effective as a means for solving poor dissolution of the binder. A dispersing medium effective for dissolving the binder is selected and dissolved using a dispersing kneader. Acetone, MEK, and NMP are examples of the dispersion medium that dissolves the binder, which is a fluororesin, but acetone is preferred because of its ease of handling, cost, toxicity, and the like. Examples of the dispersion kneader include a homogenizer, a ball mill, a sand mill, a roll mill, and a planetary kneader. Care should be taken to disperse the solvent so that no undissolved portion of the binder remains. The dispersion time is from 10 to 120 minutes, preferably from 20 to 40 minutes.
Next, a paste is obtained by kneading the plasticizer, the electrode active material, the conductive material and, if necessary, a part of the binder solution. This is effective for uniform kneading of the powder material because the difference in specific gravity between the electrode active material, which is a powder material, and the conductive material is large. The required amount of liquid is sufficient to wet the entire powder, and in a solid-liquid filling state, it corresponds to a funicular region in which both the solid phase and the liquid phase are continuous and the gas phase is discontinuous. Therefore, the amount of the liquid varies depending on the particle size distribution of the powder, the affinity with the liquid system, and the like. In some cases, only the plasticizer is sufficient without using a binder. Examples of the kneader include a homogenizer, a ball mill, a sand mill, a roll mill, and a planetary kneader. From the viewpoint that a slurry having a constant viscosity can be produced stably, a triaxial planetary kneader is most preferable. The kneading time varies depending on the apparatus, but is generally 10 to 120 minutes, preferably 20 to 40 minutes.
[0013]
The three-axis planetary kneader is composed of three blades that perform planetary motion and a high-speed rotating blade. The two blades rotate and revolve, and the high-speed rotating blades rotate in synchronization with the rotation. This enables kneading without dead space in the container. Also, powders having a large difference in specific gravity or powders having different particle sizes can be easily mixed.
[0014]
Next, the binder solution prepared above or a binder solution not used in the step of obtaining the paste is added to the paste obtained above and kneaded. In this step, it is important to perform the treatment at a pressure lower than the atmospheric pressure and higher than the vapor pressure of the dispersion medium. The gas contained in the powder inhibits the wetting between the dispersion medium and the powder, and should be sufficiently removed to produce a uniform slurry. With this treatment, an ideal slurry region in which the solid phase is discontinuous, the liquid phase is continuous, and the gas phase is zero can be obtained in a solid-liquid system packed state. Vacuum treatment is effective for removing gas, but when the dispersion medium is a low boiling point solvent, boiling evaporation in a vacuum poses a problem. Therefore, the reduction of the solvent is avoided by increasing the vapor pressure of the low boiling point solvent or higher, and the gas adhering to the powder is removed by setting the pressure lower than the atmospheric pressure.
Acetone and MEK are effective as organic solvents capable of dissolving the fluorine resin as the binder, but their vapor pressures are 231 mmHg and 90 mmHg at 25 ° C., and 285 mmHg and 115 mmHg at 30 ° C., respectively. Therefore, it is necessary to adjust the pressure in the container according to the organic solvent used. For example, in the case of kneading using acetone, the pressure in the container is preferably about 300 mmHg, and in the case of MEK, it is preferably about 150 mmHg. By this pressure adjustment, a uniform slurry can be stably manufactured.
Further, since the material temperature during kneading becomes higher than room temperature due to the stirring heat of the kneading device, the container needs to be cooled. Water cooling is optimal for cooling.
[0015] The paste can be stored in a closed container. Therefore, a small amount of coating can be dealt with by taking out the required amount of the stored paste when necessary, adding a binder solution to form a slurry, and dispersing the paste. Economic effects can be expected by omitting the steps.
[0016]
【Example】
Hereinafter, the present invention will be described in detail based on Examples and Comparative Examples.
[0017]
(Example 1 and Comparative Example 1: Difference in kneading method in producing positive electrode slurry)
(A) Measurement of Material Lithium manganate (LiMn 2 O 4 ) for the electrode active material, artificial graphite for the conductive agent, polyvinylidene fluoride (PVDF) for the binder, and dibutyl phthalate (DBP) for the plasticizer Was used as a material to prepare a slurry for a secondary battery positive electrode. The composition was 56% by weight of the electrode active material, 6% by weight of the conductive agent, 15% by weight of the binder, and 23% by weight of the plasticizer. Acetone was used as the dispersion medium, and the amount was 1.64 parts by weight based on 1 part by weight of the electrode active material.
(B) The dissolution of the binder in the dispersion medium was performed using a homodisper. The dispersion time was 30 minutes. The obtained binder solution was transparent and no undissolved portion was observed.
(C) Preparation of paste The active material and the conductive material were added to the plasticizer, and 20 parts by weight of the binder solution were added to the binder solution and kneaded. The kneading was performed for 30 minutes using a triaxial planetary mixer. The obtained paste was in a "sticky" state, which corresponded to a funicular region in which both the solid phase and the liquid phase were continuous and the gas phase was discontinuous in a solid-liquid system filled state.
(D) Preparation of slurry The remaining binder solution was added to the obtained paste and further kneaded. The kneading was performed for 30 minutes using a triaxial planetary mixer. At the time of kneading, the inside of the container was cooled by water cooling, and the mixture was treated at the pressure shown in Table 1.
(E) Evaluation of Slurry The viscosity of the obtained slurry was measured with a cylindrical viscometer (shear rate: 48 / s), and a film was formed with an applicator having a gap of 500 μm. A tensile strength test was performed on the obtained film, and the breaking strength and the elongation at break were measured. The results are shown in Table 1.
As a comparative example, the results in the case of a ball mill in which the materials were simultaneously kneaded without dissolving the binder in the dispersion medium and the results in the case where the binder was dissolved in the dispersion medium and then kneaded by an Oster blender are also described. In both cases, kneading was performed under atmospheric pressure (760 torr).
[0019]
[Table 1]
Table 1 shows the following:
(1) Comparing a ball mill and a blender, a blender in which a binder is dissolved in a dispersion medium has a lower viscosity.
(2) Comparing the example with the comparative example, the example in which the paste in the funicular region is interposed has a lower viscosity.
(3) The example (300 torr) considering the vapor pressure of acetone has the lowest viscosity.
From the above, the dissolution of the binder in the dispersion medium, the preparation of a paste in the funicular region, followed by the formation of a slurry, and the formation of the slurry in consideration of the vapor pressure of the dispersion medium in the formation of the slurry, Was the same amount, the viscosity of the slurry could be reduced. Therefore, it can be seen that the production method according to the present invention can reduce the amount of acetone as compared with the conventional method using a ball mill or a blender.
[0021]
(Example 2 and Comparative Example 2: Effect of reducing the amount of acetone in producing a positive electrode slurry)
(A) Weighing of Materials The effect of reducing the amount of acetone was investigated using a slurry for a secondary battery positive electrode. Lithium cobaltate (LiCoO 2 ) was used as the electrode active material, artificial graphite was used as the conductive agent, polyvinylidene fluoride (PVDF) was used as the binder, and dibutyl phthalate (DBP) was used as the plasticizer. The composition was 70% by weight of the electrode active material, 5% by weight of the conductive agent, 8% by weight of the binder, and 17% by weight of the plasticizer.
(B) Manufacturing Method without Paste Paste Acetone as a dispersion medium was used in an amount of 1.41 parts by weight based on 1 part by weight of the electrode active material. The binder was dissolved in the dispersion medium using a homodisper. The dispersion time was 30 minutes, and the obtained binder solution was transparent and no undissolved portion was observed.
A plasticizer, an active material, and a conductive agent were simultaneously added to the binder solution, and kneaded with a triaxial planetary mixer for 30 minutes. The pressure during kneading was 300 torr. When the viscosity of the obtained slurry was measured with a cylindrical viscometer, it was 1.95 Pa · s.
(C) Production method with paste interposed As in Example 1, a production method with paste interposed was attempted, and the effect of reducing the amount of acetone was determined.
Acetone as a dispersion medium was used in an amount of 0.59 parts by weight based on 1 part by weight of the electrode active material. The binder was dissolved in the dispersion medium using a homodisper. The dispersion time was 30 minutes, and the obtained binder solution was transparent and no undissolved portion was observed.
The active material and the conductive material were added to the plasticizer, and the binder solution was further mixed and kneaded by adding 50 parts by weight of the whole solution. The kneading was performed for 30 minutes using a three-axis planetary mixer to obtain a paste corresponding to the funicular region.
The remaining binder solution was added to the obtained paste and kneaded with a triaxial planetary mixer for 30 minutes. The pressure was 300 torr.
Acetone, which is a dispersion medium, was gradually added to the obtained slurry, and the viscosity of the slurry was adjusted to the result of the above-mentioned method without interposing the paste while kneading was continued.
(D) Effect of reducing the amount of acetone As a result, the amount of acetone required to obtain the same viscosity was 1.07 weight per 1 part by weight of the electrode active material.
Therefore, it was found that the amount of acetone can be reduced by about 25% by interposing the paste.
[0022]
(Example 3: Effect of reducing acetone amount in production of negative electrode slurry)
(A) Weighing of Material A secondary battery negative electrode is made of graphite as an electrode active material, artificial graphite as a conductive agent, polyvinylidene fluoride (PVDF) as a binder, and dibutyl phthalate (DBP) as a plasticizer. A slurry for use was prepared. The composition was 56% by weight of the electrode active material, 3% by weight of the conductive agent, 16% by weight of the binder, and 25% by weight of the plasticizer. Acetone was used as the dispersion medium, and the amount was 0.78 parts by weight based on 1 part by weight of the electrode active material.
(B) The dissolution of the binder in the dispersion medium was performed using a homodisper. The dispersion time was 30 minutes. The obtained binder solution was transparent and no undissolved portion was observed.
(C) Preparation of paste An active material and a conductive material were charged into a plasticizer and kneaded. The kneading was performed for 30 minutes using a triaxial planetary mixer. A paste was prepared only with a plasticizer without using a binder solution.
The obtained paste was in a "sticky" state, which corresponded to a funicular region in which both the solid phase and the liquid phase were continuous and the gas phase was discontinuous in a solid-liquid system filled state.
(D) Preparation of slurry The whole amount of the binder solution was added to the obtained paste and further kneaded. The kneading was performed for 30 minutes using a triaxial planetary mixer. At the time of kneading, the inside of the container was cooled by water cooling, and the inside pressure of the container was treated at 300 torr.
(E) Evaluation of slurry The viscosity of the obtained slurry was measured with a cylindrical viscometer (shear rate: 48 / s). s. In order to obtain the same degree of viscosity with an Oster blender, the dispersion medium is used in an amount of 1 part by weight per 1 part by weight of the electrode active material, and the dispersion medium is reduced by about 20%. Thus, it was found that acetone (dispersion medium) can be reduced by the production method of the present invention.
[0024]
(Example 4: Storage of positive electrode slurry in paste state)
(A) Weighing of Materials and Preparation of Paste A slurry for a secondary battery positive electrode was prepared into a paste by the same composition and the same method as in the production of the positive electrode slurry of Example 1. That is, the method of Example 1 was performed up to the weighing of the material, the dissolution of the binder in the dispersion medium, and the preparation of the paste.
(B) Preparation of slurry After the obtained paste and binder solution were stored in a sealed state for 30 days, the remaining binder solution was added to the paste and further kneaded. The kneading was performed for 30 minutes using a triaxial planetary mixer. At the time of kneading, the inside of the container was cooled by water cooling, and the inside pressure of the container was treated at 300 torr.
(C) Evaluation of Slurry The obtained slurry was measured for viscosity with a cylindrical viscometer (shear rate: 48 / s), and formed into a film with an applicator having a gap of 500 μm. A tensile strength test was performed on the obtained film, and the breaking strength and the elongation at break were measured. As a result, the strength and elongation exhibited almost the same values as those obtained when the slurry was not stored, and no adverse effect was observed by the storage.
[0026]
【The invention's effect】
According to the present invention, a slurry having a constant viscosity can be stably manufactured and the amount of the dispersion medium can be reduced, so that the economic effect is high.
Further, since it can be stored in a paste state to which a part of the dispersion medium is added and can be slurried as required, an improvement in the material yield can be expected, and there is an advantage that the economic effect is high.
[Brief description of the drawings]
FIG. 1 shows a representative manufacturing flow sheet of the present invention.
Claims (5)
結着材を分散媒に分散させて結着材溶液を調製する工程、
可塑剤、電極活物質、導電材及び必要に応じ前記結着材溶液の一部を混練してファニキュラー域に対応するペーストを得る工程、及び
前記ペーストに前記調製した結着材溶液もしくはその未使用部分を添加し、混練してスラリーを得る工程
を包含することを特徴とするリチウム２次電池電極用スラリーの製造方法。Positive electrode, negative electrode, a separator interposed between the positive electrode and the negative electrode, and a method for producing a slurry for the positive electrode and the negative electrode of a lithium secondary battery comprising an electrolytic solution,
Step of preparing a binder solution by dispersing the binder in a dispersion medium,
A step of kneading a plasticizer, an electrode active material, a conductive material and, if necessary, a part of the binder solution to obtain a paste corresponding to a funicular region; and A method for producing a slurry for a lithium secondary battery electrode, comprising a step of adding a used portion and kneading to obtain a slurry.
結着材を分散媒に分散させて結着材溶液を調製する工程、
可塑剤、電極活物質、導電材及び必要に応じ前記結着材溶液の一部を３軸遊星型ミキサーを用いて混練してファニキュラー域に対応するペーストを得る工程、及び
前記ペーストに前記調製した結着材溶液もしくはその未使用部分を添加し、混練してスラリーを得る工程
を包含することを特徴とするリチウム２次電池電極用スラリーの製造方法。Positive electrode, negative electrode, a separator interposed between the positive electrode and the negative electrode, and a method for producing a slurry for the positive electrode and the negative electrode of a lithium secondary battery comprising an electrolytic solution,
Step of preparing a binder solution by dispersing the binder in a dispersion medium,
A step of kneading a part of the plasticizer, the electrode active material, the conductive material and, if necessary, the binder solution using a triaxial planetary mixer to obtain a paste corresponding to a funicular region, and preparing the paste into the paste A method for producing a slurry for a lithium secondary battery electrode, comprising a step of adding a kneaded binder solution or an unused portion thereof and kneading to obtain a slurry.
結着材を分散媒に分散させて結着材溶液を調製する工程、
可塑剤、電極活物質、導電材及び必要に応じ前記結着材溶液の一部を３軸遊星型ミキサーを用いて混練してファニキュラー域に対応するペーストを得る工程、及び
前記ペーストに前記調製した結着材溶液もしくはその未使用部分を添加し、３軸遊星型ミキサーを用いて混練してスラリーを得る工程
を包含することを特徴とするリチウム２次電池電極用スラリーの製造方法。Positive electrode, negative electrode, a separator interposed between the positive electrode and the negative electrode, and a method for producing a slurry for the positive electrode and the negative electrode of a lithium secondary battery comprising an electrolytic solution,
Step of preparing a binder solution by dispersing the binder in a dispersion medium,
A step of kneading a part of the plasticizer, the electrode active material, the conductive material and, if necessary, the binder solution using a triaxial planetary mixer to obtain a paste corresponding to a funicular region, and preparing the paste into the paste A method for producing a slurry for a lithium secondary battery electrode, comprising a step of adding a binder solution or an unused portion thereof and kneading the mixture with a triaxial planetary mixer to obtain a slurry.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29277098A JP3579598B2 (en) | 1998-04-21 | 1998-10-01 | Method for producing slurry for lithium secondary battery electrode |
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| Application Number | Priority Date | Filing Date | Title |
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| JP12536298 | 1998-04-21 | ||
| JP10-125362 | 1998-04-21 | ||
| JP29277098A JP3579598B2 (en) | 1998-04-21 | 1998-10-01 | Method for producing slurry for lithium secondary battery electrode |
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| JP2000012001A JP2000012001A (en) | 2000-01-14 |
| JP3579598B2 true JP3579598B2 (en) | 2004-10-20 |
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| JP29277098A Expired - Fee Related JP3579598B2 (en) | 1998-04-21 | 1998-10-01 | Method for producing slurry for lithium secondary battery electrode |
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Families Citing this family (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4654501B2 (en) * | 2000-10-04 | 2011-03-23 | パナソニック株式会社 | Non-aqueous secondary battery |
| JP2002141060A (en) * | 2000-11-02 | 2002-05-17 | Matsushita Electric Ind Co Ltd | Manufacturing method of negative electrode mixture and non-aqueous system secondary battery using the same |
| KR100542184B1 (en) | 2001-07-19 | 2006-01-10 | 삼성에스디아이 주식회사 | An active material for a battery and a method of preparing the same |
| JP4608862B2 (en) * | 2003-09-05 | 2011-01-12 | 日本ゼオン株式会社 | Method for producing slurry composition for lithium ion secondary battery electrode |
| 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 |
| JP2012221568A (en) * | 2011-04-04 | 2012-11-12 | Toyota Motor Corp | Method for manufacturing positive electrode plate |
| CN103730265A (en) * | 2013-12-31 | 2014-04-16 | 中国船舶重工集团公司第七一八研究所 | Supercapacitor sizing manufacturing method |
| CN103825006B (en) * | 2014-03-17 | 2015-12-30 | 山东润峰集团新能源科技有限公司 | A kind of preparation method of lithium ion battery anode glue size |
| JP6515444B2 (en) * | 2014-05-02 | 2019-05-22 | 日産自動車株式会社 | Method of manufacturing negative electrode active material slurry for non-aqueous electrolyte secondary battery |
| CN104393230B (en) * | 2014-10-29 | 2017-08-11 | 山东圣阳电源股份有限公司 | A kind of compound method of pulp of lithium ion battery |
| CN104466111B (en) * | 2014-12-09 | 2018-01-19 | 河北银隆新能源有限公司 | The preparation technology of lithium battery slurry |
| KR102015431B1 (en) | 2016-03-29 | 2019-08-28 | 주식회사 엘지화학 | Method of preparing electrode slurry for a lithium secondary battery |
| CN105895862A (en) * | 2016-05-18 | 2016-08-24 | 河南田园新能源科技有限公司 | Preparation method of aqueous sizing agent used in cathode of lithium ion battery |
| KR102077789B1 (en) | 2016-11-17 | 2020-02-14 | 주식회사 엘지화학 | Manufacturing method of positive electrode active material slurry |
| CN106654211A (en) * | 2016-12-22 | 2017-05-10 | 深圳拓邦股份有限公司 | Slurry for lithium-ion battery and preparation method of slurry |
| KR102378667B1 (en) * | 2017-11-01 | 2022-03-25 | 주식회사 엘지에너지솔루션 | Evaluation method for cohesion of slurry |
| CN114146590A (en) * | 2021-11-15 | 2022-03-08 | 广东派勒智能纳米科技股份有限公司 | Lithium battery anode and cathode material pulping process and system |
| CN115138231A (en) * | 2022-08-12 | 2022-10-04 | 郑州比克电池有限公司 | Mixing method for improving consistency of lithium ion battery slurry |
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| JP2000012001A (en) | 2000-01-14 |
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