JP4277367B2 - Method for producing non-aqueous electrolyte secondary battery - Google Patents
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- JP4277367B2 JP4277367B2 JP16292099A JP16292099A JP4277367B2 JP 4277367 B2 JP4277367 B2 JP 4277367B2 JP 16292099 A JP16292099 A JP 16292099A JP 16292099 A JP16292099 A JP 16292099A JP 4277367 B2 JP4277367 B2 JP 4277367B2
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- 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
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- 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
Description
【０００１】
【発明の属する技術分野】
本発明は、非水電解質二次電池の製造方法に関し、さらに詳しくは非水電解質二次電池の正極材に塗布される正極合剤塗料の調整方法に関する。
【０００２】
【従来の技術】
近年、非水電解質二次電池は、電子情報機器や携帯電話の普及に伴い、その携帯用電源として需要が急速に増大している。また、非水電解質二次電池は、余剰電力の備蓄用や電気自動車の駆動電源用等の新しい分野での需要も期待されており、それに伴い高容量化が一層強く要請されている。非水電解質二次電池においては、このような実情に伴い、従来と比較して単位体積、単位重量あたりの放電容量が大きい二次電池の開発が進んでいる。
【０００３】
上述した非水電解質二次電池の製造においては、正極活物質を含有する懸濁液がプラネタリーミキサーにて４時間混合され、スラリー状の正極合剤塗料として調整される。正極合剤塗料は、正極材の正極集電体となるアルミニウム箔の両面に未塗布部分を設けながら塗布する、いわゆる間欠塗布が行われる。正極合剤塗料の塗布パターンは、例えばアルミニウム箔の両面とも塗布部分長１６０ｍｍ、未塗布部分長３０ｍｍの繰り返しで塗布され、両面の塗り始め及び塗り終わりの位置は互いに一致するように制御されている。正極材においては、上述したように間欠塗布された正極合剤塗料を乾燥させて正極活物質層が形成される。正極活物質層は、内部の活物質の高密度化を図るためプレスが必要とされている場合には、一般的なプレスロール装置によりプレスされる。
【０００４】
また、非水電解質二次電池の製造においては、負極活物質を含有する懸濁液がプラネタリーミキサーにて４時間混合され、スラリー状の負極合剤塗料として調整される。負極合剤塗料は、負極材の負極集電体となる銅箔の両面に一定間隔ごとに間欠塗布が行われる。負極合剤塗料の塗布パターンは、例えば銅箔の両面とも塗布部分長１６０ｍｍ、未塗布部分長３０ｍｍの繰り返しで塗布され、両面の塗り始め及び塗り終わりの位置は互いに一致するように制御されている。負極材においては、上述したように間欠塗布された負極合剤塗料を乾燥させて負極活物質層が形成される。負極活物質層は、内部の活物質の高密度化を図るためプレスが必要とされている場合には、一般的なプレスロール装置によって加圧処理が施される。
【０００５】
非水電解質二次電池の製造においては、プラネタリーミキサーを用いて正極合剤塗料と負極合剤塗料を調整する工程が、活物質にバインダを吸着させるとともに、正極合剤塗料及び負極合剤塗料における活物質の分散性を向上させるため、重要な工程となっている。
【０００６】
その後、非水電解質二次電池は、正極材及び負極材のそれぞれの合剤塗料未塗布部分にリード線を溶着し、さらに互いの活物質層が対向するように貼り合わせた後、プレス装置等により圧着して発電要素たる電池素子を構成し、この電池素子を外装ケース内に収納して製造される。
【０００７】
上述したように正極合剤塗料及び負極合剤塗料が調整される非水電解質二次電池は、高容量化を達成させる手段として正極合剤塗料中の正極活物質の小径化や、負極合剤塗料に導電剤として易黒鉛化性炭素材料を添加することが提案されている。
【０００８】
【発明が解決しようとする課題】
しかしながら、正極活物質の小径化は、高出力が得られ易くなるため、高電圧効果による負荷特性が向上し、それに伴い電池の安全性が低下する。また、易黒鉛化性炭素材料の添加は、負極合剤塗料を負極集電体に塗工して乾燥装置で乾燥させる際に乾燥不良が発生して塗工速度が減速し、電極材の生産性が低下する。このように、非水電解質二次電池においては、正極合剤塗料や負極合剤塗料の組成を変更させることによって高容量化を達成しようとすると、上述したような種々の問題が発生する。
【０００９】
また、従来の非水電解質二次電池においては、電極材のスリット及びワインディング工程において、活物質層を乾燥させた電極材を所定の長さや大きさに切断したり、切断後の電極材を収納ケース内に組み込むために折り曲げる際に、活物質とバインダとの吸着が弱いために電極材の切り口や折曲げ箇所から活物質が脱落することがある。非水電解質二次電池は、活物質が脱落して混在したままの電池素子を外装ケース内に組み込むと、正極材と負極材との間に介在して両者を隔てるセパレータを脱落した活物質が突き破って正極材と負極材とを導通させ、充放電工程において内部ショートが発生するという問題が生じている。
【００１０】
そこで、本発明は、正極合剤塗料及び負極合剤塗料の組成を変更せずに非水電解質二次電池の高容量化を達成するとともに、電極活物質の脱落による電池の内部ショート（Ｏｐｅｎ ｃｉｒｃｕｉｔ Ｖｏｌｔｅｇｅ。以下、ＯＣＶと略して称する。）率を低減させることを目的に提供されたものである。
【００１１】
【課題を解決するための手段】
上述した目的を達成する本発明に係る非水電解質二次電池の製造方法は、正極材に塗布され正極活物質層を形成する正極合剤塗料のうち溶剤を除いた組成材料を混合する混合工程と、混合工程において混合された混合物を混練する混練工程と、混練工程後に溶剤を加えてさらに混合しかつ正極活物質を分散させる混合分散工程と経て上記正極合剤塗料を調整し、混合工程と上記混合分散工程とは、プラネタリーミキサーを用いて行い、混練工程は、二軸押し出し型の混練装置を用いて行い、組成材料は、少なくとも正極活物質粉末と、結合剤と、導電剤とを含有し、正極活物質層は、摩耗減量が７５ｍｇ／１００回転以下である。
【００１２】
上述した本発明に係る非水電解質二次電池の製造方法によれば、溶剤を除いた組成材料をプラネタリーミキサーを用いて混合し、溶剤を加えて混合分散する前に、混合物の正極合剤組成材料の混練を二軸押し出し型の混練装置を用いて行い、混練後に溶剤を加えてさらに混合しかつ正極活物質をプラネタリーミキサーを用いて分散させることにより、正極合剤塗料中の活物質の分散性が向上して正極合剤塗料の組成を変更せずに二次電池の高容量化が達成される。また、本発明に係る非水電解質二次電池の製造方法によれば、溶剤を加えて混合分散する前に正極合剤組成材料の混練を行うことにより、活物質とバインダとの吸着が強力になり、活物質の脱落による二次電池のＯＣＶ率を低減させる。
【００１３】
【発明の実施の形態】
以下、本発明に係る非水電解質二次電池の製造方法の具体的な実施の形態について詳細に説明する。非水電解質二次電池においては、詳しい図示は省略するが正極材と負極材とからなる電池素子が非水系電解液と共に外装ケース内に封入されて構成される。
【００１４】
正極材は、スラリー状の正極合剤塗料が調整され、正極集電体となるアルミニウム箔に塗布されて正極活物質層が形成されて作製される。正極合剤塗料は、一般式ＬｉxＭＯ2（式中Ｍは一種類以上の遷移金属であり、ｘは０．０５≦ｘ≦１．１０を満足させる数である。）で表される化合物を正極活物質として使用し、この活物質をフッ素系バインダ、例えばポリフルオロビニリデン樹脂等とともに均一に混合し、さらに溶剤たるＮ−メチルピロリドン（以下、ＮＭＰと略して称する。）に均一に分散させて、スラリー状に調整して作製される。
【００１５】
正極活物質は、上記一般式中の遷移金属ＭにＣｏ、Ｎｉ及びＭｎのうち少なくとも一種類を使用することが好ましく、特にＣｏを使用することがより好ましい。このようなリチウム複合酸化物は、リチウム及び遷移金属Ｍのそれぞれの塩、例えば炭酸塩、硝酸塩、硫酸塩、酸化物、水酸化物、ハロゲン化物等を原料として製造され、所望の組成に応じてリチウム塩原料及び遷移金属Ｍの原料をそれぞれ計量し、十分に混合した後に酸素存在雰囲気下６００℃乃至１０００℃の温度範囲で加熱燃焼することにより製造される。このような正極活物質においては、各成分の混合方法を特に限定するものではなく、粉末状の塩類をそのまま乾式の状態で混合しても良く、あるいは粉末状の塩類を水に溶解して水溶液の状態で混合してもよい。
【００１６】
正極合剤塗料には、上述した正極活物質、フッ素系バインダ及び溶剤の他に導電性を向上させるために、リチウムイオンをドープかつ脱ドープし得る炭素材料を導電剤として添加する。炭素材料としては、２０００℃以下の比較的低い温度で焼成して得られる低結晶性炭素材料や、結晶化しやすい原料を３０００℃近くの高温で処理した高結晶性炭素材料等を使用する。炭素材料は、例えば熱分解炭素類、コークス類（ピッチコークス、ニードルコークス、石油コークス等）、人造黒鉛類、天然黒鉛類、ガラス状炭素類、有機高分子化合物焼成体（フラン樹脂等を適当な温度で焼成し炭素化したもの）、炭素繊維、活性炭等を使用する。特に、炭素材料には、面の面間隔が３．７０オングストローム以上、真密度が１．７０ｇ／ｃｃ未満、かつ空気気流中における示差熱分析で７００℃以上に発熱ピークを持たない低結晶性炭素材料や、負極合剤を充填する際の高い真比重が２．１０ｇ／ｃｃ以上の高結晶性炭素材料を使用することが好ましい。
【００１７】
負極材は、スラリー状の負極合剤塗料が調整され、負極集電体となる銅箔に塗布されて負極活物質層が形成されて作製される。負極合剤塗料は、負極活物質をフッ素系バインダ、例えばポリフルオロビニリデン樹脂等とともに均一に混合し、さらに溶剤たるＮＭＰに均一に分散させてスラリー状に調整して作製される。
【００１８】
負極合剤塗料は、リチウムイオンをドープかつ脱ドープし得る炭素材料を活物質として使用する。負極合剤塗料は、負極活物質たる炭素材料をフッ素系バインダ（例えば、ポリフルオロビニリデン樹脂）とともに均一に混合し、その混合物をＮ−メチルピロリドンに均一に分散させて、スラリー状に調整して作製される。炭素材料としては、正極合剤塗料において導電剤として使用したものと同様の炭素材料、すなわち２０００℃以下の比較的低い温度で焼成して得られる低結晶性炭素材料や、結晶化しやすい原料を３０００℃近くの高温で処理した高結晶性炭素材料等を使用する。炭素材料としては、例えば熱分解炭素類、コークス類（ピッチコークス、ニードルコークス、石油コークス等）、人造黒鉛類、天然黒鉛類、ガラス状炭素類、有機高分子化合物焼成体（フラン樹脂等を適当な温度で焼成し炭素化したもの）、炭素繊維、活性炭等を使用する。特に、炭素材料としては、面の面間隔が３．７０オングストローム以上、真密度が１．７０ｇ／ｃｃ未満、かつ空気気流中における示差熱分析で７００℃以上に発熱ピークを持たない低結晶性炭素材料や、負極合剤塗料充填の高い真比重が２．１０ｇ／ｃｃ以上の高結晶性炭素材料を使用することが好ましい。
【００１９】
本実施の形態における非水電解質二次電池においては、非水系電解液の非水溶媒として従来より種々の非水系二次電池において使用される非水系溶媒を使用する。非水系溶媒としては、例えば非水電解質二次電池の場合には、高誘電率溶媒である炭酸プロピレン、炭酸エチレン、炭酸ブチレン、γ−ブチロラクトン等や低粘度溶媒である１．２−ジメトキシエタン、２−メチルテトラヒドロフラン、炭酸ジメチル、炭酸メチルエチル、炭酸ジエテル等を使用することができる。
【００２０】
上述した非水系溶媒に溶解させて、非水系電解液を調整する際に使用する電解質としては、伝導イオン種がリチウムイオンである場合には、ＬｉＣＬＯ4、ＬｉＡｓＦ6、ＬｉＰＦ4、ＬｉＢＦ4、ＬｉＣｌ、ＬｉＢｒ、ＣＨ3ＳＯ3Ｌｉ、ＣＦ3ＳＯ3Ｌｉ等を好ましく使用する。これらは、単独でも２種以上を混合しても用いることができる。なお、使用する電解質は、非水系二次電池における伝導イオン種により異なることは勿論である。
【００２１】
また、本実施の形態に係る非水電解質二次電池においては、この他セパレータ、電池缶、ＰＴＣ素子等については特に限定されるものではなく、従来の非水電解質二次電池と同様のものを使用する。さらに、非水電解質二次電池は、その形状についても特に限定するものではなく、その用途等必要に応じて円筒型形状、角型形状、コイン型形状、ボタン型形状等の種々の形状とする。
【００２２】
上述した構成を有する非水電解質二次電池は、上述した組成の正極合剤塗料が以下のようにして調整される。
【００２３】
正極合剤塗料の調整は、先ず混合機、例えばプラネタリーミキサーを用いて混合工程が行われる。混合工程においては、上述した正極合剤塗料の組成材料のうち溶剤を除いた組成材料、すなわち正極活物質、バインダ及び導電剤がプラネタリーミキサー内に投入され混合される。なお、組成材料中、正極活物質と導電剤とは粉末化して投入し、またバインダは溶剤、例えばＮＭＰに溶解された状態で投入する。
【００２４】
プラネタリーミキサーにおいて混合された混合物は、次いで混練機、例えば二軸押し出し型混練装置を用いて混練工程が行われる。二軸押し出し型混練装置は、材料の性状が液状、粘性物質又は粉末状である複数種類の材料を主として均質に混合、混練処理する連続混練機である。混練工程は、上述したプラネタリーミキサーにおいて混合された混合物を二軸押し出し型混練装置におけるパス回数を１パス又は２パスとして混練を行う。
【００２５】
二軸押し出し型混練装置は、図１及び図２に示すように、二つの同径の円が交差する断面形状を有する筒状の胴体１内に一対のパドル２ａ、２ｂ（以下、特に個別に説明する場合を除いてパドル２と総称する。）が複数組配設されて構成されている。パドル２は、パドル２ａとパドル２ｂとが共に、回転軸Ｃに対する垂直方向の断面形状がなだらかな曲線によって交互にかつ等しい角度を隔てる３組の長径部３と短径部４とを有する形状とされる。
【００２６】
二軸押し出し型混練装置においては、パドル２の長径部３の頂部３ａが胴体１の内周壁に接するとともに、一方のパドル２ａの長径部３の頂部３ａが他方のパドル２ｂの短径部４の頂部４ａに接するように配設される。二軸押し出し型混練装置は、上述したように配設されたパドル２と胴体１の内周壁との間に構成された空間が後述するように装置内に投入された混合物を混練する材料空間Ｄとされる。
【００２７】
二軸押し出し型混練装置は、パドル２ａとパドル２ｂとが異なる方向に、具体的にはパドル２ａが図１及び図２中矢印Ａ方向に、パドル２ｂが同図中矢印Ｂ方向に回転速度比を同一として共動回転する。二軸押し出し型混練装置においては、パドル２ａとパドル２ｂとを異なる方向にかつ同一速度で回転させると、外周上の一点、例えばパドル２ａの長径部３の頂部３ａがパドル２ｂの短径部４の頂部４ｂと、或いはパドル２ａの短径部４の頂部４ａがパドル２ｂの長径部３の頂部３ａとが相接しながら回転する。
【００２８】
混合物は、二軸押し出し型混練機の材料投入口から投入され、回転するパドル２により上述した材料空間Ｄにおいて混練されながら排出口へと搬送される。二軸押し出し型混練装置においては、回転途中で胴体１の内周壁とパドル２との接し方により、図２（ａ）に示す２つの材料空間Ｄ1及び材料空間Ｄ2が構成される。材料空間Ｄ1及びＤ2は、同図（ｂ）及び（ｃ）に示すように、パドル２ａ及びパドル２ｂの回転とともに、順次向かい合いながら重なり合い１つの材料空間Ｄ3に変化する。材料空間Ｄは、パドル２ａの長径部３の頂部３ａ部分と胴体１の内壁とで材料空間Ｄ3が構成された時が最も小さくなり、その後同図（ａ）に示すように、パドル２ａ及びパドル２ｂの回転とともに、再度２つの材料空間Ｄ1及び材料空間Ｄ2に変化する。
【００２９】
このように、二軸押し出し型混練装置に投入された混合物は、上述したようにパドル２の回転に伴う材料空間Ｄの変化により、材料空間Ｄ内で逐次圧縮、膨張が繰り返されて混練される。混合物は、二軸押し出し型混練装置で混練することにより、変化する材料空間Ｄ内において向かい合いながら集合して確実に混ざり合うとともに、正面衝突する機会が増えて均一に混ざり合う。
【００３０】
二軸押し出し型混練装置において混練された混合物は、排出口より活物質やバインダ等の混練物として排出され、溶剤たるＮ−メチルピロリドンとともにさらにプラネタリーミキサーに投入され、再度の混合及び分散工程（以下、単に混合分散工程と称する。）が行われる。
【００３１】
プラネタリーミキサーにおける混合分散工程では、混練物に対して希釈溶媒を任意の量供給することができ、詳しい図示は省略するがニーディングプレートとなる２本のブレードを遊星運動させることで、タンク壁面とのギャップ間を通過する混練物に強い剪断力（剪断速度、剪断応力）を与え、回転運動しているディスパーによりさらに塗料の分散性が向上する。また、プラネタリーミキサーにおける混合分散工程では、混合時に真空ポンプ装置等によりタンク内を真空状態にすることで混練物の脱法作業ができ、混練物のさらなる混合と溶解を行う。
【００３２】
上述した正極合剤塗料の調整においては、混練工程を経て混合分散工程が行われるプラネタリーミキサーに投入する際の混練物におけるバインダと活物質との吸着を向上させる仕込み固形分が８０％乃至９５％となるような量に調整された溶剤を投入して混練が行われる。正極合剤塗料は、アルミニウム箔の全体にわたって均一に塗布して分散性を向上させることと、活物質に安全性を向上させるアルミニウム添加活物質を使用すると発熱する温度が高い温度にシフトすることを利用して混練工程後の混練物の仕込み固形分を８０％乃至９５％の範囲内に規制する。正極合剤塗料は、投入する溶剤量を調整して仕込み固形分の数値を一定範囲内に限定することで、二次凝集活物質が効率よく一次粒子に混練され、さらに次工程たるプラネタリーミキサーでの混合分散で一次粒子までの分散性とその安定性向上の実現が可能となり、凝集しやすく分散性の悪い活物質の分散安定性が改善される。
【００３３】
また、正極合剤塗料は、上述した仕込み固形分が８０％乃至９５％の混練物がプラネタリーミキサーに溶剤とともに投入され、全塗料重量に対する全固形分比（分散固形分。以下、Ｎ．Ｖと略して称する。）を７０％乃至９５％の範囲に調整してアルミニウム箔に塗布される。正極合剤塗料は、Ｎ．Ｖを上述した範囲に規制することで、正極材に形成される正極活物質層の体積密度が向上する。正極合剤塗料は、Ｎ．Ｖを７０％より低くするように調整すると混合分散工程において正極合剤塗料の組成材料に十分な剪断力が負荷できず、Ｎ．Ｖを９５％より高くするように調整すると全塗料重量中の溶剤量が少ないため、活物質を含む無機粉体を湿潤させることができず、二次凝集活物質を効率よく一次粒子とする十分な混練を行うことができない。また、正極合剤塗料は、Ｎ．Ｖを７０％より低くするように調整すると、混練された塗料に対して希釈溶剤が多いため、プラネタリーミキサーでの分散効率が低下する。
【００３４】
正極材は、上述したように調整された正極合剤塗料を正極集電体となるアルミニウム箔の両面に間欠塗布し、乾燥させることにより正極活物質層が形成される。なお、正極材においては、正極合剤塗料の塗布方法や塗布のための装置等を限定するものではない。
【００３５】
また、負極合剤塗料の調整方法は、本実施の形態においては特に限定するものではなく、上述した正極合剤塗料と同様の方法により調整しても良く、またプラネタリーミキサーのみによって混合分散を行うものであってもよい。負極材は、調整された負極合剤塗料を負極集電体となる銅箔の両面に間欠塗布し、乾燥させることにより負極活物質層が形成される。なお、本実施の形態においては、また、正極材と同様に負極合剤塗料の塗布方法や塗布のための装置等を限定するものではない。
【００３６】
非水電解質二次電池においては、上述したように作製された正極材と負極材とが所望の大きさに切断される。非水電解質二次電池は、切断された正極材と負極材とを相互に活物質層が対向するようにセパレータを介して積層しかつ巻回して電池素子を構成し、この電池素子を収納ケース内に封入して製造される。
【００３７】
【実施例】
本発明に係る非水電解質二次電池の製造方法について、以下に具体的な比較例及び実施例をあげて説明する。先ず、以下に示す組成及び調整方法で調整した正極合剤塗料及び負極合剤塗料を用いた比較例及び実施例に係る二次電池を作製した。
【００３８】
比較例１
正極合剤塗料組成
正極活物質：ＬｉＣｏＯ2 １００重量部
導電剤 ：グラファイト ２６重量部
バインダ ：ポリフルオロビニリデン樹脂（Ｎ．Ｖ＝５％） ３０重量部
溶剤 ：ＮＭＰ（Ｎ−メチルピロリドン） ５２重量部
負極合剤塗料組成
負極活物質：グラファイト １００重量部
添加剤 ：しゅう酸 ４重量部
バインダ ：ポリフルオロビニリデン樹脂（Ｎ．Ｖ＝５％） ８０重量部
溶剤 ：ＮＭＰ（Ｎ−メチルピロリドン） ２０重量部
上述した組成の材料を混合機のみを用いて混合分散を行って得た正極合剤塗料を厚さ２０μｍのアルミニウム箔に全厚１８０μｍになるように、負極合剤塗料を銅箔に塗布して正極材及び負極材として電池素子を構成し、電解液と共に電池缶内に封入して二次電池を作製した。
【００３９】
実施例１
プラネタリーミキサーで上述した組成材料を溶剤を除いて混合した後、その混合物を仕込み固形分が８０％（ＮＭＰ３９重量部含む。）となるように二軸押し出し型混練装置で１パス処理した。その後、二軸押し出し型混練装置から排出された混練物をさらにプラネタリーミキサーにて分散固形分７５．０％（ＮＭＰ１３重量部含む。）となるように混合分散し、調整された正極合剤塗料を比較例１と同様に厚さ２０μｍのアルミニウム箔に全厚１８０μｍになるように塗工して正極材を得た。この正極材と負極材とで電池素子を構成し、電解液と共に電池缶内に封入して電池を作製した。
【００４０】
実施例２
プラネタリーミキサーで上述した組成材料を溶剤を除いて混合した後、その混合物を仕込み固形分が８３％（ＮＭＰ３２重量部含む。）となるように二軸押し出し型混練装置で１パス処理した。その後、二軸押し出し型混練装置から排出された混練物をさらにプラネタリーミキサーにて分散固形分７２．５％（ＮＭＰ２７重量部含む。）となるように混合分散し、調整された正極合剤塗料を比較例１と同様に厚さ２０μｍのアルミニウム箔に全厚１８０μｍになるように塗工して正極材を得た。この正極材と負極材とで電池素子を構成し、電解液と共に電池缶内に封入して電池を作製した。
【００４１】
実施例３
プラネタリーミキサーで上述した組成材料を溶剤を除いて混合した後、その混合物を仕込み固形分が９０％（ＮＭＰ１７重量部含む。）となるように二軸押し出し型混練装置で１パス処理した。その後、二軸押し出し型混練装置から排出された混練物をさらにプラネタリーミキサーにて分散固形分７５．０％（ＮＭＰ３５重量部含む。）となるように混合分散し、調整された正極合剤塗料を比較例１と同様に厚さ２０μｍのアルミニウム箔に全厚１８０μｍになるように塗工して正極材を得た。この正極材と負極材とで電池素子を構成し、電解液と共に電池缶内に封入して電池を作製した。
【００４２】
実施例４
プラネタリーミキサーで上述した組成材料を溶剤を除いて混合した後、その混合物を仕込み固形分が９５％（ＮＭＰ８重量部含む。）となるように二軸押し出し型混練装置で１パス処理した。その後、二軸押し出し型混練装置から排出された混練物をさらにプラネタリーミキサーにて分散固形分７５．０％（ＮＭＰ４４重量部含む。）となるように混合分散し、調整された正極合剤塗料を比較例１と同様に厚さ２０μｍのアルミニウム箔に全厚１８０μｍになるように塗工して正極材を得た。この正極材と負極材とで電池素子を構成し、電解液と共に電池缶内に封入して電池を作製した。
【００４３】
実施例５
プラネタリーミキサーで上述した組成材料を溶剤を除いて混合した後、その混合物を仕込み固形分が８３％（ＮＭＰ３２重量部含む。）となるように二軸押し出し型混練装置で２パス処理した。その後、二軸押し出し型混練装置から排出された混練物をさらにプラネタリーミキサーにて分散固形分７５．０％（ＮＭＰ２０重量部含む。）となるように混合分散した正極合剤塗料を比較例１と同様に厚さ２０μｍのアルミニウム箔に全厚１８０μｍになるように塗工して正極材を得た。この正極材と負極材とで電池素子を構成し、電解液と共に電池缶内に封入して電池を作製した。
【００４４】
実施例６
プラネタリーミキサーで上述した組成材料を溶剤を除いて組成材料を混合した後、その混合物を仕込み固形分が８３％（ＮＭＰ３２重量部含む。）となるように二軸押し出し型混練装置で２パス処理した。その後、二軸押し出し型混練装置から排出された混練物をさらにプラネタリーミキサーにて分散固形分７２．５％（ＮＭＰ２７重量部含む。）となるように混合分散し、調整された正極合剤塗料を比較例１と同様に厚さ２０μｍのアルミニウム箔に全厚１８０μｍになるように塗工して正極材を得た。この正極材と負極材とで電池素子を構成し、電解液と共に電池缶内に封入して電池を作製した。
【００４５】
上述したように比較例及び各実施例において作製した各二次電池について、面積密度と体積密度を算出した。各二次電池の面積密度と体積密度とは、正極材を特定の大きさにそれぞれ打ち抜き、打ち抜いた正極材の重量と全厚を測定して算出した。なお、体積密度の値は、活物質の分散の程度により同じ塗工量でもその重量と全厚が異なってくる、具体的には分散性が向上すると活物質が密に詰め込まれるため重くかつ厚くなることから、分散性の程度を示す指標として用いることができる。
【００４６】
また、比較例及び各実施例の二次電池に用いた正極材について、正極活物質層の塗膜の摩耗減量を調査した。塗膜の摩耗減量は、図３に示す試験機のターンテーブル２０に取り付けた電極試験片２１の上に回転可能に配設された摩耗輪２２を下ろし、ターンテーブル２０を同図中矢印Ｅ方向に回転させ、ターンテーブル２０の回転総数が１００回に達した時点で試験機を停止させ、電極試験片２１から離脱した摩耗粉の質量を測り、下記の式によって算出した。
【００４７】
摩耗減量(mg)＝試験前電極試験片質量(mg)−試験前電極試験片質量(mg)
摩耗減量(mm3)＝摩耗減量(mg)／摩耗粉密度(g/cm3)
【００４８】
なお、ターンテーブル２０の回転が１００回に満たない場合には下記の式を用いて摩耗減量を算出する。
【００４９】
摩耗減量(mg)＝（試験前電極試験片質量(mg)−試験前電極試験片質量(mg)）×（１００／試験回転数）
摩耗減量(mm3)＝摩耗減量(mg)／摩耗粉密度(g/cm3)
【００５０】
さらに、ＯＣＶ率の評価は、比較例及び各実施例の電池を用いて、一般環境（２５℃・６０ＲＨ％）で１２時間のエージングを経て、５００ｍＡの定電流条件で４．２５Ｖまで充電し、ついで充電４時間後、さらに３０日後の電圧を測定して電圧の降下分を自然放電率とし、この値が１０％を越えたものを不良と評価してその割合を算出した。
【００５１】
上述した各調査の結果を表１、図４及び図５に示す。
【００５２】
【表１】
表１及び図４に示すように、混合機で混合した後、混練機で混練処理した各実施例に係る二次電池は、混合機のみで正極合剤塗料を調整した比較例１に係る二次電池に比して、摩耗減量が低下し、ＯＣＶ率が低減していることが確認できる。また、表１及び図５に示すように、各実施例に係る二次電池は、活物質の体積密度の値が上昇していることが確認でき、このことから各実施例の二次電池は比較例の二次電池に比して分散性が向上していると判断できる。
【００５４】
【発明の効果】
上述した本発明に係る非水電解質二次電池の製造方法によれば、溶剤を除いた組成材料をプラネタリーミキサーを用いて混合し、溶剤を加えて混合分散する前に、混合物の正極合剤組成材料の混練を二軸押し出し型の混練装置を用いて行い、混練後に溶剤を加えてさらに混合しかつ正極活物質をプラネタリーミキサーを用いて分散させる、即ち溶剤を加えて混合分散する前に正極合剤組成材料の混練を行うことにより、正極合剤塗料中の活物質の分散性が向上して二次電池の高容量化を図ることができる。また、本発明に係る非水電解質二次電池の製造方法によれば、溶剤を加えて混合分散する前に正極合剤組成材料の混練を行うことにより、活物質とバインダとの吸着が強力になり、活物質の脱落による二次電池のＯＣＶ率が低減できる。
【図面の簡単な説明】
【図１】二軸押し出し型混練装置のパドルの組み合わせ状態を示す斜視図である。
【図２】パドルによる混練の状態を説明するための図である。
【図３】電極試験片が乗せられた試験機のターンテーブルの斜視図である
【図４】摩耗減量とＯＣＶ率との関係を示す特性図である。
【図５】体積密度とＯＣＶ率との関係を示す特性図である。
【符号の説明】
１ 胴体，２ パドル，３ 長径部，４ 短径部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a nonaqueous electrolyte secondary battery, and more particularly to a method for adjusting a positive electrode mixture paint applied to a positive electrode material of a nonaqueous electrolyte secondary battery.
[0002]
[Prior art]
In recent years, the demand for nonaqueous electrolyte secondary batteries has been rapidly increasing as portable power sources with the spread of electronic information devices and mobile phones. In addition, non-aqueous electrolyte secondary batteries are also expected to be used in new fields such as storage of surplus power and drive power for electric vehicles, and accordingly, higher capacity is strongly demanded. In the non-aqueous electrolyte secondary battery, development of a secondary battery having a larger discharge capacity per unit volume and unit weight than the conventional one is progressing with such a situation.
[0003]
In the manufacture of the non-aqueous electrolyte secondary battery described above, a suspension containing a positive electrode active material is mixed for 4 hours by a planetary mixer, and adjusted as a slurry-like positive electrode mixture paint. The positive electrode mixture paint is applied by applying so-called intermittent application while providing uncoated portions on both surfaces of an aluminum foil serving as a positive electrode current collector of the positive electrode material. The coating pattern of the positive electrode mixture paint is, for example, applied on both sides of the aluminum foil by repeating the application part length of 160 mm and the non-application part length of 30 mm, and the positions of the start and end of application on both sides are controlled to coincide with each other. . In the positive electrode material, the positive electrode mixture paint applied intermittently as described above is dried to form a positive electrode active material layer. The positive electrode active material layer is pressed by a general press roll device when a press is required to increase the density of the active material inside.
[0004]
In the production of a non-aqueous electrolyte secondary battery, a suspension containing a negative electrode active material is mixed for 4 hours by a planetary mixer to prepare a slurry-like negative electrode mixture paint. The negative electrode mixture coating material is intermittently applied to both surfaces of a copper foil serving as a negative electrode current collector of the negative electrode material at regular intervals. The application pattern of the negative electrode mixture paint is, for example, applied on both sides of the copper foil repeatedly by applying an applied part length of 160 mm and an unapplied part length of 30 mm, and the positions of the start and end of application on both sides are controlled to coincide with each other. . In the negative electrode material, the negative electrode mixture paint applied intermittently as described above is dried to form the negative electrode active material layer. The negative electrode active material layer is subjected to pressure treatment by a general press roll device when a press is required to increase the density of the active material inside.
[0005]
In the production of a non-aqueous electrolyte secondary battery, the step of adjusting the positive electrode mixture paint and the negative electrode mixture paint using a planetary mixer adsorbs the binder to the active material, and the positive electrode mixture paint and the negative electrode mixture paint This is an important process for improving the dispersibility of the active material.
[0006]
Thereafter, the non-aqueous electrolyte secondary battery is prepared by welding the lead wires to the uncoated portions of the positive electrode material and the negative electrode material, and further bonding them so that the active material layers face each other. A battery element which is a power generation element is configured by pressure bonding with the above, and the battery element is housed in an outer case and manufactured.
[0007]
As described above, the non-aqueous electrolyte secondary battery in which the positive electrode mixture paint and the negative electrode mixture paint are adjusted is used as a means for achieving a high capacity, by reducing the diameter of the positive electrode active material in the positive electrode mixture paint or the negative electrode mixture. It has been proposed to add an easily graphitizable carbon material as a conductive agent to the paint.
[0008]
[Problems to be solved by the invention]
However, the reduction in the diameter of the positive electrode active material makes it easy to obtain a high output, so that the load characteristics due to the high voltage effect are improved, and the safety of the battery is lowered accordingly. In addition, the addition of graphitizable carbon material is caused by poor coating when the negative electrode mixture paint is applied to the negative electrode current collector and dried with a drying device, and the coating speed is reduced. Sex is reduced. As described above, in the non-aqueous electrolyte secondary battery, various problems as described above occur when an attempt is made to increase the capacity by changing the composition of the positive electrode mixture paint or the negative electrode mixture paint.
[0009]
Also, in the conventional non-aqueous electrolyte secondary battery, in the slit and winding process of the electrode material, the electrode material dried from the active material layer is cut into a predetermined length or size, or the cut electrode material is stored. When bending for incorporation into the case, the active material may fall off from the cut end or the bent portion of the electrode material due to weak adsorption between the active material and the binder. In non-aqueous electrolyte secondary batteries, when a battery element in which the active material has been dropped and mixed is incorporated in the outer case, the active material that has fallen off the separator that is interposed between the positive electrode material and the negative electrode material is separated. There is a problem that the positive electrode material and the negative electrode material are made conductive by breaking through and an internal short circuit occurs in the charge / discharge process.
[0010]
Accordingly, the present invention achieves a higher capacity of the nonaqueous electrolyte secondary battery without changing the composition of the positive electrode mixture paint and the negative electrode mixture paint, and the internal short circuit (Open circuit) of the battery due to the dropping of the electrode active material. Voltage (hereinafter abbreviated as OCV)) provided for the purpose of reducing the rate.
[0011]
[Means for Solving the Problems]
The nonaqueous electrolyte secondary battery manufacturing method according to the present invention that achieves the above-described object includes a mixing step of mixing a composition material excluding a solvent in a positive electrode mixture paint applied to a positive electrode material to form a positive electrode active material layer And adjusting the positive electrode mixture paint through a kneading step of kneading the mixture mixed in the mixing step, a mixing and dispersing step of adding a solvent after the kneading step and further mixing and dispersing the positive electrode active material,The mixing step and the mixing and dispersing step are performed using a planetary mixer, the kneading step is performed using a biaxial extrusion type kneading apparatus, and the composition material includes at least a positive electrode active material powder, a binder, a conductive material. And the positive electrode active material layer has a weight loss of 75 mg / 100 rotations or less.
[0012]
According to the method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention described above, the composition material excluding the solvent is used.Mix using a planetary mixer,Before adding solvent and mixing and dispersingOf the mixtureKneading the positive electrode mixture composition materialUsing a twin screw extrusion type kneaderDoneAfter kneading, a solvent is added and further mixed, and the positive electrode active material is dispersed using a planetary mixer.This improves the dispersibility of the active material in the positive electrode mixture paint and improves the positive electrode mixture coating.FeeThe capacity of the secondary battery can be increased without changing the composition. Further, according to the method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention, the positive electrode mixture composition material is kneaded before adding and mixing the solvent, thereby strongly adsorbing the active material and the binder. Thus, the OCV rate of the secondary battery due to the dropping of the active material is reduced.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments of a method for producing a nonaqueous electrolyte secondary battery according to the present invention will be described in detail. In the nonaqueous electrolyte secondary battery, although not shown in detail, a battery element composed of a positive electrode material and a negative electrode material is enclosed in an outer case together with a nonaqueous electrolyte solution.
[0014]
The positive electrode material is prepared by preparing a positive electrode active material layer by preparing a slurry-like positive electrode mixture paint and applying it to an aluminum foil serving as a positive electrode current collector. The positive electrode mixture paint has the general formula LixMO2(Wherein M is one or more transition metals and x is a number satisfying 0.05 ≦ x ≦ 1.10) as a positive electrode active material, It is prepared by mixing uniformly with a fluorine-based binder, such as a polyfluorovinylidene resin, and further uniformly dispersing in N-methylpyrrolidone (hereinafter abbreviated as NMP), which is a solvent, to prepare a slurry.
[0015]
As the positive electrode active material, it is preferable to use at least one of Co, Ni, and Mn as the transition metal M in the above general formula, and it is more preferable to use Co in particular. Such lithium composite oxides are manufactured using respective salts of lithium and transition metal M, such as carbonates, nitrates, sulfates, oxides, hydroxides, halides, and the like, depending on the desired composition. The lithium salt raw material and the transition metal M raw material are weighed and mixed sufficiently, and then heated and burned in a temperature range of 600 ° C. to 1000 ° C. in an oxygen-containing atmosphere. In such a positive electrode active material, the mixing method of each component is not particularly limited, and powdery salts may be mixed in a dry state as they are, or an aqueous solution obtained by dissolving powdery salts in water. You may mix in the state of.
[0016]
In addition to the positive electrode active material, the fluorine-based binder, and the solvent, a carbon material that can be doped and dedoped with lithium ions is added to the positive electrode mixture paint as a conductive agent. As the carbon material, a low crystalline carbon material obtained by firing at a relatively low temperature of 2000 ° C. or less, a highly crystalline carbon material obtained by treating a raw material that is easily crystallized at a high temperature of about 3000 ° C., or the like is used. Examples of the carbon material include pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), artificial graphites, natural graphites, glassy carbons, and fired organic polymer compounds (furan resin, etc.). Use carbon fiber, activated carbon, etc.). In particular, the carbon material has a low crystalline carbon with a surface spacing of 3.70 angstroms or more, a true density of less than 1.70 g / cc, and no exothermic peak at 700 ° C. or higher by differential thermal analysis in an air stream. It is preferable to use a highly crystalline carbon material having a high true specific gravity of 2.10 g / cc or more when filling the material and the negative electrode mixture.
[0017]
The negative electrode material is prepared by preparing a negative electrode active material layer by preparing a slurry-like negative electrode mixture paint and applying it to a copper foil serving as a negative electrode current collector. The negative electrode mixture paint is prepared by uniformly mixing a negative electrode active material together with a fluorine-based binder, for example, a polyfluorovinylidene resin, and further uniformly dispersing it in NMP as a solvent to prepare a slurry.
[0018]
The negative electrode mixture paint uses, as an active material, a carbon material that can be doped and dedoped with lithium ions. The negative electrode mixture paint is prepared by uniformly mixing a carbon material, which is a negative electrode active material, together with a fluorine-based binder (for example, polyfluorovinylidene resin), and uniformly dispersing the mixture in N-methylpyrrolidone to prepare a slurry. Produced. As the carbon material, the same carbon material used as the conductive agent in the positive electrode mixture paint, that is, a low crystalline carbon material obtained by firing at a relatively low temperature of 2000 ° C. or less, or a raw material that is easily crystallized is 3000. A highly crystalline carbon material treated at a high temperature close to ℃ is used. Examples of carbon materials include pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), artificial graphite, natural graphite, glassy carbons, and fired organic polymer compounds (furan resin, etc.) Use carbon fiber, activated carbon, etc.). In particular, as a carbon material, a low crystalline carbon having a face spacing of 3.70 angstroms or more, a true density of less than 1.70 g / cc, and having no exothermic peak at 700 ° C. or higher by differential thermal analysis in an air stream. It is preferable to use a material or a highly crystalline carbon material having a high true specific gravity of 2.10 g / cc or more with a negative electrode mixture paint filling.
[0019]
In the nonaqueous electrolyte secondary battery in the present embodiment, nonaqueous solvents conventionally used in various nonaqueous secondary batteries are used as the nonaqueous solvent of the nonaqueous electrolyte solution. As the non-aqueous solvent, for example, in the case of a non-aqueous electrolyte secondary battery, propylene carbonate which is a high dielectric constant solvent, ethylene carbonate, butylene carbonate, γ-butyrolactone and the like, 1.2-dimethoxyethane which is a low viscosity solvent, 2-methyltetrahydrofuran, dimethyl carbonate, methyl ethyl carbonate, diether carbonate and the like can be used.
[0020]
The electrolyte used for preparing the non-aqueous electrolyte by dissolving in the non-aqueous solvent described above is LiCLO when the conductive ion species is lithium ion.Four, LiAsF6, LiPFFour, LiBFFour, LiCl, LiBr, CHThreeSOThreeLi, CFThreeSOThreeLi or the like is preferably used. These can be used alone or in admixture of two or more. Of course, the electrolyte to be used varies depending on the conductive ion species in the non-aqueous secondary battery.
[0021]
Further, in the nonaqueous electrolyte secondary battery according to the present embodiment, the separator, battery can, PTC element and the like are not particularly limited, and the same as the conventional nonaqueous electrolyte secondary battery. use. Further, the shape of the nonaqueous electrolyte secondary battery is not particularly limited, and may be various shapes such as a cylindrical shape, a square shape, a coin shape, a button shape, etc., as necessary for its use and the like. .
[0022]
In the non-aqueous electrolyte secondary battery having the above-described configuration, the positive electrode mixture paint having the above-described composition is adjusted as follows.
[0023]
For the adjustment of the positive electrode mixture paint, a mixing process is first performed using a mixer, for example, a planetary mixer. In the mixing step, the composition material excluding the solvent among the composition materials of the positive electrode mixture paint described above, that is, the positive electrode active material, the binder, and the conductive agent are charged into the planetary mixer and mixed. In the composition material, the positive electrode active material and the conductive agent are pulverized and charged, and the binder is charged in a solvent, for example, NMP.
[0024]
The mixture mixed in the planetary mixer is then subjected to a kneading step using a kneader, for example, a biaxial extrusion kneader. The biaxial extrusion type kneader is a continuous kneader that mainly uniformly mixes and kneads a plurality of types of materials whose properties are liquid, viscous substance, or powder. In the kneading step, the mixture mixed in the above-described planetary mixer is kneaded by setting the number of passes in the biaxial extrusion kneader as one pass or two passes.
[0025]
As shown in FIGS. 1 and 2, the biaxial extrusion type kneader includes a pair of
[0026]
In the biaxial extrusion kneader, the top 3a of the
[0027]
In the biaxial extrusion kneader, the paddle 2a and the
[0028]
The mixture is fed from the material charging port of the biaxial extrusion kneader, and conveyed to the discharge port while being kneaded in the material space D by the
[0029]
As described above, the mixture charged in the twin-screw extrusion kneader is kneaded by being repeatedly compressed and expanded in the material space D due to the change in the material space D accompanying the rotation of the
[0030]
The mixture kneaded in the biaxial extrusion type kneader is discharged as a kneaded material such as an active material and a binder from a discharge port, and is further introduced into a planetary mixer together with N-methylpyrrolidone as a solvent, and mixed and dispersed again ( Hereinafter, this is simply referred to as a mixing and dispersing step.
[0031]
In the mixing and dispersing step in the planetary mixer, an arbitrary amount of a diluting solvent can be supplied to the kneaded product, and although detailed illustration is omitted, two blades serving as a kneading plate are moved in a planetary motion, A strong shearing force (shear rate, shearing stress) is applied to the kneaded material passing between the gaps, and the dispersibility of the rotational movement further improves the dispersibility of the paint. In the mixing and dispersing step in the planetary mixer, the kneaded product can be removed by evacuating the tank with a vacuum pump device or the like during mixing, and the kneaded product is further mixed and dissolved.
[0032]
In the adjustment of the positive electrode mixture paint described above, the charged solid content for improving the adsorption of the binder and the active material in the kneaded product when being put into the planetary mixer in which the mixing and dispersing step is performed through the kneading step is 80% to 95%. The kneading is carried out by introducing a solvent adjusted to an amount of%. The positive electrode mixture paint is applied uniformly over the entire aluminum foil to improve dispersibility, and when an aluminum-added active material that improves safety is used as the active material, the heat generation temperature shifts to a higher temperature. Utilizing it, the charged solid content of the kneaded product after the kneading step is regulated within the range of 80% to 95%. The positive electrode mixture paint is a planetary mixer in which the secondary agglomerated active material is efficiently kneaded into primary particles by adjusting the amount of solvent to be added and limiting the value of the charged solid content within a certain range. It is possible to realize the dispersibility up to the primary particles and the improvement of the stability by mixing and dispersing in the above, and the dispersion stability of the active material which is easy to aggregate and has poor dispersibility is improved.
[0033]
In the positive electrode mixture paint, the above-mentioned kneaded material having a charged solid content of 80% to 95% is charged into a planetary mixer together with a solvent, and the total solid content ratio relative to the total paint weight (dispersed solid content. Is abbreviated as 70% to 95% and applied to the aluminum foil. The positive electrode mixture paint is N.I. By regulating V within the above-described range, the volume density of the positive electrode active material layer formed on the positive electrode material is improved. The positive electrode mixture paint is N.I. When V is adjusted to be lower than 70%, a sufficient shearing force cannot be applied to the composition material of the positive electrode mixture paint in the mixing and dispersing step. If the V is adjusted to be higher than 95%, the amount of solvent in the total coating weight is small, so that the inorganic powder containing the active material cannot be wetted, and the secondary aggregated active material is efficiently converted into primary particles. Kneading cannot be performed. Further, the positive electrode mixture paint is N.I. If the V is adjusted to be lower than 70%, the dispersion efficiency in the planetary mixer is lowered because there are more dilution solvents with respect to the kneaded paint.
[0034]
The positive electrode material is formed by intermittently applying the positive electrode mixture paint prepared as described above to both surfaces of an aluminum foil serving as a positive electrode current collector and drying it. In addition, in the positive electrode material, the application method of the positive electrode mixture paint, the apparatus for application, and the like are not limited.
[0035]
In addition, the method for adjusting the negative electrode mixture paint is not particularly limited in the present embodiment, and may be adjusted by the same method as that for the positive electrode mixture paint described above, and mixing and dispersion may be performed only by a planetary mixer. You may do it. The negative electrode material is formed by intermittently applying the adjusted negative electrode mixture paint on both sides of a copper foil serving as a negative electrode current collector and drying the negative electrode active material layer. In the present embodiment, similarly to the positive electrode material, the application method of the negative electrode mixture paint, the apparatus for application, and the like are not limited.
[0036]
In the nonaqueous electrolyte secondary battery, the positive electrode material and the negative electrode material manufactured as described above are cut into a desired size. A non-aqueous electrolyte secondary battery is configured by stacking and winding a cut positive electrode material and a negative electrode material with a separator so that the active material layers face each other, and forming a battery element. It is manufactured by enclosing it inside.
[0037]
【Example】
The manufacturing method of the nonaqueous electrolyte secondary battery according to the present invention will be described below with reference to specific comparative examples and examples. First, the secondary battery which concerns on the comparative example and Example using the positive mix paint and negative mix paint which were adjusted with the composition and adjustment method which are shown below was produced.
[0038]
Comparative Example 1
Positive mix paint composition
Cathode active material: LiCoO2 100 parts by weight
Conductive agent: Graphite 26 parts by weight
Binder: Polyfluorovinylidene resin (NV = 5%) 30 parts by weight
Solvent: 52 parts by weight of NMP (N-methylpyrrolidone)
Negative electrode mixture paint composition
Negative electrode active material: 100 parts by weight of graphite
Additive:
Binder: Polyfluorovinylidene resin (NV = 5%) 80 parts by weight
Solvent: 20 parts by weight of NMP (N-methylpyrrolidone)
The negative electrode mixture paint was applied to the copper foil so that the total thickness of the positive electrode mixture paint obtained by mixing and dispersing the materials having the above-described composition on a 20 μm thick aluminum foil was 180 μm. A battery element was constituted as a positive electrode material and a negative electrode material, and sealed in a battery can together with an electrolyte solution to produce a secondary battery.
[0039]
Example 1
After mixing the above-described composition materials with a planetary mixer with the solvent removed, the mixture was charged and subjected to one pass treatment with a twin-screw extrusion kneader so that the solid content was 80% (including 39 parts by weight of NMP). Thereafter, the kneaded material discharged from the biaxial extrusion kneader is further mixed and dispersed by a planetary mixer so that the dispersed solid content is 75.0% (including 13 parts by weight of NMP), and the adjusted positive electrode mixture paint Was applied to an aluminum foil having a thickness of 20 μm in the same manner as in Comparative Example 1 so as to have a total thickness of 180 μm to obtain a positive electrode material. A battery element was constituted by the positive electrode material and the negative electrode material, and sealed in a battery can together with an electrolytic solution to produce a battery.
[0040]
Example 2
After mixing the above-described composition materials with a planetary mixer with the solvent removed, the mixture was charged and subjected to one-pass treatment with a twin-screw extrusion kneader so that the solid content was 83% (including 32 parts by weight of NMP). Thereafter, the kneaded material discharged from the biaxial extrusion kneader is further mixed and dispersed by a planetary mixer so that the dispersed solid content is 72.5% (including 27 parts by weight of NMP), and the adjusted positive electrode mixture paint Was applied to an aluminum foil having a thickness of 20 μm in the same manner as in Comparative Example 1 so as to have a total thickness of 180 μm to obtain a positive electrode material. A battery element was constituted by the positive electrode material and the negative electrode material, and sealed in a battery can together with an electrolytic solution to produce a battery.
[0041]
Example 3
After mixing the above-described composition materials with a planetary mixer with the solvent removed, the mixture was charged and subjected to one-pass treatment with a twin-screw extrusion kneader so that the solid content was 90% (including 17 parts by weight of NMP). Thereafter, the kneaded material discharged from the biaxial extrusion type kneader is further mixed and dispersed by a planetary mixer so that the dispersed solid content is 75.0% (including 35 parts by weight of NMP), and adjusted positive electrode mixture paint Was applied to an aluminum foil having a thickness of 20 μm in the same manner as in Comparative Example 1 so as to have a total thickness of 180 μm to obtain a positive electrode material. A battery element was constituted by the positive electrode material and the negative electrode material, and sealed in a battery can together with an electrolytic solution to produce a battery.
[0042]
Example 4
After mixing the above-described composition materials with a planetary mixer with the solvent removed, the mixture was charged and subjected to one-pass treatment with a twin screw extrusion kneader so that the solid content was 95% (including 8 parts by weight of NMP). Thereafter, the kneaded material discharged from the biaxial extrusion kneader is further mixed and dispersed by a planetary mixer so that the dispersed solid content is 75.0% (including 44 parts by weight of NMP), and the adjusted positive electrode mixture paint Was applied to an aluminum foil having a thickness of 20 μm in the same manner as in Comparative Example 1 so as to have a total thickness of 180 μm to obtain a positive electrode material. A battery element was constituted by the positive electrode material and the negative electrode material, and sealed in a battery can together with an electrolytic solution to produce a battery.
[0043]
Example 5
After mixing the above-described composition materials with a planetary mixer with the solvent removed, the mixture was charged and subjected to two-pass processing with a twin-screw extrusion kneader so that the solid content was 83% (including 32 parts by weight of NMP). Thereafter, a positive electrode mixture paint obtained by mixing and dispersing the kneaded material discharged from the biaxial extrusion type kneader to a dispersion solid content of 75.0% (including 20 parts by weight of NMP) with a planetary mixer was compared with Comparative Example 1. In the same manner as above, coating was performed on an aluminum foil having a thickness of 20 μm so as to have a total thickness of 180 μm to obtain a positive electrode material. A battery element was constituted by the positive electrode material and the negative electrode material, and sealed in a battery can together with an electrolytic solution to produce a battery.
[0044]
Example 6
After mixing the above-described composition materials with a planetary mixer and removing the solvent, the mixture is charged, the mixture is charged, and the solid content is 83% (including 32 parts by weight of NMP). did. Thereafter, the kneaded material discharged from the biaxial extrusion kneader is further mixed and dispersed by a planetary mixer so that the dispersed solid content is 72.5% (including 27 parts by weight of NMP), and the adjusted positive electrode mixture paint Was applied to an aluminum foil having a thickness of 20 μm in the same manner as in Comparative Example 1 so as to have a total thickness of 180 μm to obtain a positive electrode material. A battery element was constituted by the positive electrode material and the negative electrode material, and sealed in a battery can together with an electrolytic solution to produce a battery.
[0045]
As described above, the area density and the volume density were calculated for each secondary battery produced in the comparative example and each example. The area density and volume density of each secondary battery were calculated by punching the positive electrode material to a specific size, and measuring the weight and total thickness of the punched positive electrode material. Note that the volume density value varies depending on the degree of dispersion of the active material, even if the coating amount is the same, the weight and the total thickness are different. Specifically, when the dispersibility is improved, the active material is packed densely and thickly. Therefore, it can be used as an index indicating the degree of dispersibility.
[0046]
Moreover, about the positive electrode material used for the secondary battery of a comparative example and each Example, the abrasion loss of the coating film of a positive electrode active material layer was investigated. The wear loss of the coating film is measured by lowering the
[0047]
Abrasion loss (mg) = pre-test electrode specimen mass (mg)-pre-test electrode specimen mass (mg)
Wear loss (mmThree) = Wear weight loss (mg) / Wear powder density (g / cmThree)
[0048]
In addition, when rotation of the
[0049]
Abrasion loss (mg) = (Mass of electrode specimen before test (mg) −Mass of electrode specimen before test (mg)) × (100 / rotation speed of test)
Wear loss (mmThree) = Wear weight loss (mg) / Wear powder density (g / cmThree)
[0050]
Furthermore, the OCV rate was evaluated by charging the battery of Comparative Example and each Example to 4.25V under a constant current condition of 500 mA through aging for 12 hours in a general environment (25 ° C./60 RH%), Then, after 4 hours of charging, the voltage after 30 days was measured, and the voltage drop was regarded as the spontaneous discharge rate. If this value exceeded 10%, it was evaluated as defective and the ratio was calculated.
[0051]
The results of each survey described above are shown in Table 1, FIG. 4 and FIG.
[0052]
[Table 1]
As shown in Table 1 and FIG. 4, the secondary battery according to each example, which was mixed by the mixer and then kneaded by the kneader, was the second battery according to Comparative Example 1 in which the positive electrode mixture paint was adjusted only by the mixer. It can be confirmed that the wear loss is reduced and the OCV rate is reduced as compared to the secondary battery. Moreover, as shown in Table 1 and FIG. 5, it can confirm that the value of the volume density of the active material of the secondary battery which concerns on each Example is rising, From this, the secondary battery of each Example is It can be judged that the dispersibility is improved as compared with the secondary battery of the comparative example.
[0054]
【The invention's effect】
According to the method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention described above, the composition material excluding the solvent is used.Mix using a planetary mixer,Before adding solvent and mixing and dispersingOf the mixtureKneading the positive electrode mixture composition materialUsing a twin screw extrusion type kneaderDoneAfter kneading, a solvent is added and further mixed, and the positive electrode active material is dispersed using a planetary mixer.That is, by kneading the positive electrode mixture composition material before adding and mixing the solvent, the dispersibility of the active material in the positive electrode mixture paint can be improved and the capacity of the secondary battery can be increased. . Further, according to the method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention, the positive electrode mixture composition material is kneaded before adding and mixing the solvent, thereby strongly adsorbing the active material and the binder. Thus, the OCV rate of the secondary battery due to the dropping of the active material can be reduced.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a combined state of paddles of a biaxial extrusion type kneader.
FIG. 2 is a diagram for explaining a state of kneading with a paddle.
FIG. 3 is a perspective view of a turntable of a testing machine on which an electrode test piece is placed.
FIG. 4 is a characteristic diagram showing the relationship between wear loss and OCV rate.
FIG. 5 is a characteristic diagram showing a relationship between volume density and OCV rate.
[Explanation of symbols]
1 fuselage, 2 paddles, 3 major axis, 4 minor axis
Claims (4)
上記混合工程において混合された混合物を混練する混練工程と、
上記混練工程後に溶剤を加えてさらに混合しかつ正極活物質を分散させる混合分散工程と経て上記正極合剤塗料を調整し、
上記混合工程と上記混合分散工程とは、プラネタリーミキサーを用いて行い、
上記混練工程は、二軸押し出し型の混練装置を用いて行い、
上記組成材料は、少なくとも正極活物質粉末と、結合剤と、導電剤とを含有し、
上記正極活物質層は、摩耗減量が７５ｍｇ／１００回転以下である非水電解質二次電池の製造方法。A mixing step of mixing the composition material excluding the solvent from the positive electrode mixture paint applied to the positive electrode material to form the positive electrode active material layer;
A kneading step of kneading the mixture mixed in the mixing step;
After the kneading step, the solvent is added and further mixed and the positive electrode mixture paint is adjusted through a mixing and dispersing step of dispersing the positive electrode active material ,
The mixing step and the mixing and dispersing step are performed using a planetary mixer,
The kneading step is performed using a biaxial extrusion type kneading apparatus,
The composition material contains at least a positive electrode active material powder, a binder, and a conductive agent,
The said positive electrode active material layer is a manufacturing method of the nonaqueous electrolyte secondary battery whose wear loss is 75 mg / 100 rotation or less .
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| JP16292099A JP4277367B2 (en) | 1999-06-09 | 1999-06-09 | Method for producing non-aqueous electrolyte secondary battery |
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| JP16292099A JP4277367B2 (en) | 1999-06-09 | 1999-06-09 | Method for producing non-aqueous electrolyte secondary battery |
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| JP (1) | JP4277367B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US6939383B2 (en) * | 2002-05-03 | 2005-09-06 | 3M Innovative Properties Company | Method for making electrode |
| CN101043075B (en) | 2004-06-07 | 2010-12-08 | 松下电器产业株式会社 | Electrode plate of positive electrode for non-aqueous electrolyte secondary battery and manufacturing method thereof |
| JP2006269438A (en) * | 2006-04-28 | 2006-10-05 | Tdk Corp | Lithium-ion secondary battery |
| JP5655362B2 (en) * | 2010-04-28 | 2015-01-21 | 淺田鉄工株式会社 | Continuous production apparatus and continuous production method for electrode mixture-containing composition slurry for secondary battery |
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