JP2007080729A - Electrode for secondary battery, its manufacturing method, and secondary battery - Google Patents

Electrode for secondary battery, its manufacturing method, and secondary battery Download PDF

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JP2007080729A
JP2007080729A JP2005268476A JP2005268476A JP2007080729A JP 2007080729 A JP2007080729 A JP 2007080729A JP 2005268476 A JP2005268476 A JP 2005268476A JP 2005268476 A JP2005268476 A JP 2005268476A JP 2007080729 A JP2007080729 A JP 2007080729A
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electrode
secondary battery
active material
porous body
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Tamaki Miura
環 三浦
Junji Katamura
淳二 片村
Mikio Kawai
幹夫 川合
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Nissan Motor Co Ltd
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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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Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for a secondary battery capable of using a fine particulate active material having very fine particle sizes without substantially increasing the amount of a binder, increasing specific surface area of an electrode and preventing lowering of energy density by suppressing lowering in an active material ratio, and to provide the manufacturing method of the electrode. <P>SOLUTION: The fine particles of an electrode active material having an average particle size of ≤1 μm are formed in a lump-like porous body by using a technique such as coagulation, granulation, or sintering together with a conducting assistant such a carbon material if necessary, the porous body is used as the electrode active material and bound with the conductive assistant. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、例えば電気自動車や、ガソリンエンジンと電動モータによるハイブリット自動車などに好適に用いられる二次電池に係わり、詳しくは、このような二次電池の高出力、高容量化に寄与する二次電池用電極と、当該二次電池用電極の製造方法に関するものである。   The present invention relates to a secondary battery suitably used for, for example, an electric vehicle or a hybrid vehicle using a gasoline engine and an electric motor, and more specifically, a secondary battery that contributes to high output and high capacity of such a secondary battery. The present invention relates to a battery electrode and a method for producing the secondary battery electrode.

従来から、電気自動車やハイブリット自動車に用いられる二次電池として、高出力二次電池の開発が進んでいる。
このような二次電池の高出力化の手法としては、これまで、主として電極の薄膜化や高比表面積化などといった手法がとられてきており、例えば、ＢＥＴ比表面積が３ｍ２／ｇ以上のスピネル構造マンガン酸化物を正極に使用すること（特許文献１参照）、あるいは比表面積が４ｍ２／ｇ以上である電極（特許文献２参照）など、いくつかの提案がなされている。
特開平０７−０９７２１６号公報 特開平０７−１２２２６２号公報 Hitherto, high-power secondary batteries have been developed as secondary batteries used in electric vehicles and hybrid vehicles.
As a technique for increasing the output of such a secondary battery, techniques such as electrode thinning and a specific surface area have been mainly used so far. For example, the BET specific surface area is 3 m 2 / g or more. Several proposals have been made, such as using a spinel-structured manganese oxide for the positive electrode (see Patent Document 1) or an electrode having a specific surface area of 4 m 2 / g or more (see Patent Document 2).
Japanese Patent Application Laid-Open No. 07-097216 Japanese Patent Laid-Open No. 07-122262

この一方で、単に電極としての比表面積を大きくすることだけでなく、構成材料の粒子サイズを極めて小さくすることによる高比表面積化を目的とした活物質の小粒子化が高出力電池の実現に大きな効果があると期待されている。   On the other hand, not only increasing the specific surface area as an electrode, but also reducing the size of the active material for the purpose of increasing the specific surface area by making the particle size of the constituent material extremely small will realize a high-power battery. Expected to have significant effects.

しかしながら、上記のように、小粒子の電極活物質を用いた場合、電極化のために多くのバインダーや導電付与剤（導電助剤）を用いることが必要となり、それだけ活物質比率の低下を招くことになる。   However, as described above, when a small particle electrode active material is used, it is necessary to use a large number of binders and a conductivity-imparting agent (conducting aid) for forming an electrode, which leads to a decrease in the active material ratio. It will be.

活物質比率の低下は容量寄与分の低下だけではなく、溶媒使用量の増大、充填密度の低下など、全てにおいてエネルギー密度の低下につながる。
特に、電気自動車への適用を想定した場合、二次電池に対する高エネルギー密度への要求は一層高いものとなるため、小粒子化だけでは単セルの低容量化、セル数の増加の方向となり、より少ないセル数での高出力化と高容量を同時に実現することは難しいことになる。 A decrease in the active material ratio not only reduces the capacity contribution, but also leads to a decrease in energy density in all cases, such as an increase in the amount of solvent used and a decrease in packing density.
In particular, assuming application to electric vehicles, the demand for high energy density for secondary batteries will be even higher, so reducing the size of single cells alone will increase the number of cells. It is difficult to achieve high output and high capacity simultaneously with a smaller number of cells.

本発明は、従来の二次電池用電極における上記課題を解決すべくなされたものであって、その目的とするところは、バインダー量の大幅な増加を伴うことなく粒子径の極めて小さい微粒活物質を使用することができ、活物質比率の低下を抑制して、電極の高比表面積化と、エネルギー密度の低下を防止することができる二次電池用電極と、このような二次電池用電極の製造方法、さらにはこのような電極を用いた高性能の二次電池を提供することにある。   The present invention has been made to solve the above-mentioned problems in conventional secondary battery electrodes, and its object is to provide a finely divided active material having a very small particle diameter without a significant increase in the amount of binder. A secondary battery electrode capable of preventing the reduction of the active material ratio and preventing the increase of the specific surface area of the electrode and the reduction of the energy density, and such a secondary battery electrode. And a high-performance secondary battery using such an electrode.

本発明者らは、上記課題を解決すべく、二次電池の高出力化に対する効果が予測される粒子径の小さい電極活物質の利用方法について鋭意検討を繰り返した結果、微粒の電極活物質を、例えば凝集、造粒あるいは焼結などの手段によって、あらかじめ多孔質の塊状のものとすることにより、バインダー量を大幅に抑制することができ、電極の高比表面積化と活物質比率の維持、エネルギー密度の低下抑制が可能になることを見出し、本発明を完成するに到った。   In order to solve the above-mentioned problems, the present inventors have repeatedly conducted extensive studies on a method for using an electrode active material having a small particle diameter, which is expected to have an effect on increasing the output of a secondary battery. For example, by making a porous mass in advance by means such as agglomeration, granulation or sintering, the amount of the binder can be greatly suppressed, and the specific surface area of the electrode is increased and the active material ratio is maintained. The inventors have found that the reduction in energy density can be suppressed, and have completed the present invention.

本発明はこのような知見に基づくものであって、本発明の二次電池用電極は、特に、１μｍ以下の平均粒子径を備えた、例えばリチウムマンガン複合酸化物やリチウムニッケル複合酸化物、リチウムコバルト複合酸化物など、あるいは黒鉛や非晶質炭素などの電極活物質の微粒子により形成された塊状多孔質体と導電助剤を含み、この導電助剤が上記塊状多孔質体の表面や、塊状多孔質体内部の活物質粒子間に介在している構成としたことを特徴としている。   The present invention is based on such knowledge, and the electrode for a secondary battery according to the present invention particularly has an average particle diameter of 1 μm or less, for example, lithium manganese composite oxide, lithium nickel composite oxide, lithium A bulk porous body formed of fine particles of an electrode active material such as cobalt composite oxide or graphite or amorphous carbon and a conductive assistant, and the conductive assistant is used for the surface of the bulk porous body or the bulk The present invention is characterized in that it is interposed between the active material particles inside the porous body.

また、本発明の二次電池用電極の製造方法は、上記電極の製造に好適なものであって、微粒の電極活物質により形成された塊状多孔質体を導電助剤と共に順次適量ずつ、あるいは導電助剤によって被覆した状態の塊状多孔質体をバインダーが溶解した溶媒に投入して、これらを均一分散させ、これを集電箔上に塗布し、乾燥させるようにすることを特徴とする。   In addition, the method for producing an electrode for a secondary battery of the present invention is suitable for producing the above-mentioned electrode, and the massive porous body formed of the fine electrode active material is successively added together with the conductive auxiliary agent in appropriate amounts, or The massive porous body covered with the conductive auxiliary agent is put into a solvent in which a binder is dissolved, and these are uniformly dispersed, applied onto a current collector foil, and dried.

さらに、本発明の二次電池用電極の製造方法において、粗粒の電極活物質を用いる場合には、当該電極活物質を粗粒のままで導電助剤と共に、バインダーが溶解した溶媒が充填された湿式粉砕装置に投入し、これらを粉砕及び均一分散処理した後、集電箔上に塗布して、乾燥させることを特徴としている。   Furthermore, in the method for producing an electrode for a secondary battery of the present invention, when a coarse electrode active material is used, the electrode active material is left in a coarse particle and filled with a solvent in which a binder is dissolved together with a conductive additive. It is characterized in that it is put in a wet pulverizer, pulverized and uniformly dispersed, and then applied onto a current collector foil and dried.

そして、本発明の二次電池は、本発明の上記二次電池用電極を用いて構成されていることを特徴としている。   And the secondary battery of this invention is comprised using the said electrode for secondary batteries of this invention, It is characterized by the above-mentioned.

本発明によれば、平均粒子径が１μｍ以下の非常に小さい微粒電極活物質をあらかじめ塊状の多孔質体とした状態で使用するようにしているので、電極活物質粉末の取扱いが容易になるとと共に、微粒の電極活物質粒子をそのまま結着することにより電極化する場合に較べて、バインダー量を大幅に減らすことができ、樹脂比率増大に伴う活物質比率の低下及び電極抵抗の増加を抑制して、電極の高比表面化を図り、エネルギー密度の低下防止が可能となる。
そして、導電助剤が活物質粒子間に存在している状態を形成することによって、調整された塊状物はプレス時の力を緩和することができるようになり、構成微粒子の脱離、孤立粒子の発生、導電パスの欠落を防止することができる。 According to the present invention, an extremely small fine electrode active material having an average particle diameter of 1 μm or less is used in a state of being made into a massive porous body in advance, so that handling of the electrode active material powder becomes easy. The amount of binder can be greatly reduced compared to the case where electrodes are formed by binding fine electrode active material particles as they are, and the decrease in the active material ratio and the increase in electrode resistance due to the increase in the resin ratio are suppressed. Thus, it is possible to increase the specific surface of the electrode and prevent the energy density from being lowered.
Then, by forming a state in which the conductive auxiliary agent exists between the active material particles, the adjusted lump can relieve the force during pressing, and the detachment of the constituent fine particles, the isolated particles And the loss of the conductive path can be prevented.

上記二次電池用電極を製造するに際しては、微粒の電極活物質から形成された塊状多孔質体に導電助剤をあらかじめ被覆し、この状態でバインダーを含む溶媒中に投入し、均一に分散させてスラリーとし、このスラリーを集電箔上に塗布して、乾燥させるようにしているので、少量のバインダーによって塊状多孔質の電極活物質を導電助剤が被覆された状態に、均一に結着することができ、均一な組成を有し、比表面積及び活物質比率の高い二次電池用電極を得ることができる。   When manufacturing the electrode for a secondary battery, a bulky porous body formed of a fine electrode active material is coated beforehand with a conductive additive, and in this state, it is put into a solvent containing a binder and uniformly dispersed. The slurry is applied onto the current collector foil and dried, so that the massive porous electrode active material is evenly bound to the conductive assistant coated with a small amount of binder. Thus, a secondary battery electrode having a uniform composition and a high specific surface area and high active material ratio can be obtained.

また、塊状多孔質体と導電助剤をバインダーを含む溶媒中に順次投入していくことによって均一分散させたスラリーによっても、同様の特性を有し、微粒の電極活物質によって形成された塊状多孔質体の表面に導電助剤が分散した状態の二次電池用電極を得ることができる。   Also, a massive porous body formed of a fine electrode active material having the same characteristics can be obtained by uniformly dispersing a massive porous body and a conductive additive into a solvent containing a binder, by uniformly dispersing the slurry. An electrode for a secondary battery in which a conductive additive is dispersed on the surface of the material can be obtained.

そして、粗粒電極活物質を用いて上記のような二次電池用電極を製造するに際しては、粗粒電極活物質を導電助剤と共にバインダーが溶解した溶媒が充填された湿式粉砕装置に順次投入して、粉砕と共に均一分散処理したスラリーを集電箔上に塗布して、乾燥させるようにしているので、粉砕された活物質粒子が乾燥時に最凝集し、その周囲に導電助剤が分散した状態の電極を少量のバインダーによって結着することができ、均一な組成を有し、比表面積及び活物質比率の高い二次電池用電極を得ることができる。   Then, when manufacturing the secondary battery electrode using the coarse electrode active material as described above, the coarse electrode active material is sequentially charged into a wet pulverizer filled with a solvent in which a binder is dissolved together with a conductive additive. Then, since the slurry that has been uniformly dispersed along with the pulverization is applied onto the current collector foil and dried, the pulverized active material particles are most aggregated during the drying, and the conductive auxiliary agent is dispersed around them. The electrode in a state can be bound by a small amount of a binder, and a secondary battery electrode having a uniform composition and a high specific surface area and high active material ratio can be obtained.

以下、本発明の二次電池用電極及びその製造方法について、さらに詳細かつ具体的に説明する。   Hereinafter, the electrode for a secondary battery and the manufacturing method thereof of the present invention will be described in more detail and specifically.

本発明の二次電池用電極は、上記したように、１μｍ以下の平均粒子径を有する電極活性物質の微粉末（一次粒子）を例えば凝集させたり、バインダーなどを用いて造粒したり、さらには焼結等の手法を用いたりして塊状の多孔質体（二次粒子）とし、これを電極活物質として、導電助剤と共に用いたものであるが、このような塊状多孔質体を造粒する際の助剤としては、様々な成型用バインダーを使用することができる。   As described above, the electrode for a secondary battery of the present invention may be obtained by agglomerating fine particles (primary particles) of an electrode active substance having an average particle diameter of 1 μm or less, for example, by granulating using a binder or the like, Is a massive porous body (secondary particles) using a method such as sintering, and this is used as an electrode active material together with a conductive additive, but such a massive porous body is produced. As an auxiliary agent at the time of granulation, various molding binders can be used.

とりわけ、焼結法を用いる場合には、ポリビニルアルコール、ポリビニルブラール、ジエチレングリコールなど、アルコールに類する溶液を用いることによって造粒することが可能となる。とくに、ポリビニルアルコールなどを用いた場合には、脱バインダー時に適度な気孔が生成したり、発生した炭素が導電助剤的な機能を付与したりする効果も期待することができる。
なお、塊状多孔質体の造粒に際しては、上記導電助剤の一部又は全部を電極活物質粉末と共に造粒することも必要に応じて望ましい。 In particular, when a sintering method is used, granulation can be performed by using a solution similar to alcohol, such as polyvinyl alcohol, polyvinyl bral, and diethylene glycol. In particular, when polyvinyl alcohol or the like is used, it is possible to expect an effect that moderate pores are generated at the time of debinding, or that the generated carbon imparts a function as a conductive assistant.
When granulating the massive porous body, it is desirable if necessary to granulate a part or all of the conductive auxiliary agent together with the electrode active material powder.

本発明の二次電池用電極における電極活物質としては、正極活物質として、例えばリチウムマンガン複合酸化物、リチウムニッケル複合酸化物、リチウムコバルト複合酸化物、リチウム含有鉄酸化物、負極活物質として、例えば黒鉛や非晶質炭素を用いることが望ましく、これら電極活物質は、微粒子に調整し易く、平均粒子径が１μｍ以下の粒子からなる電極を容易に作ることができるようになる。
この他に、リチウム含有ニッケルコバルト酸化物やリチウム含有マンガンコバルト酸化物、リチウム含有ニッケルマンガン酸化物、リチウム含有ニッケルマンガンコバルト酸化物など多元素系の酸化物も正極活物質として使用することができ、負極活物質としては、上記した炭素材料の他に、スズ酸化物やケイ素酸化物などの金属酸化物、リチウムアルミニウム合金やリチウムスズ合金、リチウムケイ素合金などのリチウム合金などを使用することも可能である。 As an electrode active material in the secondary battery electrode of the present invention, as a positive electrode active material, for example, lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium-containing iron oxide, negative electrode active material, For example, it is desirable to use graphite or amorphous carbon. These electrode active materials can be easily adjusted to fine particles, and an electrode composed of particles having an average particle diameter of 1 μm or less can be easily produced.
In addition, multi-element oxides such as lithium-containing nickel cobalt oxide, lithium-containing manganese cobalt oxide, lithium-containing nickel manganese oxide, lithium-containing nickel manganese cobalt oxide can also be used as the positive electrode active material, As the negative electrode active material, in addition to the above-described carbon materials, metal oxides such as tin oxide and silicon oxide, lithium alloys such as lithium aluminum alloy, lithium tin alloy, and lithium silicon alloy can also be used. is there.

１μｍ以下の平均粒子径の電極活性物質から成る塊状多孔質体の平均粒子径、すなわち二次粒子径としては、１０μｍ以下とすることが望ましく、このようにすることによって緻密に充填された二次電池用電極を低いプレス圧で調整することができるようになる。   The average particle diameter of the massive porous body made of an electrode active material having an average particle diameter of 1 μm or less, that is, the secondary particle diameter is preferably 10 μm or less. The battery electrode can be adjusted with a low pressing pressure.

また、上記塊状多孔質体の比表面積としては、５ｍ２／ｇ以上、さらには１０ｍ２／ｇ以上であることが望ましく、これによって、結着用のバインダー量を確実に少なくすることができるようになると共に、得られる二次電池用電極の比表面積を大きくして、電極性能を向上させることが可能になる。
なお、本発明において「比表面積」とは、Ｎ２吸着ＢＥＴ法による比表面積を意味する。 The specific surface area of the massive porous body is preferably 5 m 2 / g or more, more preferably 10 m 2 / g or more, so that the amount of binder for binding can be reliably reduced. At the same time, the specific surface area of the obtained secondary battery electrode can be increased to improve the electrode performance.
In the present invention, the “specific surface area” means a specific surface area by the N 2 adsorption BET method.

本発明の二次電池用電極における導電助剤としては、カーボンブラックや黒鉛のような炭素材料を使用することができ、これによって電極内の導電性を向上させることができ、電池の出力を高めることができる。   As the conductive assistant in the secondary battery electrode of the present invention, a carbon material such as carbon black or graphite can be used, thereby improving the conductivity in the electrode and increasing the output of the battery. be able to.

上記カーボンブラックとしては、アセチレンブラック、ケッチェンブラック、ファーネスブラック等を用いることができ、黒鉛としては、鱗片状や繊維状のものを使用することができ、天然由来のものでも人造のものでも支障なく使用することができる。
なお、このような導電助剤の含有量としては、電極活物質１００重量部に対して、５〜３０重量部、さらには７〜１５重量部とすることが望ましい。 As the carbon black, acetylene black, ketjen black, furnace black, and the like can be used. As the graphite, scaly or fibrous materials can be used, which can be naturally derived or artificial. It can be used without.
In addition, as content of such a conductive support agent, it is desirable to set it as 5-30 weight part with respect to 100 weight part of electrode active materials, Furthermore, 7-15 weight part.

本発明の上記二次電池用電極を製造するには、種々の工程が考えられるが、まず第１に、平均粒子径が１μｍ以下の微粒電極活物質により形成された塊状多孔質体を用意し、この塊状多孔質電極活物質の表面に、上記したような導電助剤を被覆し、これを結着用のバインダーが溶解された溶媒中に少しずつ投入しながら、均一に分散させることによってスラリーとし、当該スラリーを集電箔上に塗布して、乾燥させる工程を採用することができる。   In order to produce the secondary battery electrode of the present invention, various processes are conceivable. First, a massive porous body made of a fine electrode active material having an average particle diameter of 1 μm or less is prepared. Then, the surface of the massive porous electrode active material is coated with a conductive aid as described above, and the slurry is uniformly dispersed while being gradually poured into a solvent in which the binding binder is dissolved. The slurry can be applied on the current collector foil and dried.

上記導電助剤の塊状多孔質体への被覆に際しては、例えばメカノフュージョン等、粉体の複合機を用いることが望ましく、これによって比較的大きな塊状多孔質体の周囲に小さな導電助剤粒子が均一に被覆された状態とすることができ、このような複合状態の塊状多孔質体を溶媒中に投入することになるため、より均一な分散を行うことができるようになる。もちろん分散剤等を用いた導電剤分散インクを添加することにより塊状多孔質体周辺に均一に存在することも被覆した状態と同じことと考える。
なお、上記導電助剤は、上記したように、その必要量の一部を塊状多孔質体の内部に介在させること、すなわち塊状多孔質体の造粒に際して、電極活物質に導電助剤を混合した粉末を造粒するようしてもよい。 When coating the conductive porous material on the massive porous body, it is desirable to use a powder compound machine such as mechanofusion, so that small conductive assistant particles are uniformly distributed around the relatively large massive porous body. Since the composite-like massive porous body is put into a solvent, more uniform dispersion can be performed. Of course, the presence of a conductive agent-dispersed ink using a dispersing agent or the like uniformly around the massive porous body is considered to be the same as the coated state.
In addition, as described above, the conductive auxiliary agent intervenes a part of the necessary amount inside the massive porous body, that is, when the massive porous body is granulated, the conductive active agent is mixed with the electrode active material. The powder may be granulated.

結着用のバインダーとしては、例えばフッ素ゴム（ＦＲ）、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリアクリロニトリル（ＰＡＮ）、ポリ塩化ビニル（ＰＶＣ）、エチレン‐プロピレン‐ジエン共重合体（ＥＰＤＭ）、ブタジエンゴム（ＢＲ）、スチレン‐ブタジエンゴム（ＳＢＲ）、セルロース、カルボキシメチルセルロース（ＣＭＣ）などを単独で、あるいはこれらの２種以上を任意に組み合わせて用いることができる。   As binders for binding, for example, fluorine rubber (FR), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyvinyl chloride (PVC), ethylene-propylene-diene copolymer (EPDM), butadiene rubber (BR) ), Styrene-butadiene rubber (SBR), cellulose, carboxymethylcellulose (CMC), etc., or any combination of two or more thereof can be used.

また、上記バインダーを溶解させるための溶媒としては、Ｎ−メチルピロリドン（ＮＭＰ）や水が代表的に用いられる。   Moreover, as a solvent for dissolving the binder, N-methylpyrrolidone (NMP) or water is typically used.

そして、スラリーを塗布する上記の集電箔としては、アルミニウムや銅、錫などの金属や、これらの合金、あるいはステンレス鋼等から成る金属箔を用いることができる。   And as said current collection foil which apply | coats a slurry, metal, such as metals, such as aluminum, copper, and tin, these alloys, or stainless steel, can be used.

上記のような活物質スラリーは、電極活物質の微粉末により形成された塊状多孔質体と導電助剤をバインダーが溶解した溶媒に順次少しずつ投入しながら、分散させることによっても得ることができ、このような電極活物質粒子が均一分散したスラリーを同様に集電箔上に塗布後、乾燥させることによって本発明の二次電池用電極を製造することができる。
なお、上記同様に、導電助剤を電極活物質と共に造粒した塊状多孔質体を用いることも可能なことは言うまでもない。 The active material slurry as described above can also be obtained by dispersing the massive porous body formed of fine powder of the electrode active material and the conductive assistant while gradually adding them to the solvent in which the binder is dissolved. The electrode for the secondary battery of the present invention can be produced by applying a slurry in which the electrode active material particles are uniformly dispersed on the current collector foil and then drying the slurry.
Needless to say, it is also possible to use a massive porous body obtained by granulating a conductive additive together with an electrode active material in the same manner as described above.

上記電極活物質としては、平均粒子径が１μｍ以下の所望の粒度にあらかじめ調整された状態のものを使用するばかりでなく、比較的粗粒のものを使用し、導電助剤と共にバインダーに混合しながら粉砕し、同時に分散させるようになすこともできる。
すなわち、粗粒の電極活物質と導電助剤を、バインダーが溶解した溶媒が充填された、例えばビーズミルのような湿式粉砕装置に投入して、上記電極活物質粒子の平均粒子径１μｍまでの粉砕と溶媒中への均一分散とを同時に行なうことによっても均一な活物質スラリーを得ることができる。 As the electrode active material, not only a material whose average particle size is adjusted to a desired particle size of 1 μm or less in advance, but also a relatively coarse material, which is mixed with a conductive auxiliary agent in a binder. It can also be pulverized and dispersed at the same time.
That is, a coarse electrode active material and a conductive assistant are put into a wet pulverization apparatus such as a bead mill filled with a solvent in which a binder is dissolved, and the electrode active material particles are pulverized to an average particle diameter of 1 μm. A uniform active material slurry can also be obtained by simultaneously carrying out and uniform dispersion in a solvent.

次に、当該スラリーを上記のような集電箔上に塗布し、乾燥させると、粉砕された活物質粒子が乾燥時に多孔質の塊状に再凝集し、この多孔質塊状電極活物質の周辺に配置された少量のバインダーによって導電助剤と共に結着された比表面積の大きな高出力の２次電池用電極が得られることになる。   Next, when the slurry is applied onto a current collector foil as described above and dried, the pulverized active material particles re-aggregate into a porous lump at the time of drying, and around the porous lump electrode active material. A high output secondary battery electrode having a large specific surface area bound together with the conductive additive by a small amount of the binder is obtained.

そして、本発明の上記二次電池用電極を正極、負極のいずれか一方、又は双方に採用することによって、非水電解液二次電池のような高出力特性を備えた二次電池を構成することができる。
このときの電解液としては、例えばプロピレンカーボネート（ＰＣ）、エチレンカーボネート（ＥＣ）、ジメチルカーボネート（ＤＭＣ）、メチルエチルカーボネート（ＭＥＣ）、ジエチルカーボネート（ＤＥＣ）、γ−ブチルラクトン（ＢＬ）などを単独もしくは
これらの２種以上を組み合わせた非水溶媒に、ＬｉＣｌ４、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６などの支持塩を溶解させたものを用いることができる。 And the secondary battery provided with the high output characteristic like a non-aqueous electrolyte secondary battery is comprised by employ | adopting the said electrode for secondary batteries of this invention for either a positive electrode, a negative electrode, or both. be able to.
Examples of the electrolyte solution used here include propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), and γ-butyl lactone (BL). Alternatively, a solution obtained by dissolving a supporting salt such as LiCl 4 , LiPF 6 , LiBF 4 , LiAsF 6 in a non-aqueous solvent in which two or more of these are combined can be used.

以下、本発明を実施例に基づいて具体的に説明する。なお、本発明は、これらの実施例のみに限定されるものではない。   Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited only to these Examples.

以下に示すように、実施例１は微粒の電極活物質により形成された塊状多孔質体にカノフュージョンを用いてカーボンブラックを被覆した例を示し、実施例２は湿式粉砕法によるスラリーを用いた場合の例を示したものである。
なお、比較例１は、上記実施例１に対する比較を示したものである。 As shown below, Example 1 shows an example in which carbon black is coated on a massive porous body formed of a fine electrode active material using canofusion, and Example 2 uses a slurry by a wet pulverization method. An example of the case is shown.
In addition, the comparative example 1 shows the comparison with the said Example 1. FIG.

（実施例１）
正極活物質として平均粒子径Ｄ５０（５０％累積粒子径）が１μｍのリチウムマンガン複合酸化物、導電助剤としてカーボンブラック、バインダーとしてポリフッ化ビニリデン（ＰＶＤＦ）、溶媒としてＮ−メチルピロリドン（ＮＭＰ）を使用した。
なお、電極組成は、正極活物質：バインダー：導電助剤＝８５：５：１０の質量比となるものとし、図１に示す工程に基づいて作製した。 Example 1
Lithium manganese composite oxide having an average particle diameter D50 (50% cumulative particle diameter) of 1 μm as a positive electrode active material, carbon black as a conductive additive, polyvinylidene fluoride (PVDF) as a binder, and N-methylpyrrolidone (NMP) as a solvent used.
Note that the electrode composition was a positive electrode active material: binder: conducting aid = 85: 5: 10 mass ratio, and was prepared based on the steps shown in FIG.

まず、上記正極活物質全量と導電助剤の半分を使用して、ポリビニルアルコールの存在下で混合してアルコールスラリーとし、流動層造粒装置を用いて造粒処理を行った。この造粒方法は転動流動層造粒装置を用いても構わないが乾燥まで行うものとする。造粒により得られた粉末の平均粒径が５μｍ程度となるように造粒処理を行い、塊状多孔質体とした。
なお、ＢＥＴ法に基づいてこの塊状多孔質体の比表面積を測定した結果、１０ｍ２／ｇであった。 First, using the total amount of the positive electrode active material and half of the conductive assistant, they were mixed in the presence of polyvinyl alcohol to obtain an alcohol slurry, and granulated using a fluidized bed granulator. This granulation method may use a rolling fluidized bed granulator, but it is performed until drying. Granulation was carried out so that the average particle size of the powder obtained by granulation was about 5 μm to obtain a massive porous body.
In addition, as a result of measuring the specific surface area of this block porous body based on BET method, it was 10 m < 2 > / g.

得られた塊状多孔質体と、残り半量の導電助剤をメカノフュージョン処理装置に投入し、表面被覆処理を施した。この処理によって、上記塊状多孔質体の表面に、細かなカーボンブラックが被覆された状態となっていることがＳＥＭ観察により確認された。   The obtained massive porous body and the remaining half of the conductive auxiliary agent were put into a mechanofusion treatment apparatus and subjected to a surface coating treatment. By this treatment, it was confirmed by SEM observation that the surface of the massive porous body was covered with fine carbon black.

次に、分散用ミキサーに高純度無水ＮＭＰ、次いでＰＶＤＦを投入し、これをＮＭＰ溶媒にＰＶＤＦを十分に溶解させた。   Next, high purity anhydrous NMP and then PVDF were added to the dispersing mixer, and PVDF was sufficiently dissolved in the NMP solvent.

この後、ＰＶＤＦが溶解したＮＭＰ溶媒に、先に得られた導電助剤で被覆された正極活物質粉末の塊状多孔質体を少しずつ投入することにより、ＰＶＤＦが溶解した溶媒になじませた。
上記塊状多孔質体がすべて投入された段階で、さらにＮＭＰ溶媒を適宜加えることによって粘度を調節し、スラリーとした。 Thereafter, the porous porous body of the positive electrode active material powder coated with the conductive auxiliary agent obtained previously was gradually added to the NMP solvent in which PVDF was dissolved, so that it was made to conform to the solvent in which PVDF was dissolved.
At the stage where all the massive porous bodies were charged, the viscosity was adjusted by adding an NMP solvent as appropriate to obtain a slurry.

得られたスラリーをアルミニウム箔上に塗布し、一定厚さのドクターブレードを用いて膜厚を調整したのち、ホットスターラー上で乾燥すると共に、ロールプレスにより密度調整することによって、二次電池用電極を得た。なお、この際のプレス圧は多孔体が粉砕されない程度とする必要があるため、装置荷重１０ｔ以下とした。
目視観察の結果、分散性、密着性含めて良好な電極状態であった。 The resulting slurry is applied onto an aluminum foil, and after adjusting the film thickness using a doctor blade of a certain thickness, it is dried on a hot stirrer, and the density is adjusted by a roll press, whereby a secondary battery electrode. Got. In addition, since it is necessary to make the press pressure in this case into the grade which a porous body does not grind | pulverize, it was set to 10 t or less of apparatus loads.
As a result of visual observation, it was a good electrode state including dispersibility and adhesion.

（実施例２）
正極活物質として、平均粒子径Ｄ５０（５０％累積粒子径）が１０μｍ程度のリチウムマンガン複合酸化物を選択し、これを湿式粉砕処理することによって所望の細粒となるようにした。
湿式粉砕処理としては、処理容器内に０．５ｍｍ径のジルコニア製ビーズを容積率で７０％充填し、一旦ＮＭＰを投入して、これを除去したのち、溶媒としての電池電極スラリー作製用の高純度無水ＮＭＰを投入した。その後、バインダーとしてＰＶＤＦを高純度無水ＮＭＰに溶解したものを投入して上記溶媒に溶解させた。 (Example 2)
As the positive electrode active material, a lithium manganese composite oxide having an average particle diameter D50 (50% cumulative particle diameter) of about 10 μm was selected, and this was subjected to a wet pulverization treatment so that desired fine particles were obtained.
In the wet pulverization treatment, 70% by volume of zirconia beads having a diameter of 0.5 mm is filled in a treatment vessel, and NMP is once introduced and removed, and then a high capacity for preparing battery electrode slurry as a solvent is used. Purity anhydrous NMP was added. Then, what melt | dissolved PVDF in high purity anhydrous NMP as a binder was thrown in, and it was made to melt | dissolve in the said solvent.

バインダーを含む溶媒が充填された処理容器内に、上記正極活物質と共に導電助剤としてのカーボンブラックを投入し、２時間湿式粉砕処理を行った。なお、電極組成は、正極活物質：バインダー：導電助剤＝８５：５：１０の質量比となる要に調整した。
得られたスラリーを溶媒で希釈、超音波で分散し、粒度分布を測定したところ、平均粒子径Ｄ５０が０．３μｍ以下、Ｄ９０は１μｍ以下となっていた。 Carbon black as a conductive additive was charged together with the positive electrode active material into a processing container filled with a solvent containing a binder, and wet pulverization was performed for 2 hours. In addition, the electrode composition was adjusted to the point where the mass ratio of positive electrode active material: binder: conductive aid = 85: 5: 10 was obtained.
When the obtained slurry was diluted with a solvent and dispersed with ultrasonic waves, and the particle size distribution was measured, the average particle diameter D50 was 0.3 μm or less, and D90 was 1 μm or less.

得られたスラリーをアルミニウム箔上に塗布し、一定厚さのドクターブレードを用いて膜厚を調整し、ホットスターラー上で乾燥すると共に、ロールプレスにより密度調整することによって、二次電池用電極を得た。   The obtained slurry was applied onto an aluminum foil, the film thickness was adjusted using a doctor blade having a certain thickness, dried on a hot stirrer, and the density was adjusted by a roll press, whereby the secondary battery electrode was Obtained.

目視観察の結果、分散性、密着性含めて良好な電極状態であった。
また、乾燥後の電極中には、１μｍ以下の活物質粒子がそれぞれ集合体（塊状多孔質体）を形成すると共に、導電助剤がその内部と周辺部に均一に存在している様子が電極の断面から観察された。集合体の平均粒子径は、ＳＥＭ観察から８〜１０μｍ程度であることが確認できた。 As a result of visual observation, it was a good electrode state including dispersibility and adhesion.
In addition, in the electrode after drying, active material particles of 1 μm or less each form an aggregate (bulky porous body), and the conductive assistant is present uniformly in and around the electrode. Observed from the cross section. The average particle diameter of the aggregate was confirmed to be about 8 to 10 μm from SEM observation.

（比較例１）
上記実施例１と同様に、正極活物質として平均粒子径Ｄ５０（５０％累積粒子径）が１μｍのリチウムマンガン複合酸化物、導電助剤としてカーボンブラック、バインダーとしてポリフッ化ビニリデン（ＰＶＤＦ）を使用した。
なお、電極組成は、正極活物質：バインダー：導電助剤＝８５：５：１０の質量比となるように電極を作製した。 (Comparative Example 1)
In the same manner as in Example 1, lithium manganese composite oxide having an average particle diameter D50 (50% cumulative particle diameter) of 1 μm was used as the positive electrode active material, carbon black was used as the conductive additive, and polyvinylidene fluoride (PVDF) was used as the binder. .
In addition, the electrode was produced so that electrode composition might become mass ratio of positive electrode active material: binder: conductive auxiliary agent = 85: 5: 10.

はじめに、分散用ミキサーに高純度無水ＮＭＰを投入したのち、ＰＶＤＦを投入し、ＮＭＰ溶媒に十分に溶解させた。
この後、当該溶媒に、上記活物質、導電助剤を少しずつ投入することにより、ＰＶＤＦが溶解した溶媒になじませた。
これら活物質及び導電助剤がすべて投入された段階で、さらにＮＭＰ溶媒を適宜加えることによって粘度を調節し、スラリーとした。 First, after adding high purity anhydrous NMP to the dispersing mixer, PVDF was added and sufficiently dissolved in the NMP solvent.
Thereafter, the active material and the conductive assistant were added little by little to the solvent to make it compatible with the solvent in which PVDF was dissolved.
At the stage when all of these active materials and conductive assistants were added, the viscosity was adjusted by adding an NMP solvent as appropriate to obtain a slurry.

得られたスラリーを同様にアルミニウム箔上に塗布し、一定厚さのドクターブレードを用いて膜厚を調整したのち、ホットスターラー上で乾燥すると共に、ロールプレスにより密度調整することによって、二次電池用電極を得た。
得られた電極層は、非常にもろく、電極の打ち抜き、裁断といった作業中において電極層のこぼれ、集電体からの剥離などが観察され、密着性は極めて弱い状態であった。 Similarly, the obtained slurry was applied on an aluminum foil, and after adjusting the film thickness using a doctor blade having a certain thickness, the slurry was dried on a hot stirrer and the density was adjusted by a roll press, whereby a secondary battery was obtained. An electrode was obtained.
The obtained electrode layer was very fragile, and during the operations such as punching and cutting of the electrode, spillage of the electrode layer, peeling from the current collector, etc. were observed, and the adhesion was extremely weak.

本発明の実施例１における電極の作製要領を示す工程図である。It is process drawing which shows the preparation points of the electrode in Example 1 of this invention.

Claims (10)

平均粒子径が１μｍ以下である電極活物質の微粒子により形成された塊状多孔質体と導電助剤を含み、当該導電助剤が上記塊状多孔質体の表面及び／又は内部の電極活物質微粒子間に介在していることを特徴とする二次電池用電極。   It includes a massive porous body formed of electrode active material fine particles having an average particle diameter of 1 μm or less and a conductive assistant, and the conductive assistant is between the surface and / or internal electrode active material fine particles of the massive porous body. An electrode for a secondary battery, characterized in that it is interposed in a battery. 上記電極活物質がリチウムマンガン複合酸化物、リチウムニッケル複合酸化物、リチウムコバルト複合酸化物、リチウム含有鉄酸化物、黒鉛及び非晶質炭素から成る群から選ばれる少なくとも１種であることを特徴とする請求項１に記載の二次電池用電極。   The electrode active material is at least one selected from the group consisting of lithium manganese composite oxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium-containing iron oxide, graphite, and amorphous carbon. The electrode for a secondary battery according to claim 1. 上記塊状多孔質体の平均粒子径が１０μｍ以下であることを特徴とする請求項１又は２に記載の二次電池用電極。   3. The electrode for a secondary battery according to claim 1, wherein an average particle diameter of the massive porous body is 10 μm or less. 上記塊状多孔質体の比表面積が５ｍ２／ｇ以上であることを特徴とする請求項１〜３のいずれか１つの項に記載の二次電池用電極。 The electrode for a secondary battery according to any one of claims 1 to 3, wherein the massive porous body has a specific surface area of 5 m 2 / g or more. 上記導電助剤がカーボンブラック及び／又は黒鉛を含む炭素材料であることを特徴とする請求項１〜４のいずれか１つの項に記載の二次電池用電極。   The electrode for a secondary battery according to any one of claims 1 to 4, wherein the conductive additive is a carbon material containing carbon black and / or graphite. 請求項１〜５のいずれか１つの項に記載の二次電池用電極を製造するに当たり、
上記導電助剤を被覆した状態の塊状多孔質体をバインダーが溶解した溶媒に投入し、分散させた後、集電箔上に塗布して、乾燥させることを特徴とする二次電池用電極の製造方法。 In manufacturing the electrode for a secondary battery according to any one of claims 1 to 5,
An electrode for a secondary battery, characterized in that the massive porous body coated with the conductive auxiliary agent is put into a solvent in which a binder is dissolved and dispersed, and then applied onto a current collector foil and dried. Production method. 請求項１〜５のいずれか１つの項に記載の二次電池用電極を製造するに当たり、
上記塊状多孔質体と上記導電助剤をバインダーが溶解した溶媒に投入し、分散させた後、集電箔上に塗布して、乾燥させることを特徴とする二次電池用電極の製造方法。 In manufacturing the electrode for a secondary battery according to any one of claims 1 to 5,
A method for producing an electrode for a secondary battery, characterized in that the massive porous body and the conductive additive are poured into a solvent in which a binder is dissolved and dispersed, and then applied onto a current collector foil and dried. 上記塊状多孔質体が導電助剤と共に造粒されていることを特徴とする請求項６又は７に記載の二次電池用電極の製造方法。   The method for producing an electrode for a secondary battery according to claim 6 or 7, wherein the massive porous body is granulated together with a conductive additive. 請求項１〜５のいずれか１つの項に記載の二次電池用電極を製造するに当たり、
平均粒子径が１μｍを超え１０μｍ以下の電極活物質と上記導電助剤をバインダーが溶解した溶媒が充填された湿式粉砕装置に投入し、上記電極活物質及び導電助剤を粉砕及び分散させた後、集電箔上に塗布して、乾燥させることを特徴とする二次電池用電極の製造方法。 In manufacturing the electrode for a secondary battery according to any one of claims 1 to 5,
After putting the electrode active material having an average particle diameter of more than 1 μm and not more than 10 μm and the conductive assistant into a wet pulverizer filled with a solvent in which a binder is dissolved, and pulverizing and dispersing the electrode active material and the conductive assistant A method for producing an electrode for a secondary battery, which is applied on a current collector foil and dried. 請求項１〜５のいずれか１つの項に記載の電極を用いて構成されていることを特徴とする二次電池。   A secondary battery comprising the electrode according to any one of claims 1 to 5.
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100928224B1 (en) * 2008-03-19 2009-11-24 한국전기연구원 Manufacturing method of nano active material electrode for energy storage device
JP2015185251A (en) * 2014-03-20 2015-10-22 Tdk株式会社 electrode and lithium ion secondary battery using the same
JP2015185252A (en) * 2014-03-20 2015-10-22 Tdk株式会社 electrode and lithium ion secondary battery using the same

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100928224B1 (en) * 2008-03-19 2009-11-24 한국전기연구원 Manufacturing method of nano active material electrode for energy storage device
JP2015185251A (en) * 2014-03-20 2015-10-22 Tdk株式会社 electrode and lithium ion secondary battery using the same
JP2015185252A (en) * 2014-03-20 2015-10-22 Tdk株式会社 electrode and lithium ion secondary battery using the same

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