JP6120087B2 - Method for forming protective layer on current collector body, current collector for lithium ion secondary battery, positive electrode for lithium ion secondary battery, and lithium ion secondary battery - Google Patents
Method for forming protective layer on current collector body, current collector for lithium ion secondary battery, positive electrode for lithium ion secondary battery, and lithium ion secondary battery Download PDFInfo
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- JP6120087B2 JP6120087B2 JP2013262779A JP2013262779A JP6120087B2 JP 6120087 B2 JP6120087 B2 JP 6120087B2 JP 2013262779 A JP2013262779 A JP 2013262779A JP 2013262779 A JP2013262779 A JP 2013262779A JP 6120087 B2 JP6120087 B2 JP 6120087B2
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- JP
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- Prior art keywords
- protective layer
- current collector
- ion secondary
- lithium ion
- conductive particles
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 239000011241 protective layer Substances 0.000 title claims description 127
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- 229910001416 lithium ion Inorganic materials 0.000 title claims description 59
- 238000000034 method Methods 0.000 title claims description 36
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- 229910052782 aluminium Inorganic materials 0.000 claims description 55
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 53
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- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 22
- 229910001887 tin oxide Inorganic materials 0.000 claims description 22
- 239000011254 layer-forming composition Substances 0.000 claims description 18
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Classifications
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、集電体本体への保護層形成方法、その保護層形成方法により形成された保護層を有するリチウムイオン二次電池用集電体、リチウムイオン二次電池用正極及びリチウムイオン二次電池に関するものである。 The present invention relates to a method for forming a protective layer on a current collector body, a current collector for a lithium ion secondary battery having a protective layer formed by the method for forming a protective layer, a positive electrode for a lithium ion secondary battery, and a lithium ion secondary It relates to batteries.
リチウムイオン二次電池の正極集電体には、電解塩による腐食に耐えるため、表面に安定な不動態膜を形成するＡｌなどの金属を使用するのが一般的である。例えばＡｌを集電体に用いた場合、その表面にＡｌ２Ｏ３、ＡｌＦ３等の不動態膜が形成される。Ａｌの集電体は表面に上記不動態膜が形成されるため、腐食されにくく、集電機能を保ちやすい。 In general, a positive electrode current collector of a lithium ion secondary battery uses a metal such as Al that forms a stable passive film on the surface in order to withstand corrosion by electrolytic salts. For example, when Al is used for the current collector, a passive film such as Al 2 O 3 or AlF 3 is formed on the surface thereof. Since the above passive film is formed on the surface of the Al current collector, it is not easily corroded and the current collecting function is easily maintained.
近年、リチウムイオン二次電池は、高電圧使用環境下（本明細書では４．３Ｖ以上の電圧で使用することを高電圧使用と定義する）でも良好に使用できることが望まれている。高電圧使用環境下では上記不動態膜が形成されていてもＡｌの集電体は徐々に腐食が進行し、Ａｌの集電体を有するリチウムイオン二次電池は保存特性が低下する懸念がある。 In recent years, it has been desired that lithium ion secondary batteries can be used satisfactorily even in a high voltage use environment (in this specification, use at a voltage of 4.3 V or higher is defined as high voltage use). Even under the high-voltage usage environment, even if the passive film is formed, the Al current collector is gradually corroded, and the lithium ion secondary battery having the Al current collector may be deteriorated in storage characteristics. .
高電圧使用環境下においてリチウムイオン二次電池の保存特性を維持するために、集電体に保護層を形成する検討がされている。例えば、イオンスパッタ法や真空蒸着法などのドライプロセスによって保護層を形成することが検討されている。また、有機溶剤を用いたウエットプロセスで保護層を形成することも検討されている。 In order to maintain the storage characteristics of the lithium ion secondary battery under a high voltage use environment, studies are being made to form a protective layer on the current collector. For example, forming a protective layer by a dry process such as an ion sputtering method or a vacuum deposition method has been studied. In addition, the formation of a protective layer by a wet process using an organic solvent has been studied.
ドライプロセスによる成膜は、成膜時の膜応力が集電体に残りやすく、成膜を大面積化する上では好ましくない。またウエットプロセスに関して、近年多くの産業分野において、安全性や作業性の観点より、無溶剤化への要求が高まっている。この保護層についても、環境に優しい水系溶剤を用いて保護層を形成することが検討されている。例えば特許文献１には、ポリテトラフルオロエチレン（ＰＴＦＥ）の水分散体に導電性カーボンフィラーを加えてペーストを作成し、そのペーストをアルミニウム箔からなる集電体に塗布して集電体に保護層を形成する方法が開示されている。 Film formation by a dry process is not preferable in that the film stress at the time of film formation tends to remain on the current collector and the film formation is increased. With regard to the wet process, in recent years, in many industrial fields, there has been an increasing demand for solvent-free from the viewpoint of safety and workability. Regarding this protective layer, it has been studied to form a protective layer using an environmentally friendly aqueous solvent. For example, in Patent Document 1, a conductive carbon filler is added to an aqueous dispersion of polytetrafluoroethylene (PTFE) to create a paste, and the paste is applied to a current collector made of aluminum foil to protect the current collector. A method of forming a layer is disclosed.
水系溶剤を用いて保護層を形成する場合は、一般的に導電性粒子は水系溶剤に分散しにくい。そのため分散性の良い導電性粒子を用いる、水系溶剤に分散剤や有機溶剤を入れるなどによって、導電性粒子の分散性を向上させることが行われている。 When the protective layer is formed using an aqueous solvent, the conductive particles are generally difficult to disperse in the aqueous solvent. Therefore, the dispersibility of the conductive particles is improved by using conductive particles with good dispersibility or by adding a dispersant or an organic solvent into an aqueous solvent.
しかしながら一度安定的に分散する状態にした導電性粒子の水分散体に他の物質を混合すると、導電性粒子の分散性が悪くなり、導電性粒子が凝集することがある。保護層形成用組成物内の導電性粒子の分散性が悪いと保護層形成用組成物の集電体への塗工が難しくなる。 However, if other substances are mixed with the aqueous dispersion of conductive particles once stably dispersed, the dispersibility of the conductive particles may deteriorate and the conductive particles may aggregate. When the dispersibility of the conductive particles in the protective layer-forming composition is poor, it becomes difficult to apply the protective layer-forming composition to the current collector.
本発明は、このような事情に鑑みて為されたものであり、特定の導電性粒子の水分散体を用いる集電体本体への保護層形成方法、その保護層形成方法を経て形成された保護層を有するリチウムイオン二次電池用集電体、リチウムイオン二次電池用正極及びリチウムイオン二次電池を提供することを目的とする。 The present invention has been made in view of such circumstances, and was formed through a method for forming a protective layer on a current collector body using an aqueous dispersion of specific conductive particles, and a method for forming the protective layer. It aims at providing the collector for lithium ion secondary batteries which has a protective layer, the positive electrode for lithium ion secondary batteries, and a lithium ion secondary battery.
本発明者等が、アンチモンドープ酸化スズ（ＡＴＯ）又はアンチモンドープ酸化スズ（ＡＴＯ）被覆酸化物からなる導電性粒子の水分散体に水系バインダー含有水を混合して保護層を作成する検討を行ったところ、混合によって導電性粒子が凝集してしまい、集電体に保護層形成用組成物を塗布することが困難であることがわかった。本発明者等が鋭意検討した結果、上記導電性粒子の水分散体を攪拌機で１０００ｒｐｍ以上の回転数で攪拌しながら導電性粒子の水分散体に水系バインダー含有水を添加することによって、保護層形成用組成物内の導電性粒子の凝集を抑制できることを見いだした。 The inventors of the present invention have studied to create a protective layer by mixing water-containing binder-containing water with an aqueous dispersion of conductive particles made of antimony-doped tin oxide (ATO) or antimony-doped tin oxide (ATO) coating oxide. As a result, it was found that the conductive particles aggregate due to the mixing, and it is difficult to apply the protective layer-forming composition to the current collector. As a result of intensive investigations by the present inventors, a protective layer is obtained by adding water-based binder-containing water to the aqueous dispersion of conductive particles while stirring the aqueous dispersion of conductive particles with a stirrer at a rotation speed of 1000 rpm or more. It has been found that aggregation of conductive particles in the forming composition can be suppressed.
すなわち、本発明の集電体本体への保護層形成方法は、アンチモンドープ酸化スズ（ＡＴＯ）又はアンチモンドープ酸化スズ（ＡＴＯ）被覆酸化物からなる導電性粒子の水分散体を攪拌機で１０００ｒｐｍ以上の回転数で攪拌しながら上記導電性粒子の水分散体に水系バインダー含有水を添加することによって、導電性粒子の水分散体と水系バインダー含有水とを混合して保護層形成用組成物を調製する保護層形成用組成物調製工程と、アルミニウム箔からなる集電体本体に保護層形成用組成物を塗布し、乾燥して集電体本体の表面に保護層を形成する保護層形成工程と、を有することを特徴とする。 That is, the method for forming a protective layer on the current collector main body of the present invention is a method in which an aqueous dispersion of conductive particles made of antimony-doped tin oxide (ATO) or antimony-doped tin oxide (ATO) -coated oxide is stirred at 1000 rpm or more with a stirrer. Prepare a protective layer-forming composition by mixing the aqueous dispersion of conductive particles and the aqueous binder-containing water by adding aqueous binder-containing water to the aqueous dispersion of conductive particles while stirring at a rotational speed. A protective layer forming composition preparation step, and a protective layer forming step of applying the protective layer forming composition to the current collector body made of aluminum foil and drying to form a protective layer on the surface of the current collector body; It is characterized by having.
水系バインダー含有水に含まれる水系バインダーは、ポリアクリル酸（ＰＡＡ）であることが好ましい。 The aqueous binder contained in the aqueous binder-containing water is preferably polyacrylic acid (PAA).
導電性粒子と水系バインダー含有水に含まれる水系バインダーとの配合比は、固形分の質量比で導電性粒子：水系バインダー＝８０：２０〜９９．９：０．１であることが好ましい。 The compounding ratio of the conductive particles and the aqueous binder contained in the aqueous binder-containing water is preferably conductive particles: aqueous binder = 80: 20 to 99.9: 0.1 based on the mass ratio of the solid content.
導電性粒子は、アンチモンドープ酸化スズ（ＡＴＯ）であることが好ましい。 The conductive particles are preferably antimony-doped tin oxide (ATO).
導電性粒子は針状であることが好ましい。 The conductive particles are preferably acicular.
本発明の集電体本体への保護層形成方法は、保護層形成工程の前に、アルミニウム箔を８０℃〜１６０℃で１時間以上保持する熱処理を行って熱処理済アルミニウム箔を得るアルミニウム箔の熱処理工程をさらに有することが好ましく、保護層形成工程のアルミニウム箔は熱処理済みアルミニウム箔であることが好ましい。 The method for forming a protective layer on the current collector main body of the present invention is a method for forming a heat-treated aluminum foil by performing a heat treatment for holding the aluminum foil at 80 ° C. to 160 ° C. for 1 hour or longer before the protective layer forming step. It is preferable to further have a heat treatment step, and the aluminum foil in the protective layer forming step is preferably a heat-treated aluminum foil.
本発明のリチウムイオン二次電池用集電体は、アルミニウム箔からなる集電体本体と、集電体本体の上に配置された上記集電体本体への保護層形成方法を経て形成された保護層と、からなることを特徴とする。 The current collector for a lithium ion secondary battery of the present invention was formed through a current collector body made of aluminum foil and a method for forming a protective layer on the current collector body disposed on the current collector body. And a protective layer.
本発明のリチウムイオン二次電池用正極は、上記リチウムイオン二次電池用集電体を有することを特徴とする。 The positive electrode for lithium ion secondary batteries of this invention has the said collector for lithium ion secondary batteries, It is characterized by the above-mentioned.
本発明のリチウムイオン二次電池は、上記リチウムイオン二次電池用正極を有することを特徴とする。 The lithium ion secondary battery of this invention has the said positive electrode for lithium ion secondary batteries, It is characterized by the above-mentioned.
本発明の集電体本体への保護層形成方法によれば、特定の導電性粒子の水分散体を用いる保護層形成用組成物を集電体本体に塗工でき、厚みの均一な保護層をアルミニウム箔上に形成できる。 According to the method for forming a protective layer on a current collector body of the present invention, a protective layer forming composition using an aqueous dispersion of specific conductive particles can be applied to the current collector body, and the protective layer has a uniform thickness. Can be formed on an aluminum foil.
以下に、本発明を実施するための形態を説明する。なお、特に断らない限り、本明細書に記載された数値範囲「ａ〜ｂ」は、下限ａおよび上限ｂをその範囲に含む。そして、これらの上限値および下限値、ならびに実施例中に列記した数値も含めてそれらを任意に組み合わせることで数値範囲を構成し得る。さらに数値範囲内から任意に選択した数値を上限、下限の数値とすることができる。 Below, the form for implementing this invention is demonstrated. Unless otherwise specified, the numerical range “ab” described herein includes the lower limit “a” and the upper limit “b”. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from the numerical value range can be used as upper and lower numerical values.
＜集電体本体への保護層形成方法＞
本発明の集電体本体への保護層形成方法は、保護層形成用組成物調製工程と、保護層形成工程とを有する。
<Method for forming protective layer on current collector body>
The method for forming a protective layer on the current collector body of the present invention includes a protective layer forming composition preparing step and a protective layer forming step.
保護層形成用組成物調製工程は、アンチモンドープ酸化スズ（ＡＴＯ）又はアンチモンドープ酸化スズ（ＡＴＯ）被覆酸化物からなる導電性粒子の水分散体を攪拌機で１０００ｒｐｍ以上の回転数で攪拌しながら上記導電性粒子の水分散体に水系バインダー含有水を添加することによって、導電性粒子の水分散体と水系バインダー含有水とを混合して保護層形成用組成物を調製する。 The protective layer-forming composition preparation step includes the steps of stirring an aqueous dispersion of conductive particles made of antimony-doped tin oxide (ATO) or antimony-doped tin oxide (ATO) -coated oxide with a stirrer at a rotation speed of 1000 rpm or more. By adding aqueous binder-containing water to the aqueous dispersion of conductive particles, the aqueous dispersion of conductive particles and the aqueous binder-containing water are mixed to prepare a composition for forming a protective layer.
導電性粒子は、アンチモンドープ酸化スズ（ＡＴＯ）又はアンチモンドープ酸化スズ（ＡＴＯ）被覆酸化物からなる。 The conductive particles are made of antimony-doped tin oxide (ATO) or antimony-doped tin oxide (ATO) coating oxide.
ＡＴＯにおいては、酸化スズにアンチモンがドープされている。酸化スズは、大気中の酸素、電解液及び電解塩に耐性があり、また高電圧においてもその耐性を良好に維持する。また酸化スズは耐酸化性にも優れている。ＡＴＯは、酸化スズの特性を有しながら、さらに酸化スズに比べて大幅に導電性が向上している。アンチモンのドープ量は特に限定されない。ＡＴＯとして、例えば、酸化スズに対してアンチモンを０．１質量％〜２質量％ドープしたものが使用できる。 In ATO, tin oxide is doped with antimony. Tin oxide is resistant to oxygen, electrolytes and electrolyte salts in the atmosphere, and maintains its resistance well even at high voltages. Tin oxide is also excellent in oxidation resistance. While ATO has the characteristics of tin oxide, its conductivity is significantly improved compared to tin oxide. The amount of antimony doped is not particularly limited. As ATO, what doped 0.1 to 2 mass% of antimony with respect to tin oxide can be used, for example.
ＡＴＯ粒子を含む材料として、具体的には、例えば、石原産業株式会社製ＳＮ−１００Ｐ（球状粉末）、ＳＮ−１００Ｄ（球状水分散体）、ＳＮＳ−１０Ｍ（球状ＭＥＫ分散体）、ＦＳ−１０Ｐ（針状粉末）、ＦＳ−１０Ｄ（針状水分散体）、三菱マテリアル電子化成株式会社製Ｔ−１（球状粉末）、ＴＤＬ−１（球状水分散体）が挙げられる。 Specific examples of materials containing ATO particles include SN-100P (spherical powder), SN-100D (spherical water dispersion), SNS-10M (spherical MEK dispersion), and FS-10P manufactured by Ishihara Sangyo Co., Ltd. (Acicular powder), FS-10D (acicular water dispersion), T-1 (spherical powder), TDL-1 (spherical water dispersion) manufactured by Mitsubishi Materials Electronics Chemical Co., Ltd.
アンチモンドープ酸化スズ（ＡＴＯ）被覆酸化物としては、例えば、ＡＴＯで表面が被覆された酸化チタン、ＡＴＯで表面が被覆された酸化ジルコニウム、ＡＴＯで表面が被覆された酸化セリウムが挙げられる。ＡＴＯで表面が被覆された酸化物は、ＡＴＯの導電性が高いため、被覆前の酸化物よりも導電性が向上する。 Examples of the antimony-doped tin oxide (ATO) -coated oxide include titanium oxide whose surface is coated with ATO, zirconium oxide whose surface is coated with ATO, and cerium oxide whose surface is coated with ATO. Since the oxide whose surface is coated with ATO has high conductivity of ATO, the conductivity is improved as compared with the oxide before coating.
ＡＴＯ被覆酸化物粒子として、具体的には、例えば、石原産業株式会社製ＥＴ-３００Ｗ（球状ＡＴＯ被覆ＴｉＯ２）、ＥＴ-５００Ｗ（球状ＡＴＯ被覆ＴｉＯ２）、ＥＴ−６００Ｗ（球状ＡＴＯ被覆ＴｉＯ２）、ＦＴ−１０００（針状ＡＴＯ被覆ＴｉＯ２）、ＦＴ−２０００（針状ＡＴＯ被覆ＴｉＯ２）、ＦＴ−３０００（針状ＡＴＯ被覆ＴｉＯ２）が挙げられる。 As ATO coating oxide particles, specifically, for example, Ishihara Sangyo Kaisha Ltd. ET-300 W (spherical ATO coating TiO 2), ET-500 W (spherical ATO coating TiO 2), ET-600W (spherical ATO coated TiO 2 ), FT-1000 (acicular ATO-coated TiO 2 ), FT-2000 (acicular ATO-coated TiO 2 ), and FT-3000 (acicular ATO-coated TiO 2 ).
導電性粒子は、ＡＴＯ粒子であることが好ましい。ＡＴＯ粒子は、粒子表面だけでなく、粒子内部も電子伝導性が高いＡＴＯで構成されている。そのため、ＡＴＯ粒子は、ＡＴＯ被覆酸化物粒子に比べて電子伝導性が高く、粉体の体積抵抗値で比較すればＡＴＯ粒子の粉体の体積抵抗値は、ＡＴＯ被覆酸化物粒子の粉体の体積抵抗値の約１／３〜１／２である。 The conductive particles are preferably ATO particles. ATO particles are composed of ATO having high electron conductivity not only on the particle surface but also inside the particles. Therefore, the ATO particles have higher electron conductivity than the ATO-coated oxide particles, and the volume resistance value of the powder of the ATO particles is the same as that of the powder of the ATO-coated oxide particles. It is about 1/3 to 1/2 of the volume resistance value.
集電体本体に上記導電性粒子を含む保護層が形成されると、高電圧使用環境下であっても集電体本体が電解液などから良好に保護される。 When the protective layer containing the conductive particles is formed on the current collector body, the current collector body is well protected from the electrolyte solution and the like even under a high voltage use environment.
導電性粒子の形状は、特に限定されないが、例えば、球状形状、針状形状が挙げられる。 The shape of the conductive particles is not particularly limited, and examples thereof include a spherical shape and a needle shape.
導電性粒子が球状形状である場合は、導電性粒子の一次粒子の平均粒径Ｄ５０は、５０ｎｍ以下が好ましい。一次粒子の平均粒径Ｄ５０が、５０ｎｍ以下であれば、水分散体において、導電性粒子を良好に分散させることができる。平均粒径Ｄ５０は、電子顕微鏡による観察画像より２０個〜３０個の粒子の粒径を直接計測し、その平均値を取ることで求めることができる。 When the conductive particles are spherical shape, an average particle diameter D 50 of the primary particles of the conductive particles they are preferably not more than 50nm. The average particle diameter D 50 of the primary particle is equal to or 50nm or less, in an aqueous dispersion, the conductive particles can be well dispersed. The average particle diameter D 50 is the particle size of 20 to 30 amino particle from observation image by an electron microscope directly measures the can be determined by taking the average value thereof.
また導電性粒子の分散粒径Ｄ５０は、２００ｎｍ以下であることが好ましく、１００ｎｍ程度であることがさらに好ましい。分散粒径Ｄ５０は、液体中の導電性粒子のキュムラント平均粒子径のことである。キュムラント平均粒子径とは、液体中の導電性粒子の粒径を動的光散乱法により測定し、得られたデータをＣｕｍｕｌａｎｔ法により解析して算出した数値である。導電性粒子の分散粒径Ｄ５０が２００ｎｍより大きいと、導電性粒子が顕著に凝集しているおそれがあり、保護層形成用組成物を集電体本体に塗工しにくく、また保護層の厚みが厚くなりすぎる。 The dispersion particle diameter D 50 of the conductive particles is preferably 200nm or less, and still more preferably about 100 nm. Dispersion particle diameter D 50 is that the cumulant average particle diameter of the conductive particles in a liquid. The cumulant average particle diameter is a numerical value calculated by measuring the particle diameter of conductive particles in a liquid by a dynamic light scattering method and analyzing the obtained data by a Cumulant method. And 200nm is greater than the dispersion particle diameter D 50 of the conductive particles, there is a possibility that the conductive particles are significantly agglomerate, the protective layer forming composition hardly applied to the current collector body and of the protective layer The thickness becomes too thick.
導電性粒子が針状形状である場合は、導電性粒子の配合量を球状形状の導電性粒子に比べて少なくできる。針状形状の導電性粒子は、保護層に含有される導電性粒子の個数が少なくても、保護層中に長い導電パスを作成することができる。そのため球状形状の導電性粒子に比べて少ない配合量で針状形状の導電性粒子は同様の導電性を確保できる。 When the conductive particles are needle-shaped, the amount of the conductive particles can be reduced compared to the spherical conductive particles. The acicular conductive particles can create a long conductive path in the protective layer even if the number of conductive particles contained in the protective layer is small. Therefore, the needle-shaped conductive particles can ensure the same conductivity with a smaller blending amount than the spherical conductive particles.
針状形状の導電性粒子においては、短軸が３００ｎｍ以下であることが好ましい。針状形状の導電性粒子の短軸が３００ｎｍより大きいと、粒子そのものが非常に大きくなり、比重で沈殿しやすくなって分散安定性が保てなくなるおそれがある。例えば、針状形状の導電性粒子においては、長軸が０．２μｍ〜２０μｍ、短軸が０．０１μｍ〜０．３μｍ、アスペクト比（長軸／短軸）が１０〜３０であることが好ましい。 In acicular conductive particles, the minor axis is preferably 300 nm or less. If the short axis of the needle-shaped conductive particles is larger than 300 nm, the particles themselves become very large, and are likely to precipitate due to their specific gravity, which may make it impossible to maintain dispersion stability. For example, in the needle-shaped conductive particles, the major axis is preferably 0.2 μm to 20 μm, the minor axis is 0.01 μm to 0.3 μm, and the aspect ratio (major axis / minor axis) is preferably 10 to 30. .
針状形状の導電性粒子を含む材料として、具体的には、例えば、石原産業株式会社製ＦＳ−１０Ｐ（針状ＡＴＯ粉末）、ＦＳ−１０Ｄ（針状ＡＴＯ水分散体）ＦＴ−１０００（針状ＡＴＯ被覆ＴｉＯ２）、ＦＴ−２０００（針状ＡＴＯ被覆ＴｉＯ２）、ＦＴ−３０００（針状ＡＴＯ被覆ＴｉＯ２）が挙げられる。 Specific examples of materials containing needle-shaped conductive particles include FS-10P (needle-shaped ATO powder) and FS-10D (needle-shaped ATO water dispersion) FT-1000 (needle) manufactured by Ishihara Sangyo Co., Ltd. ATO-coated TiO 2 ), FT-2000 (needle-shaped ATO-coated TiO 2 ), and FT-3000 (needle-shaped ATO-coated TiO 2 ).
保護層形成用組成物調製工程において、上記導電性粒子の水分散体を使用する。水分散体とは、水に導電性粒子が分散しているものをいう。ここで分散とは、水の中に導電性粒子が微粒子の状態で一様に散在していることをいう。 In the protective layer forming composition preparing step, the aqueous dispersion of the conductive particles is used. The water dispersion means a material in which conductive particles are dispersed in water. Here, dispersion means that conductive particles are uniformly dispersed in water in the form of fine particles.
水分散体において、水は、蒸留水やイオン交換水など、不純物を取り除いたものが好ましい。また水分散体における水にはアルコールが添加されていてもよい。アルコールとしては、例えば、メタノール、エタノール、イソプロパノールが挙げられる。水にアルコールを添加する場合は、水とアルコールの配合比は、質量比で水：アルコール＝９９．９：０．１〜５０：５０であることが好ましい。アルコールの配合比が多くなりすぎると、水分散体中の導電性粒子の分散安定性が低下して、導電性粒子が凝集、沈殿を起こしやすくなるおそれがある。 In the aqueous dispersion, the water is preferably water from which impurities have been removed, such as distilled water or ion exchange water. Alcohol may be added to the water in the aqueous dispersion. Examples of the alcohol include methanol, ethanol, and isopropanol. When adding alcohol to water, it is preferable that the compounding ratio of water and alcohol is water: alcohol = 99.9: 0.1-50: 50 by mass ratio. If the blending ratio of the alcohol is too large, the dispersion stability of the conductive particles in the aqueous dispersion may decrease, and the conductive particles may easily aggregate and precipitate.
アンチモンドープ酸化スズ（ＡＴＯ）又はアンチモンドープ酸化スズ（ＡＴＯ）被覆酸化物からなる導電性粒子は、酸化物であるので、表面に水酸基を持つ。上記導電性粒子はそのため親水性が高い。上記導電性粒子を水と混合すれば、水分散体とすることができる。またさらに安定的な分散状態にするために、水分散体は分散剤を含有していてもよい。 Since the conductive particles made of antimony-doped tin oxide (ATO) or antimony-doped tin oxide (ATO) -coated oxide are oxides, they have a hydroxyl group on the surface. Therefore, the conductive particles are highly hydrophilic. An aqueous dispersion can be obtained by mixing the conductive particles with water. In order to obtain a more stable dispersion state, the aqueous dispersion may contain a dispersant.
導電性粒子の水分散体における導電性粒子の含有量は、水分散体全体を１００質量％としたときに、１．０質量％以上４０．０質量％以下であることが好ましく、３．０質量％以上３０．０質量％以下であることがさらに好ましい。導電性粒子の含有量が１．０質量％より少ないと、水の含有量が多いため、塗工性が悪化し、また乾燥効率も低下するおそれがある。導電性粒子の含有量が４０．０質量％より多いと、導電性粒子の分散安定性を維持することが難しくなり、導電性粒子が凝集、沈殿を起こしやすくなるおそれがある。 The content of the conductive particles in the aqueous dispersion of conductive particles is preferably 1.0% by mass or more and 40.0% by mass or less when the entire aqueous dispersion is 100% by mass. More preferably, it is at least 3% by mass and no more than 30.0% by mass. If the content of the conductive particles is less than 1.0% by mass, the water content is large, so that the coatability is deteriorated and the drying efficiency may be lowered. When the content of the conductive particles is more than 40.0% by mass, it is difficult to maintain the dispersion stability of the conductive particles, and the conductive particles may easily aggregate and precipitate.
水系バインダー含有水は、水に水系バインダーを溶解又は分散させたものである。 The aqueous binder-containing water is obtained by dissolving or dispersing an aqueous binder in water.
水系バインダー含有水における水は、蒸留水やイオン交換水など、不純物を取り除いたものが好ましい。また水系バインダー含有水における水にはアルコールが添加されていてもよい。アルコールとしては、例えば、メタノール、エタノール、イソプロパノールが挙げられる。水にアルコールを添加する場合は、水とアルコールの配合比は、質量比で水：アルコール＝９９．９：０．１〜５０：５０が好ましい。アルコールの配合比が多くなりすぎると、水系バインダー含有水における水系バインダーの分散安定性が低下し、水系バインダーが凝集、沈殿を起こしやすくなるおそれがある。 The water in the aqueous binder-containing water is preferably water from which impurities such as distilled water or ion exchange water have been removed. Alcohol may be added to the water in the aqueous binder-containing water. Examples of the alcohol include methanol, ethanol, and isopropanol. When adding alcohol to water, the mixing ratio of water and alcohol is preferably water: alcohol = 99.9: 0.1 to 50:50 in terms of mass ratio. If the blending ratio of the alcohol is too large, the dispersion stability of the aqueous binder in the aqueous binder-containing water is lowered, and the aqueous binder may easily aggregate and precipitate.
水系バインダーとしては、水溶性バインダー、水分散性バインダーが使用できる。水溶性バインダーとして、例えば、ポリアクリル酸（ＰＡＡ）、ポリエチレングリコール（ＰＥＧ）が挙げられる。水分散性バインダーとして、アクリルースチレン系エマルション樹脂、フッ素系エマルション樹脂が挙げられる。特に水系バインダーがポリアクリル酸（ＰＡＡ）であることが好ましい。水系バインダーがポリアクリル酸（ＰＡＡ）である場合は、水系バインダー含有水は酸性を示す。そのため、ポリアクリル酸（ＰＡＡ）含有水と、上記導電性粒子の水分散体とを、従来の方法で混合すると、導電性粒子が特に凝集しやすい。従って、水系バインダーがポリアクリル酸（ＰＡＡ）である場合は、上記保護層形成用組成物調製工程を行うことによる導電性粒子の凝集抑制効果が顕著である。 As an aqueous binder, a water-soluble binder and a water-dispersible binder can be used. Examples of the water-soluble binder include polyacrylic acid (PAA) and polyethylene glycol (PEG). Examples of the water dispersible binder include acrylic-styrene emulsion resins and fluorine emulsion resins. In particular, the aqueous binder is preferably polyacrylic acid (PAA). When the aqueous binder is polyacrylic acid (PAA), the aqueous binder-containing water shows acidity. Therefore, when polyacrylic acid (PAA) -containing water and the aqueous dispersion of the conductive particles are mixed by a conventional method, the conductive particles are particularly easily aggregated. Therefore, when the water-based binder is polyacrylic acid (PAA), the effect of suppressing aggregation of conductive particles by performing the protective layer forming composition preparation step is remarkable.
水系バインダー含有水における水系バインダーの含有量は、０．１質量％以上５０．０質量％以下であることが好ましく、０．５質量％以上１０．０質量％以下であることがさらに好ましい。水系バインダーの含有量が０．１質量％より少ないと、保護層形成用組成物を作製した際に固形分率が小さくなりすぎて塗工性が悪くなり、乾燥効率も低下する。また、水系バインダーの含有量が５０．０質量％より多いと、水系バインダー含有水の粘度が非常に高くなり、導電性粒子と混合させる際に混合性が悪くなるおそれがある。 The content of the aqueous binder in the aqueous binder-containing water is preferably 0.1% by mass or more and 50.0% by mass or less, and more preferably 0.5% by mass or more and 10.0% by mass or less. When the content of the aqueous binder is less than 0.1% by mass, the solid content becomes too small when the protective layer forming composition is produced, the coating property is deteriorated, and the drying efficiency is also lowered. Moreover, when there is more content of an aqueous binder than 50.0 mass%, the viscosity of aqueous binder containing water will become very high, and there exists a possibility that a mixing property may worsen when mixing with electroconductive particle.
保護層形成用組成物調製工程は、上記導電性粒子の水分散体を攪拌機で１０００ｒｐｍ以上の回転数で攪拌しながら水系バインダー含有水を添加することによって、保護層形成用組成物を調製する。 In the protective layer-forming composition preparation step, the protective layer-forming composition is prepared by adding water-based binder-containing water while stirring the aqueous dispersion of the conductive particles with a stirrer at a rotation speed of 1000 rpm or more.
攪拌機は、かき混ぜる装置である。攪拌機として、例えば、ホモディスパー、ホモミキサー、ホモジナイザーが挙げられる。攪拌機は、高粘度でも高速攪拌でき、混合性能の高いホモディスパーが好ましい。 The stirrer is a device for stirring. Examples of the stirrer include a homodisper, a homomixer, and a homogenizer. The stirrer is preferably a homodisper that can stir at high speed even with high viscosity and has high mixing performance.
攪拌条件としては、１０００ｒｐｍ以上６０００ｒｐｍ以下の回転数とすることが好ましく、１５００ｒｐｍ以上３０００ｒｐｍ以下の回転数とすることがより好ましい。１０００ｒｐｍより小さい回転数で攪拌を行うと、上記導電性粒子の凝集が起こるおそれがある。また６０００ｒｐｍより大きい回転数で攪拌を行うことは、攪拌機という装置の能力的に難しい。 As stirring conditions, it is preferable to set it as the rotation speed of 1000 rpm or more and 6000 rpm or less, and it is more preferable to set it as 1500 rpm or more and 3000 rpm or less. When stirring is performed at a rotational speed lower than 1000 rpm, the conductive particles may be aggregated. In addition, it is difficult in terms of the ability of a device called a stirrer to stir at a rotational speed greater than 6000 rpm.
また導電性粒子の水分散体と水系バインダー含有水との混合にはその添加順序が重要であり、導電性粒子の水分散体を高速攪拌させながら、導電性粒子の水分散体に水系バインダー含有水を添加することが好ましい。添加順序を逆にして水系バインダー含有水に導電性粒子の水分散体を添加すると導電性粒子が凝集しやすい。 In addition, the order of addition is important for mixing the aqueous dispersion of conductive particles and water containing an aqueous binder, and the aqueous dispersion of conductive particles contains an aqueous binder while stirring the aqueous dispersion of conductive particles at high speed. It is preferable to add water. When the addition order is reversed and the aqueous dispersion of conductive particles is added to water containing the aqueous binder, the conductive particles tend to aggregate.
また導電性粒子の水分散体に対する水系バインダー含有水の添加は、一気に添加するよりは少し時間をかけて添加する方が、混合系の急激なｐＨ変化が抑制でき、導電性粒子の凝集挙動を抑えることができる。例えば、１０ｇ〜４０ｇの導電性粒子の水分散体に６０ｇ〜９０ｇの水系バインダー含有水を５分〜６０分で添加するのが好ましい。 Addition of aqueous binder-containing water to the aqueous dispersion of conductive particles can suppress abrupt pH change of the mixed system by adding a little time rather than adding all at once, and the aggregation behavior of the conductive particles can be suppressed. Can be suppressed. For example, 60 g to 90 g of water-based binder-containing water is preferably added to an aqueous dispersion of 10 g to 40 g of conductive particles in 5 minutes to 60 minutes.
導電性粒子と水系バインダー含有水に含まれる水系バインダーとの配合比は、固形分の質量比で導電性粒子：水系バインダー＝８０：２０〜９９．９：０．１であることが好ましい。保護層における水系バインダーの含有割合は、０．１質量％以上２０質量％以下が好ましい。水系バインダーの含有割合が２０質量％より多いと、導電性粒子の含有割合が少なくなって保護層の導電性が下がるおそれがあり、水系バインダーの含有割合が０．１質量％より小さいと、導電性粒子を集電体本体に結着させるバインダー効果が得られない。 The compounding ratio of the conductive particles and the aqueous binder contained in the aqueous binder-containing water is preferably conductive particles: aqueous binder = 80: 20 to 99.9: 0.1 based on the mass ratio of the solid content. The content of the aqueous binder in the protective layer is preferably 0.1% by mass or more and 20% by mass or less. When the content ratio of the aqueous binder is more than 20% by mass, the content ratio of the conductive particles may decrease, and the conductivity of the protective layer may be lowered. When the content rate of the aqueous binder is less than 0.1% by mass, the conductive The binder effect that binds the conductive particles to the current collector body cannot be obtained.
保護層形成工程では、アルミニウム箔からなる集電体本体に保護層形成用組成物を塗布し、乾燥して集電体本体の表面に保護層を形成する。 In the protective layer forming step, the protective layer-forming composition is applied to the current collector body made of aluminum foil and dried to form a protective layer on the surface of the current collector body.
集電体本体は、アルミニウム箔からなる。 The current collector body is made of aluminum foil.
アルミニウムとしては、純アルミニウム又はアルミニウム合金が挙げられる。純度９９．０％以上のアルミニウムを純アルミニウムと称し、又種々の元素を添加して合金としたものをアルミニウム合金と称す。アルミニウム合金としては、Ａｌ−Ｃｕ系、Ａｌ−Ｍｎ系、Ａｌ−Ｆｅ系、Ａｌ−Ｓｉ系、Ａｌ−Ｍｇ系、ＡＬ−Ｍｇ−Ｓｉ系、Ａｌ−Ｚｎ−Ｍｇ系が挙げられる。またアルミニウム合金としては、例えばＪＩＳ Ａ１０８５、Ａ１Ｎ３０等のＡ１０００系合金（純アルミニウム系)、ＪＩＳ Ａ３００３、Ａ３００４等のＡ３０００系合金（Ａｌ−Ｍｎ系）、ＪＩＳ Ａ８０７９、Ａ８０２１等のＡ８０００系合金（Ａｌ−Ｆｅ系）が挙げられる。 Examples of aluminum include pure aluminum and aluminum alloys. Aluminum having a purity of 99.0% or more is referred to as pure aluminum, and an alloy obtained by adding various elements is referred to as an aluminum alloy. Examples of the aluminum alloy include Al—Cu, Al—Mn, Al—Fe, Al—Si, Al—Mg, AL—Mg—Si, and Al—Zn—Mg. Examples of the aluminum alloy include A1000 series alloys (pure aluminum series) such as JIS A1085 and A1N30, A3000 series alloys (Al-Mn series) such as JIS A3003 and A3004, and A8000 series alloys such as JIS A8079 and A8021 (Al--). Fe-based).
ここで集電体とは、リチウムイオン二次電池の放電又は充電の間、電極に電流を流し続けるための化学的に不活性な電子高伝導体をいう。 Here, the current collector refers to a chemically inert electronic high conductor that keeps a current flowing through an electrode during discharge or charging of a lithium ion secondary battery.
アルミニウム箔の厚みは、１０μｍ〜１００μｍであることが好ましく、１５μｍ〜２５μｍであることがさらに好ましい。この範囲の厚みを有するアルミニウム箔は集電体用に好適に用いられる。 The thickness of the aluminum foil is preferably 10 μm to 100 μm, and more preferably 15 μm to 25 μm. An aluminum foil having a thickness in this range is suitably used for a current collector.
保護層形成用組成物の塗布には、ロールコート法、ディップコート法、ドクターブレード法、スプレーコート法、カーテンコート法などの従来から公知の方法を用いればよい。 For the application of the protective layer forming composition, a conventionally known method such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method may be used.
乾燥は、保護層形成用組成物から水を蒸発させることができる温度及び時間で行えばよい。例えば、保護層形成用組成物を塗布したアルミニウム箔を４０℃〜１２０℃で３分〜１５分乾燥させることによってアルミニウム箔上に保護層を形成できる。 Drying may be performed at a temperature and a time at which water can be evaporated from the protective layer forming composition. For example, a protective layer can be formed on an aluminum foil by drying the aluminum foil coated with the composition for forming a protective layer at 40 ° C. to 120 ° C. for 3 minutes to 15 minutes.
保護層形成工程の前に、アルミニウム箔を８０℃〜１６０℃で１時間以上保持する熱処理を行って熱処理済アルミニウム箔を得るアルミニウム箔の熱処理工程をさらに実施することが好ましい。そして保護層形成工程のアルミニウム箔は熱処理済みアルミニウム箔であることが好ましい。 Prior to the protective layer forming step, it is preferable to further perform a heat treatment step of the aluminum foil to obtain a heat-treated aluminum foil by performing a heat treatment for holding the aluminum foil at 80 ° C. to 160 ° C. for 1 hour or more. The aluminum foil in the protective layer forming step is preferably a heat-treated aluminum foil.
アルミニウム箔を８０℃〜１６０℃で１時間以上保持する熱処理により、アルミニウム箔を軟化させることなく脱脂してアルミニウム箔表面のぬれ性を向上させることができる。 By the heat treatment in which the aluminum foil is held at 80 ° C. to 160 ° C. for 1 hour or longer, the aluminum foil can be degreased without softening and the wettability of the aluminum foil surface can be improved.
処理温度が８０℃未満では長時間をかけても脱脂効果が少なく、１６０℃を超えると箔が軟化し、アルミニウム箔の強度が低下する。１時間未満の処理時間では脱脂効果に乏しい。８０℃〜１６０℃という温度で熱処理を行うので処理時間が長時間となっても強度が低下するおそれはない。ただし１００時間を超える長時間熱処理を行っても脱脂効果が飽和してそれ以上の効果が得られない。このため処理時間は１００時間以下が好ましい。処理温度が高いほど短時間で脱脂される。またアルミニウム箔を構成する材料によって、熱の影響が異なる。このため処理温度及びアルミニウム箔の構成材料に応じて処理時間を設定すればよい。例えば、純アルミニウムよりなるアルミニウム箔を１３０℃〜２５０℃で１時間〜２４時間熱処理することが好ましく、１５０℃〜２００℃で３時間〜２０時間熱処理することがさらに好ましい。 If the treatment temperature is less than 80 ° C., the degreasing effect is small even if it takes a long time, and if it exceeds 160 ° C., the foil is softened and the strength of the aluminum foil is lowered. When the treatment time is less than 1 hour, the degreasing effect is poor. Since the heat treatment is performed at a temperature of 80 ° C. to 160 ° C., there is no possibility that the strength is lowered even if the treatment time is long. However, the degreasing effect is saturated even if heat treatment is performed for more than 100 hours, and no further effect is obtained. Therefore, the treatment time is preferably 100 hours or less. The higher the processing temperature, the shorter the degreasing time. The influence of heat differs depending on the material constituting the aluminum foil. For this reason, what is necessary is just to set processing time according to processing temperature and the constituent material of aluminum foil. For example, an aluminum foil made of pure aluminum is preferably heat-treated at 130 ° C. to 250 ° C. for 1 hour to 24 hours, more preferably 150 ° C. to 200 ° C. for 3 hours to 20 hours.
熱処理を行うときのアルミニウム箔の形態は、ロール状の形態でも積層状の形態でもよい。 The form of the aluminum foil when the heat treatment is performed may be a roll form or a laminated form.
保護層は、その厚みが１００ｎｍ〜１０００ｎｍとなるように形成されることが好ましい。厚みが１０００ｎｍより厚い保護層を有する集電体を正極に用いるリチウムイオン二次電池は、正極における正極活物質の含有割合が低下して、リチウムイオン二次電池の充放電容量が低下するおそれがある。保護層の厚みが１００ｎｍより薄いと、保護層による集電体の保護効果が得られにくい。 The protective layer is preferably formed so as to have a thickness of 100 nm to 1000 nm. In a lithium ion secondary battery using a current collector having a protective layer with a thickness greater than 1000 nm as a positive electrode, the content ratio of the positive electrode active material in the positive electrode may decrease, and the charge / discharge capacity of the lithium ion secondary battery may decrease. is there. When the thickness of the protective layer is less than 100 nm, it is difficult to obtain the current collector protecting effect by the protective layer.
本発明の集電体本体への保護層形成方法によれば、導電性粒子の凝集が抑制され、アルミニウム箔へ均一な保護層を形成できる。 According to the method for forming a protective layer on the current collector body of the present invention, aggregation of conductive particles is suppressed, and a uniform protective layer can be formed on the aluminum foil.
＜リチウムイオン二次電池用集電体＞
本発明のリチウムイオン二次電池用集電体は、アルミニウム箔と、上記アルミニウム箔への保護層形成方法を経て形成された保護層と、からなることを特徴とする。
<Current collector for lithium ion secondary battery>
The current collector for a lithium ion secondary battery of the present invention is characterized by comprising an aluminum foil and a protective layer formed through the method for forming a protective layer on the aluminum foil.
アルミニウム箔の説明は上記アルミニウム箔への保護層形成方法に記載したことと同様である。 The description of the aluminum foil is the same as described in the method for forming a protective layer on the aluminum foil.
上記保護層は、上記導電性粒子と水系バインダーとからなる。保護層における水系バインダーの含有割合は、０．１質量％以上２０質量％以下が好ましい。水系バインダーの含有割合が２０質量％より多いと、保護層の導電性が下がるおそれがある。水系バインダーの含有割合が０．１質量％より少ないと、導電性粒子を集電体本体に結着させるバインダー効果が得られない。導電性粒子及び水系バインダーについての説明は上記したアルミニウム箔への保護層形成方法に記載したことと同様である。 The protective layer is composed of the conductive particles and an aqueous binder. The content of the aqueous binder in the protective layer is preferably 0.1% by mass or more and 20% by mass or less. If the content of the aqueous binder is more than 20% by mass, the conductivity of the protective layer may be lowered. When the content of the aqueous binder is less than 0.1% by mass, the binder effect that binds the conductive particles to the current collector body cannot be obtained. The explanation about the conductive particles and the aqueous binder is the same as that described in the method for forming the protective layer on the aluminum foil.
凝集しにくい状態の保護層形成用組成物を使用して保護層を形成しているので、形成された保護層において、導電性粒子は、より均一に分散されている。従って上記方法で形成された保護層は、導電性粒子が均一に分散された保護層となり、アルミニウム箔を電解液から均一に保護することができる。 Since the protective layer is formed using the protective layer-forming composition that is not easily aggregated, the conductive particles are more uniformly dispersed in the formed protective layer. Therefore, the protective layer formed by the above method becomes a protective layer in which conductive particles are uniformly dispersed, and the aluminum foil can be uniformly protected from the electrolytic solution.
集電体本体の表面に保護層が配置されているため、Ａｌ２Ｏ３、ＡｌＦ３等の不動態膜が形成されにくい。そのため、この保護層によって、不動態膜からなる高抵抗層が集電体本体の表面に形成されることを抑制でき、かつ集電体本体を電解液から保護することができる。 Since the protective layer is disposed on the surface of the current collector body, it is difficult to form a passive film such as Al 2 O 3 or AlF 3 . Therefore, this protective layer can suppress the formation of a high resistance layer made of a passive film on the surface of the current collector body, and can protect the current collector body from the electrolytic solution.
保護層の厚みは１００ｎｍ以上１０００ｎｍ以下であることが好ましい。さらに保護層の厚みは１５０ｎｍ以上８００ｎｍ以下であることがより好ましい。１０００ｎｍより厚い保護層を有する集電体を正極に用いるリチウムイオン二次電池は、正極における正極活物質の含有割合の低下により、リチウムイオン二次電池の充放電容量が低下するおそれがある。保護層の厚みが１００ｎｍより薄いと、保護層による集電体の保護効果が得られにくい。 The thickness of the protective layer is preferably 100 nm or more and 1000 nm or less. Furthermore, the thickness of the protective layer is more preferably 150 nm or more and 800 nm or less. In a lithium ion secondary battery using a current collector having a protective layer thicker than 1000 nm as a positive electrode, the charge / discharge capacity of the lithium ion secondary battery may decrease due to a decrease in the content of the positive electrode active material in the positive electrode. When the thickness of the protective layer is less than 100 nm, it is difficult to obtain the current collector protecting effect by the protective layer.
図１に本実施形態のリチウムイオン二次電池用集電体を説明する模式図を示す。図１において、集電体本体１の上に保護層２が配置されている。リチウムイオン二次電池用集電体３は、集電体本体１と保護層２とからなる。 FIG. 1 is a schematic diagram illustrating a current collector for a lithium ion secondary battery according to this embodiment. In FIG. 1, a protective layer 2 is disposed on a current collector body 1. A current collector 3 for a lithium ion secondary battery includes a current collector body 1 and a protective layer 2.
＜リチウムイオン二次電池用正極＞
本発明のリチウムイオン二次電池用正極は、上記リチウムイオン二次電池用集電体を有することを特徴とする。
<Positive electrode for lithium ion secondary battery>
The positive electrode for lithium ion secondary batteries of this invention has the said collector for lithium ion secondary batteries, It is characterized by the above-mentioned.
正極は、上記リチウムイオン二次電池用集電体と、リチウムイオン二次電池用集電体に配置された正極活物質層とを有する。 A positive electrode has the said collector for lithium ion secondary batteries, and the positive electrode active material layer arrange | positioned at the collector for lithium ion secondary batteries.
正極活物質層は、正極活物質と結着剤とを含む。正極活物質層は必要に応じて導電助剤をさらに含んでも良い。 The positive electrode active material layer includes a positive electrode active material and a binder. The positive electrode active material layer may further contain a conductive additive as necessary.
正極活物質としては、リチウム含有化合物あるいは他の金属化合物よりなるものを用いることができる。リチウム含有化合物としては、例えば、層状構造を有するリチウムコバルト複合酸化物、層状構造を有するリチウムニッケル複合酸化物、スピネル構造を有するリチウムマンガン複合酸化物、一般式：ＬｉａＣｏｐＮｉｑＭｎｒＤｓＯｘ(Ｄは、Ａｌ、Ｍｇ、Ｔｉ、Ｓｎ、Ｚｎ、Ｗ、Ｚｒ、Ｍｏ、Ｆｅ及びＮａから選択される少なくとも一種、ｐ＋ｑ＋ｒ＋ｓ＝１、０＜ｐ＜１、０≦ｑ＜１、０≦ｒ＜１、０≦ｓ＜１、０．８≦ａ＜２．０、−０．２≦ｘ−（ａ＋ｐ＋ｑ＋ｒ＋ｓ）≦０．２)で表される層状構造を有するリチウムコバルト含有複合金属酸化物、一般式：ＬｉＭＰＯ４で示されるオリビン型リチウムリン酸複合酸化物（ＭはＭｎ、Ｆｅ、Ｃｏ及びＮｉのうちの少なくとも一種）、一般式：Ｌｉ２ＭＰＯ４Ｆで示されるフッ化オリビン型リチウムリン酸複合酸化物（ＭはＭｎ、Ｆｅ、Ｃｏ及びＮｉのうちの少なくとも一種）、一般式：Ｌｉ２ＭＳｉＯ４で示されるケイ酸塩系型リチウム複合酸化物（ＭはＭｎ、Ｆｅ、Ｃｏ及びＮｉのうちの少なくとも一種）を用いることができる。また他の金属化合物としては、例えば、酸化チタン、酸化バナジウム若しくは二酸化マンガンなどの酸化物、又は硫化チタン若しくは硫化モリブデンなどの硫化物が挙げられる。 As the positive electrode active material, a lithium-containing compound or another metal compound can be used. Examples of the lithium-containing compound, for example, lithium-cobalt composite oxide having a layered structure, the lithium nickel composite oxide having a layered structure, the lithium manganese composite oxide having a spinel structure represented by the general formula: Li a Co p Ni q Mn r D s O x (D is at least one selected from Al, Mg, Ti, Sn, Zn, W, Zr, Mo, Fe and Na, p + q + r + s = 1, 0 <p <1, 0 ≦ q <1, 0 ≦ r <1, 0 ≦ s <1, 0.8 ≦ a <2.0, −0.2 ≦ x− (a + p + q + r + s) ≦ 0.2) Olivine-type lithium phosphate complex oxide represented by LiMPO 4 (M is at least one of Mn, Fe, Co and Ni), represented by general formula: Li 2 MPO 4 F Fluorine olivine type lithium phosphate complex oxide (M is at least one of Mn, Fe, Co and Ni), silicate type lithium complex oxide represented by general formula: Li 2 MSiO 4 (M is Mn , Fe, Co, and Ni). Examples of other metal compounds include oxides such as titanium oxide, vanadium oxide, and manganese dioxide, and sulfides such as titanium sulfide and molybdenum sulfide.
正極活物質は、化学式：ＬｉＭＯ２（ＭはＮｉ、Ｃｏ及びＭｎから選択される少なくとも１つである）で表されるリチウム含有酸化物よりなることが好ましく、さらに上記した層状構造を有するリチウムコバルト含有複合金属酸化物よりなることが好ましい。 The positive electrode active material is preferably composed of a lithium-containing oxide represented by the chemical formula: LiMO 2 (M is at least one selected from Ni, Co, and Mn), and lithium cobalt having the layered structure described above. The composite metal oxide is preferably included.
リチウム含有酸化物としては、例えば、ＬｉＣｏ１／３Ｎｉ１／３Ｍｎ１／３Ｏ２、ＬｉＮｉ０．６Ｃｏ０．２Ｍｎ０．２Ｏ２、ＬｉＮｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２、ＬｉＣｏＯ２、ＬｉＮｉ０．８Ｃｏ０．２Ｏ２、ＬｉＣｏＭｎＯ２を用いることができる。中でもＬｉＣｏ１／３Ｎｉ１／３Ｍｎ１／３Ｏ２、ＬｉＮｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２は、熱安定性の点で好ましい。 Examples of the lithium-containing oxide include LiCo 1/3 Ni 1/3 Mn 1/3 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.5 Co 0.2 Mn 0. 3 O 2 , LiCoO 2 , LiNi 0.8 Co 0.2 O 2 , LiCoMnO 2 can be used. Among these, LiCo 1/3 Ni 1/3 Mn 1/3 O 2 and LiNi 0.5 Co 0.2 Mn 0.3 O 2 are preferable in terms of thermal stability.
正極活物質はその平均粒径Ｄ５０が１μｍ〜２０μｍである粉末形状であることが好ましい。正極活物質の平均粒径Ｄ５０が１μｍより小さいと正極活物質の比表面積が大きくなり正極活物質と非水電解液との反応面積が増える。正極活物質の平均粒径Ｄ５０が２０μｍより大きいとリチウムイオン二次電池の抵抗が大きくなり、リチウムイオン二次電池の出力特性が下がるおそれがある。平均粒径Ｄ５０は、粒度分布測定法によって計測できる。平均粒径Ｄ５０とはレーザー回析法による粒度分布測定における体積分布の積算値が５０％に相当する粒子径のことである。つまり、平均粒径Ｄ５０とは、体積基準で測定したメディアン径を意味する。 The positive electrode active material preferably has an average particle diameter D 50 is a powder shape is 1 m to 20 m. The average particle diameter D 50 of the positive electrode active material increases the reaction area of 1μm smaller than the specific surface area of the cathode active material increases the positive electrode active material and the nonaqueous electrolyte. The average particle diameter D 50 of the positive electrode active material becomes large 20μm greater than the resistance of the lithium ion secondary battery, there is a possibility that the output characteristics of the lithium ion secondary battery decreases. The average particle diameter D 50 can be measured by particle size distribution measurement method. The average particle diameter D 50 is that the particle size cumulative value of the volume distribution in the particle size distribution measurement by laser diffraction method is equivalent to 50%. That is, the average particle diameter D 50 means the median size measured by volume.
結着剤は、上記正極活物質及び導電助剤を集電体に繋ぎ止める役割を果たす。結着剤として、例えば、ポリフッ化ビニリデン、ポリテトラフルオロエチレンおよびフッ素ゴム等の含フッ素樹脂、ポリプロピレン、ポリエチレンおよびポリ酢酸ビニル系樹脂等の熱可塑性樹脂、ポリイミドおよびポリアミドイミド等のイミド系樹脂、アルコキシシリル基含有樹脂、並びにスチレンブタジエンゴム（ＳＢＲ）等のゴムを用いることができる。 The binder plays a role of connecting the positive electrode active material and the conductive additive to the current collector. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene and fluororubber, thermoplastic resins such as polypropylene, polyethylene and polyvinyl acetate resins, imide resins such as polyimide and polyamideimide, alkoxy Silyl group-containing resins and rubbers such as styrene butadiene rubber (SBR) can be used.
導電助剤は、必要に応じて電極の導電性を高めるために添加される。導電助剤として、炭素質微粒子であるカーボンブラック、黒鉛、アセチレンブラック（ＡＢ）、ケッチェンブラック（登録商標）（ＫＢ）、気相法炭素繊維（ＶＧＣＦ）等を単独で又は二種以上組み合わせて使用することができる。導電助剤の使用量については、特に限定的ではないが、例えば、正極に含有される活物質１００質量部に対して、１質量部〜３０質量部程度とすることができる。 A conductive support agent is added in order to improve the electroconductivity of an electrode as needed. Carbon black, graphite, acetylene black (AB), ketjen black (registered trademark) (KB), vapor grown carbon fiber (VGCF), etc., which are carbonaceous fine particles, are used alone or in combination of two or more as conductive aids. Can be used. The amount of the conductive auxiliary agent used is not particularly limited, but can be, for example, about 1 part by mass to 30 parts by mass with respect to 100 parts by mass of the active material contained in the positive electrode.
上記集電体の表面に正極活物質層を配置するには、ロールコート法、ディップコート法、ドクターブレード法、スプレーコート法、カーテンコート法などの従来から公知の方法を用いて、集電体の表面に正極活物質を直接塗布すればよい。具体的には、正極活物質、結着剤及び必要に応じて導電助剤を含む正極活物質層形成用組成物を調製し、この組成物に適当な溶媒を加えてスラリーとする。結着剤は、あらかじめ結着剤を溶媒に溶解させた溶液又は分散させた懸濁液としてから用いてもよい。上記溶媒としては、Ｎ−メチル−２−ピロリドン（ＮＭＰ）、メタノール、メチルイソブチルケトン（ＭＩＢＫ）を例示できる。上記スラリーを集電体の表面に塗布後、乾燥する。乾燥は、常圧条件で行ってもよいし、真空乾燥機を用いた減圧条件下で行ってもよい。乾燥温度は適宜設定すればよく、上記溶媒の沸点以上の温度が好ましい。乾燥時間は塗布量及び乾燥温度に応じ適宜設定すればよい。正極活物質層の密度を高めるべく、乾燥により正極活物質層を形成させた後の集電体に対し、圧縮工程を加えてもよい。 In order to dispose the positive electrode active material layer on the surface of the current collector, a current collector is used by a conventionally known method such as a roll coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method. What is necessary is just to apply | coat a positive electrode active material directly on the surface of this. Specifically, a positive electrode active material layer-forming composition containing a positive electrode active material, a binder and, if necessary, a conductive additive is prepared, and an appropriate solvent is added to the composition to form a slurry. The binder may be used as a solution in which the binder is dissolved in a solvent or a dispersed suspension in advance. Examples of the solvent include N-methyl-2-pyrrolidone (NMP), methanol, and methyl isobutyl ketone (MIBK). The slurry is applied to the surface of the current collector and then dried. Drying may be performed under normal pressure conditions, or under reduced pressure conditions using a vacuum dryer. What is necessary is just to set drying temperature suitably, and the temperature beyond the boiling point of the said solvent is preferable. What is necessary is just to set drying time suitably according to an application quantity and drying temperature. In order to increase the density of the positive electrode active material layer, a compression step may be added to the current collector after the positive electrode active material layer is formed by drying.
＜リチウムイオン二次電池＞
本発明のリチウムイオン二次電池は、上記リチウムイオン二次電池用正極を有することを特徴とする。
<Lithium ion secondary battery>
The lithium ion secondary battery of this invention has the said positive electrode for lithium ion secondary batteries, It is characterized by the above-mentioned.
本発明のリチウムイオン二次電池は、電池構成要素として、正極、負極、セパレータ、電解液を有する。正極は上記リチウムイオン二次電池用正極である。 The lithium ion secondary battery of this invention has a positive electrode, a negative electrode, a separator, and electrolyte solution as a battery component. The positive electrode is the positive electrode for a lithium ion secondary battery.
負極は、集電体と、集電体の表面に結着させた負極活物質層を有する。負極活物質層は、負極活物質、結着剤を含み、必要に応じて導電助剤を含む。集電体、結着剤、導電助剤は正極で説明したものと同様である。 The negative electrode has a current collector and a negative electrode active material layer bound to the surface of the current collector. A negative electrode active material layer contains a negative electrode active material and a binder, and contains a conductive support agent as needed. The current collector, binder and conductive additive are the same as those described for the positive electrode.
負極活物質としては、リチウムを吸蔵、放出可能な炭素系材料、リチウムと合金化可能な元素、リチウムと合金化可能な元素を有する化合物、あるいは高分子材料などを用いることができる。 As the negative electrode active material, a carbon-based material that can occlude and release lithium, an element that can be alloyed with lithium, a compound that includes an element that can be alloyed with lithium, a polymer material, or the like can be used.
炭素系材料としては、例えば、難黒鉛化性炭素、人造黒鉛、天然黒鉛、コークス類、グラファイト類、ガラス状炭素類、有機高分子化合物焼成体、炭素繊維、活性炭あるいはカーボンブラック類が挙げられる。ここで、有機高分子化合物焼成体とは、フェノール類やフラン類などの高分子材料を適当な温度で焼成して炭素化したものをいう。 Examples of the carbon-based material include non-graphitizable carbon, artificial graphite, natural graphite, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers, activated carbon, and carbon blacks. Here, the organic polymer compound fired body refers to a material obtained by firing and carbonizing a polymer material such as phenols and furans at an appropriate temperature.
リチウムと合金化可能な元素は、Ｎａ、Ｋ、Ｒｂ、Ｃｓ、Ｆｒ、Ｂｅ、Ｍｇ、Ｃａ、Ｓｒ、Ｂａ、Ｒａ、Ｔｉ、Ａｇ、Ｚｎ、Ｃｄ、Ａｌ、Ｇａ、Ｉｎ、Ｓｉ、Ｇｅ、Ｓｎ、Ｐｂ、Ｓｂ、Ｂｉである。中でも、リチウムと合金化可能な元素は、珪素（Ｓｉ）又は錫（Ｓｎ）であるとよい。 Elements that can be alloyed with lithium are Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si, Ge, Sn. , Pb, Sb, Bi. Among them, the element that can be alloyed with lithium is preferably silicon (Si) or tin (Sn).
リチウムと合金化可能な元素を有する化合物としては、例えば、ＺｎＬｉＡｌ、ＡｌＳｂ、ＳｉＢ４、ＳｉＢ６、Ｍｇ２Ｓｉ、Ｍｇ２Ｓｎ、Ｎｉ２Ｓｉ、ＴｉＳｉ２、ＭｏＳｉ２、ＣｏＳｉ２、ＮｉＳｉ２、ＣａＳｉ２、ＣｒＳｉ２、Ｃｕ５Ｓｉ、ＦｅＳｉ２、ＭｎＳｉ２、ＮｂＳｉ２、ＴａＳｉ２、ＶＳｉ２、ＷＳｉ２、ＺｎＳｉ２、ＳｉＣ、Ｓｉ３Ｎ４、Ｓｉ２Ｎ２Ｏ、ＳｉＯｖ（０＜ｖ≦２）、ＳｎＯｗ（０＜ｗ≦２）、ＳｎＳｉＯ３、ＬｉＳｉＯあるいはＬｉＳｎＯが使用できる。リチウムと合金化可能な元素を有する化合物としては、珪素化合物又は錫化合物が好ましい。珪素化合物としては、ＳｉＯｘ（０．５≦ｘ≦１．６）が好ましい。錫化合物としては、スズ合金（Ｃｕ−Ｓｎ合金、Ｃｏ−Ｓｎ合金等）を例示できる。 Examples of the compound having an element that can be alloyed with lithium include ZnLiAl, AlSb, SiB 4 , SiB 6 , Mg 2 Si, Mg 2 Sn, Ni 2 Si, TiSi 2 , MoSi 2 , CoSi 2 , NiSi 2 , and CaSi. 2, CrSi 2, Cu 5 Si , FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO v (0 <v ≦ 2), SnO w (0 <w ≦ 2), SnSiO 3 , LiSiO or LiSnO can be used. As the compound having an element that can be alloyed with lithium, a silicon compound or a tin compound is preferable. As the silicon compound, SiO x (0.5 ≦ x ≦ 1.6) is preferable. Examples of the tin compound include tin alloys (Cu—Sn alloy, Co—Sn alloy, etc.).
高分子材料としては、ポリアセチレン、ポリピロールを例示できる。 Examples of the polymer material include polyacetylene and polypyrrole.
セパレータは正極と負極とを隔離し、両極の接触による電流の短絡を防止しつつ、リチウムイオンを通過させるものである。セパレータは、例えばポリテトラフルオロエチレン、ポリプロピレン、あるいはポリエチレンなどの合成樹脂製の多孔質膜、又はセラミックス製の多孔質膜が使用できる。 The separator separates the positive electrode and the negative electrode and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. As the separator, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramics can be used.
電解液は、溶媒とこの溶媒に溶解された電解質とを含んでいる。 The electrolytic solution includes a solvent and an electrolyte dissolved in the solvent.
溶媒として、例えば、環状エステル類、鎖状エステル類、エーテル類が使用できる。環状エステル類として、例えば、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ガンマブチロラクトン、ビニレンカーボネート、２−メチル−ガンマブチロラクトン、アセチル−ガンマブチロラクトン、ガンマバレロラクトンが使用できる。鎖状エステル類として、例えば、ジメチルカーボネート、ジエチルカーボネート、ジブチルカーボネート、ジプロピルカーボネート、メチルエチルカーボネート、プロピオン酸アルキルエステル、マロン酸ジアルキルエステル、酢酸アルキルエステルが使用できる。エーテル類として、例えば、テトラヒドロフラン、２−メチルテトラヒドロフラン、１，４−ジオキサン、１，２−ジメトキシエタン、１，２−ジエトキシエタン、１，２−ジブトキシエタンが使用できる。 As the solvent, for example, cyclic esters, chain esters, and ethers can be used. Examples of cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma butyrolactone, and gamma valerolactone. Examples of the chain esters include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers that can be used include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane.
また上記電解液に溶解させる電解質として、例えば、ＬｉＣｌＯ４、ＬｉＡｓＦ６、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣＦ３ＳＯ３、ＬｉＮ（ＣＦ３ＳＯ２）２等のリチウム塩を使用することができる。 Moreover, as an electrolyte dissolved in the electrolytic solution, for example, a lithium salt such as LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 can be used.
電解液として、例えば、エチレンカーボネート、ジメチルカーボネート、プロピレンカーボネート、ジメチルカーボネートなどの溶媒にＬｉＣｌＯ４、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣＦ３ＳＯ３などのリチウム塩を０．５ｍｏｌ／ｌから１．７ｍｏｌ／ｌ程度の濃度で溶解させた溶液を使用することができる。 As the electrolytic solution, for example, a lithium salt such as LiClO 4 , LiPF 6 , LiBF 4 , LiCF 3 SO 3 in a solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, dimethyl carbonate, or the like is from 0.5 mol / l to 1.7 mol / l. A solution dissolved at a certain concentration can be used.
上記リチウムイオン二次電池は車両に搭載することができる。上記リチウムイオン二次電池を搭載した車両は、寿命、出力の面で高性能となる。 The lithium ion secondary battery can be mounted on a vehicle. A vehicle equipped with the lithium ion secondary battery has high performance in terms of life and output.
車両としては、電池による電気エネルギーを動力源の全部又は一部に使用する車両であればよく、例えば、電気自動車、ハイブリッド自動車、プラグインハイブリッド自動車、ハイブリッド鉄道車両、電動フォークリフト、電気車椅子、電動アシスト自転車、電動二輪車が挙げられる。 The vehicle may be a vehicle that uses electric energy from a battery as a whole or a part of a power source. For example, an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, a hybrid railway vehicle, an electric forklift, an electric wheelchair, an electric assist Bicycles and electric motorcycles are examples.
以上、本発明のアルミニウム箔への保護層形成方法、リチウムイオン二次電池用集電体リチウムイオン二次電池用正極及びリチウムイオン二次電池の実施形態を説明したが、本発明は、上記実施形態に限定されるものではない。本発明の要旨を逸脱しない範囲において、当業者が行い得る変更、改良等を施した種々の形態にて実施することができる。 As mentioned above, although the protective layer formation method to the aluminum foil of this invention, the collector for lithium ion secondary batteries, the positive electrode for lithium ion secondary batteries, and embodiment of a lithium ion secondary battery were demonstrated, this invention is the said implementation. The form is not limited. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.
以下、実施例を挙げて本発明を更に詳しく説明する。 Hereinafter, the present invention will be described in more detail with reference to examples.
＜保護層形成用組成物＞
導電性粒子の水分散体として以下の３種類を準備した。
<Composition for forming protective layer>
The following three types were prepared as aqueous dispersions of conductive particles.
アンチモンドープ酸化スズは以下ＡＴＯと称す。 Antimony-doped tin oxide is hereinafter referred to as ATO.
ＡＴＯ水系分散体（１）として、三菱マテリアル電子化成株式会社製ＴＤＬ−１（一次粒子径が５０ｎｍ以下の球状粒子、固形分１７．５質量％）を準備した。ＡＴＯ水系分散体（２）として、石原産業株式会社製ＳＮ−１００Ｄ（一次粒子径が５０ｎｍ以下の球状粒子、固形分２９．９質量％）を準備した。ＡＴＯ水系分散体（３）として石原産業株式会社製ＦＳ−１０Ｄ（長軸０．２μｍ〜２μｍ、短軸０．０１μｍ〜０．０２μｍ、アスペクト比（長軸／短軸）が２０〜３０の針状粒子、固形分２０．６質量％）を準備した。 As an ATO aqueous dispersion (1), TDL-1 (spherical particles having a primary particle diameter of 50 nm or less, solid content of 17.5% by mass) manufactured by Mitsubishi Materials Electronics Chemical Co., Ltd. was prepared. As an ATO aqueous dispersion (2), Ishihara Sangyo Co., Ltd. SN-100D (spherical particles having a primary particle diameter of 50 nm or less, solid content of 29.9% by mass) was prepared. FS-10D manufactured by Ishihara Sangyo Co., Ltd. (major axis 0.2 μm to 2 μm, minor axis 0.01 μm to 0.02 μm, aspect ratio (major axis / minor axis) 20 to 30) as ATO aqueous dispersion (3) Shaped particles, solid content 20.6% by mass).
水系バインダーとして、以下の２種類を準備した。水系バインダー（１）として、和光純薬工業株式会社製ポリアクリル酸（ＰＡＡ）（平均分子量５０００）を準備した。水系バインダー（２）として、ＢＡＳＦジャパン株式会社製ジョンクリルＰＤＸ７３４１（アクリルースチレン系エマルション）を準備した。 The following two types were prepared as aqueous binders. As an aqueous binder (1), Wako Pure Chemical Industries, Ltd. polyacrylic acid (PAA) (average molecular weight 5000) was prepared. As an aqueous binder (2), BASF Japan Co., Ltd. Jonkrill PDX7341 (acryl-styrene emulsion) was prepared.
＜集電体の形成＞
（実施例１）
ＡＴＯ分散体（１）５００質量部と蒸留水１４１０質量部をプラスチック容器に秤量し、高速攪拌機（プライミクス株式会社製ＴＫロボミックス）で攪拌（１４００ｒｐｍ）させながら、前もって調製した水系バインダー（１）１０％水溶液１００質量部を５分間かけて添加した。更に、添加後１５分間、１４００ｒｐｍで攪拌し実施例１の保護層形成用組成物（ＡＴＯ粒子／水系バインダー＝８９．７／１０．３）を得た。実施例１の保護層形成用組成物の分散粒径Ｄ５０は１０５ｎｍで、経時安定性（２５℃、１週間）も良好であった。
<Formation of current collector>
Example 1
500 parts by weight of ATO dispersion (1) and 1410 parts by weight of distilled water were weighed in a plastic container, and a water-based binder (1) 10 prepared in advance while stirring (1400 rpm) with a high-speed stirrer (TK Robotics manufactured by PRIMIX Corporation). 100 parts by mass of a 5% aqueous solution was added over 5 minutes. Furthermore, it stirred at 1400 rpm for 15 minutes after addition, and obtained the composition for protective layer formation of Example 1 (ATO particle / water-based binder = 89.7 / 10.3). The dispersion particle diameter D 50 of the protective layer-forming composition of Example 1 at 105 nm, stability over time (25 ° C., 1 week) was also good.
分散粒径Ｄ５０（キュムラント平均粒子径）は株式会社堀場製作所製ナノ粒子解析装置ＳＺ−１００で測定した。経時安定性は、保護層形成用組成物を２５℃で１週間保持し、１週間保持後に再度分散粒径Ｄ５０を測定し、保存前の分散粒径Ｄ５０に比べて増大率が３０％以内の場合を経時安定性が良好であると判定した。 The dispersed particle size D 50 (cumulant average particle size) was measured with a nanoparticle analyzer SZ-100 manufactured by Horiba, Ltd. The stability over time was maintained by holding the composition for forming a protective layer at 25 ° C. for 1 week, measuring the dispersed particle size D 50 again after holding for 1 week, and the increase rate was 30% compared to the dispersed particle size D 50 before storage. In the case of within, it was determined that the stability over time was good.
厚み２０μｍのアルミニウム箔（日本製箔株式会社製）を１２０℃で加熱し脱脂処理を行った熱処理済アルミニウム箔を集電体本体として準備した。 A heat-treated aluminum foil obtained by heating a 20 μm-thick aluminum foil (manufactured by Nippon Foil Co., Ltd.) at 120 ° C. and performing a degreasing treatment was prepared as a current collector body.
実施例１の保護層形成用組成物を上記熱処理済アルミニウム箔にマイクログラビアコーターを用いて連続塗工した。実施例１の保護層形成用組成物を塗布後のアルミニウム箔を１２０℃で５分間乾燥した。これにより保護層が形成された実施例１の集電体を形成した。実施例１の集電体において保護層の厚みは１００ｎｍであった。 The protective layer forming composition of Example 1 was continuously applied to the heat-treated aluminum foil using a micro gravure coater. The aluminum foil after the application of the protective layer forming composition of Example 1 was dried at 120 ° C. for 5 minutes. Thus, the current collector of Example 1 in which the protective layer was formed was formed. In the current collector of Example 1, the thickness of the protective layer was 100 nm.
図２に実施例１の集電体の表面を走査型電子顕微鏡（ＳＥＭ）の観察結果を示す。図２にみられるように、実施例１の集電体の表面にある保護層において導電性粒子が均一に分散されていることが観察された。また実施例１の集電体の表面を光学顕微鏡で観察したところ、干渉縞が観察されなかった。このことから実施例１の集電体の表面は表面平滑性が高く、表面の高低差が１００ｎｍ未満であることがわかった。 FIG. 2 shows an observation result of the surface of the current collector of Example 1 with a scanning electron microscope (SEM). As seen in FIG. 2, it was observed that the conductive particles were uniformly dispersed in the protective layer on the surface of the current collector of Example 1. Moreover, when the surface of the electrical power collector of Example 1 was observed with the optical microscope, the interference fringe was not observed. From this, it was found that the surface of the current collector of Example 1 had high surface smoothness and the surface height difference was less than 100 nm.
（実施例２）
ＡＴＯ分散体（２）２９３質量部と蒸留水１８４９質量部をプラスチック容器に秤量し、高速攪拌機（プライミクス株式会社製ＴＫロボミックス）で攪拌（１４００ｒｐｍ）させながら、前もって調製した水系バインダー（１）１０％水溶液１００質量部を５分間かけて添加した。更に、添加後１５分間、１４００ｒｐｍで攪拌し、実施例２の保護層形成用組成物（ＡＴＯ粒子／水系バインダー＝８９．７／１０．３）を得た。実施例２の保護層形成用組成物の分散粒径Ｄ５０は１４７ｎｍで、経時安定性（２５℃、１週間）も良好であった。
(Example 2)
293 parts by weight of ATO dispersion (2) and 1849 parts by weight of distilled water were weighed in a plastic container and stirred in advance (1400 rpm) with a high-speed stirrer (TK Robotics manufactured by Primics Co., Ltd.). 100 parts by mass of a 5% aqueous solution was added over 5 minutes. Furthermore, it stirred at 1400 rpm for 15 minutes after addition, and obtained the composition for protective layer formation of Example 2 (ATO particle / water-based binder = 89.7 / 10.3). The dispersion particle diameter D 50 of the protective layer-forming composition of Example 2 at 147 nm, stability over time (25 ° C., 1 week) was also good.
実施例２の保護層形成用組成物を使用した以外は、実施例１の集電体と同様にして実施例２の集電体を形成した。実施例２の集電体において保護層の厚みは１２０ｎｍであった。 The current collector of Example 2 was formed in the same manner as the current collector of Example 1 except that the composition for forming a protective layer of Example 2 was used. In the current collector of Example 2, the thickness of the protective layer was 120 nm.
（実施例３）
ＡＴＯ分散体（３）４２５質量部と蒸留水１７１７質量部をプラスチック容器に秤量し、高速攪拌機（プライミクス株式会社製ＴＫロボミックス）で攪拌（１４００ｒｐｍ）させながら、前もって調製した水系バインダー（１）１０％水溶液１００質量部を５分間かけて添加した。更に、添加後１５分間、１４００ｒｐｍで攪拌し、実施例３の保護層形成用組成物（ＡＴＯ粒子／水系バインダー＝８９．７／１０．３）を得た。実施例３の保護層形成用組成物の分散粒径Ｄ５０は１７７ｎｍで、経時安定性（２５℃、１週間）も良好であった。
(Example 3)
425 parts by weight of ATO dispersion (3) and 1717 parts by weight of distilled water were weighed in a plastic container and agitated (1400 rpm) with a high-speed stirrer (TK Robotics manufactured by Primix Co., Ltd.) to prepare an aqueous binder (1) 10 prepared in advance. 100 parts by mass of a 5% aqueous solution was added over 5 minutes. Furthermore, it stirred at 1400 rpm for 15 minutes after addition, and obtained the composition for protective layer formation of Example 3 (ATO particle / water-based binder = 89.7 / 10.3). Dispersion particle diameter D 50 of the protective layer-forming composition of Example 3 at 177 nm, stability over time (25 ° C., 1 week) was also good.
実施例３の保護層形成用組成物を使用した以外は、実施例１の集電体と同様にして実施例３の集電体を形成した。実施例３の集電体において保護層の厚みは２００ｎｍであった。 The current collector of Example 3 was formed in the same manner as the current collector of Example 1 except that the composition for forming a protective layer of Example 3 was used. In the current collector of Example 3, the thickness of the protective layer was 200 nm.
図３に実施例３の集電体の表面を走査型電子顕微鏡（ＳＥＭ）の観察結果を示す。図３にみられるように、実施例３の集電体の表面にある保護層において針状形状の導電性粒子が均一に分散されていることが観察された。また実施例３の集電体の表面を光学顕微鏡で観察したところ、干渉縞が観察されなかった。このことから実施例３の集電体の表面は表面平滑性が高く、表面の高低差が１００ｎｍ未満であることがわかった。 FIG. 3 shows the results of observation of the surface of the current collector of Example 3 with a scanning electron microscope (SEM). As can be seen in FIG. 3, it was observed that the needle-shaped conductive particles were uniformly dispersed in the protective layer on the surface of the current collector of Example 3. Moreover, when the surface of the electrical power collector of Example 3 was observed with the optical microscope, the interference fringe was not observed. From this, it was found that the surface of the current collector of Example 3 had high surface smoothness, and the surface height difference was less than 100 nm.
（実施例４）
ＡＴＯ分散体（１）５００質量部と蒸留水１４１０質量部をプラスチック容器に秤量し、高速攪拌機（プライミクス株式会社製ＴＫロボミックス）で攪拌（１４００ｒｐｍ）させながら、前もって調製した水系バインダー（２）１０％水溶液１００質量部を５分間かけて添加した。更に、添加後１５分間、１４００ｒｐｍで攪拌し、実施例４の保護層形成用組成物（ＡＴＯ粒子／バインダー＝８９．７／１０．３）を得た。実施例４の保護層形成用組成物の分散粒径Ｄ５０は１０５ｎｍで、経時安定性（２５℃、１週間）も良好であった。
Example 4
500 parts by weight of ATO dispersion (1) and 1410 parts by weight of distilled water were weighed in a plastic container and stirred in advance (1400 rpm) with a high-speed stirrer (TK Robotics manufactured by Primics Co., Ltd.). 100 parts by mass of a 5% aqueous solution was added over 5 minutes. Furthermore, it stirred at 1400 rpm for 15 minutes after addition, and obtained the composition for protective layer formation of Example 4 (ATO particle / binder = 89.7 / 10.3). The dispersion particle diameter D 50 of the composition for forming a protective layer of Example 4 was 105 nm, and the stability over time (25 ° C., 1 week) was also good.
実施例４の保護層形成用組成物を使用した以外は、実施例１の集電体と同様にして実施例４の集電体を形成した。実施例４の集電体において保護層の厚みは１００ｎｍであった。 The current collector of Example 4 was formed in the same manner as the current collector of Example 1 except that the composition for forming a protective layer of Example 4 was used. In the current collector of Example 4, the thickness of the protective layer was 100 nm.
（比較例１）
添加順序と混合条件を以下のように変更した以外は実施例１と同様にして、比較例１の保護層形成組成物を調製した。
(Comparative Example 1)
A protective layer forming composition of Comparative Example 1 was prepared in the same manner as in Example 1 except that the addition order and mixing conditions were changed as follows.
水系バインダー（１）１０％水溶液１００質量部と蒸留水１４１０質量部とをプラスチック容器に秤量し、マグネチックスターラーを用い攪拌（５００ｒｐｍ）させながら、ＡＴＯ分散体（１）５００質量部を５分間かけて添加した。更に、添加後２時間、５００ｒｐｍで攪拌して、比較例１の保護層形成用組成物（ＡＴＯ粒子／水系バインダー＝８９．７／１０．３）を得た。比較例１の保護層形成用組成物の分散粒径Ｄ５０は５９１ｎｍで、静置すると沈降物が確認された。 Aqueous binder (1) 100 parts by mass of 10% aqueous solution and 1410 parts by mass of distilled water are weighed in a plastic container and stirred with a magnetic stirrer (500 rpm), and 500 parts by mass of ATO dispersion (1) is applied over 5 minutes. Added. Furthermore, it stirred at 500 rpm for 2 hours after addition, and obtained the composition for protective layer formation of Comparative Example 1 (ATO particle / water-based binder = 89.7 / 10.3). Dispersion particle diameter D 50 of the protective layer-forming composition of Comparative Example 1 is 591 nm, sediment upon standing was confirmed.
比較例１の保護層形成用組成物を使用した以外は、実施例１の集電体と同様にして比較例１の集電体を形成した。比較例１の保護層形成用組成物は沈降物が存在したため、集電体本体に比較例１の保護層形成用組成物の均一な塗工はできなかった。 The current collector of Comparative Example 1 was formed in the same manner as the current collector of Example 1 except that the protective layer forming composition of Comparative Example 1 was used. Since a precipitate was present in the protective layer forming composition of Comparative Example 1, uniform coating of the protective layer forming composition of Comparative Example 1 was not possible on the current collector body.
比較例１においては、混合順序が逆であり、攪拌速度が５００ｒｐｍであることによってＡＴＯ分散体の分散状態を維持できなかったことがわかった。 In Comparative Example 1, it was found that the dispersion state of the ATO dispersion could not be maintained because the mixing order was reversed and the stirring speed was 500 rpm.
（比較例２）
添加順序を以下のように変更した以外は実施例１と同様にして比較例２の保護層形成用組成物を調製した。
(Comparative Example 2)
A protective layer forming composition of Comparative Example 2 was prepared in the same manner as in Example 1 except that the addition order was changed as follows.
水系バインダー（１）１０％水溶液１００質量部と蒸留水１４１０質量部とをプラスチック容器に秤量し、高速攪拌機（プライミクス株式会社製ＴＫロボミックス）で攪拌（１４００ｒｐｍ）させながら、ＡＴＯ分散体（１）５００質量部を５分間かけて添加した。更に、添加後１５分間、１４００ｒｐｍで攪拌して、比較例２の保護層形成用組成物（ＡＴＯ粒子／バインダー＝８９．７／１０．３）を得た。比較例２の保護層形成用組成物の分散粒径Ｄ５０は１０３ｎｍであったが、２５℃１週間保持後の比較例２の保護層形成用組成物の分散粒径Ｄ５０は２３０ｎｍであり、経時安定性（２５℃、１週間）において凝集傾向であった。 ATO dispersion (1) while weighing 100 parts by weight of aqueous binder (1) 10% aqueous solution and 1410 parts by weight of distilled water in a plastic container and stirring (1400 rpm) with a high-speed stirrer (TK Robotics manufactured by Primics Co., Ltd.) 500 parts by weight were added over 5 minutes. Furthermore, it stirred at 1400 rpm for 15 minutes after addition, and obtained the composition for protective layer formation of Comparative Example 2 (ATO particle / binder = 89.7 / 10.3). Dispersion particle diameter D 50 of the protective layer-forming composition of Comparative Example 2 is a was the 103 nm, dispersed particle diameter D 50 of the protective layer-forming composition of Comparative Example 2 after 25 ° C. 1 week holding is an 230nm , There was a tendency of aggregation in stability over time (25 ° C., 1 week).
比較例２の保護層形成用組成物を使用した以外は、実施例１の集電体と同様にして比較例２の集電体を形成した。比較例２の保護層形成用組成物は凝集傾向があったため、集電体本体に比較例２の保護層形成用組成物の均一な塗工はできなかった。 A current collector of Comparative Example 2 was formed in the same manner as the current collector of Example 1 except that the protective layer forming composition of Comparative Example 2 was used. Since the composition for forming a protective layer of Comparative Example 2 had a tendency to agglomerate, a uniform coating of the composition for forming a protective layer of Comparative Example 2 could not be performed on the current collector body.
比較例２においては、混合条件は同じであっても、混合順序が逆であることによってＡＴＯ分散体の分散状態を維持できなかったことがわかった。 In Comparative Example 2, it was found that even if the mixing conditions were the same, the dispersion state of the ATO dispersion could not be maintained due to the reverse mixing order.
＜正極の作成＞
（実施例１の正極）
まず正極活物質としてＬｉＮｉ０．５Ｃｏ０．２Ｍｎ０．３Ｏ２と導電助剤としてアセチレンブラックと、結着剤としてポリフッ化ビニリデン（ＰＶＤＦ）とを、それぞれ９４質量部、３質量部、３質量部として混合し、この混合物を適量のＮ−メチル−２−ピロリドン（ＮＭＰ）に分散させて、正極活物質層用スラリーを作製した。
<Creation of positive electrode>
(Positive electrode of Example 1)
First, LiNi 0.5 Co 0.2 Mn 0.3 O 2 as a positive electrode active material, acetylene black as a conductive additive, and polyvinylidene fluoride (PVDF) as a binder, 94 parts by mass, 3 parts by mass, The mixture was mixed as 3 parts by mass, and this mixture was dispersed in an appropriate amount of N-methyl-2-pyrrolidone (NMP) to prepare a slurry for a positive electrode active material layer.
上記実施例１の集電体に正極活物質層用スラリーをのせ、ドクターブレードを用いてスラリーが膜状になるように実施例１の集電体に塗布した。スラリーを塗布した集電体を８０℃で２０分間乾燥してＮＭＰを揮発させて除去した後、ロ−ルプレス機により、実施例1の集電体と実施例1の集電体上の塗布物を強固に密着接合させた。この時電極目付けは３．０ｇ／ｃｍ２となるようにした。接合物を１２０℃で６時間、真空乾燥機で加熱し、所定の形状（２５ｍｍ×３０ｍｍの矩形状）に切り取り、厚さ５０μm程度の正極とした。これを実施例１の正極とした。 The positive electrode active material layer slurry was placed on the current collector of Example 1 and applied to the current collector of Example 1 so that the slurry became a film using a doctor blade. After the current collector coated with the slurry was dried at 80 ° C. for 20 minutes to volatilize and remove NMP, the current collector of Example 1 and the coated material on the current collector of Example 1 were collected using a roll press. Were tightly bonded. At this time, the electrode weight was set to 3.0 g / cm 2 . The joined product was heated with a vacuum dryer at 120 ° C. for 6 hours, cut into a predetermined shape (rectangular shape of 25 mm × 30 mm), and formed into a positive electrode having a thickness of about 50 μm. This was used as the positive electrode of Example 1.
図４に実施例１の正極の断面の走査型電子顕微鏡（ＳＥＭ）の観察結果を示す。図４には、説明用の符号を付記した。図４に記載のように、集電体本体１には保護層２が配置され、保護層２の上に正極活物質層４が配置されていた。図４より、実施例１の正極において、保護層２の厚みは均一であることがわかった。また図４において保護層２の上に正極活物質層４は大きな隙間なく配置されていることがわかった。 FIG. 4 shows the observation result of the cross section of the positive electrode of Example 1 with a scanning electron microscope (SEM). In FIG. 4, reference numerals for explanation are added. As shown in FIG. 4, the protective layer 2 is disposed on the current collector body 1, and the positive electrode active material layer 4 is disposed on the protective layer 2. From FIG. 4, it was found that in the positive electrode of Example 1, the thickness of the protective layer 2 was uniform. In FIG. 4, it was found that the positive electrode active material layer 4 was disposed on the protective layer 2 without a large gap.
＜ラミネート型リチウムイオン二次電池作製＞
（実施例１のラミネート型リチウムイオン二次電池）
実施例１の正極を用いた実施例１のラミネート型リチウムイオン二次電池を次のようにして作製した。
<Production of laminated lithium-ion secondary battery>
(Laminated lithium ion secondary battery of Example 1)
A laminated lithium ion secondary battery of Example 1 using the positive electrode of Example 1 was produced as follows.
負極は以下のように作製した。黒鉛粉末９７質量部と、導電助剤としてアセチレンブラック１質量部と、結着剤として、スチレン−ブタジエンゴム（ＳＢＲ）１質量部、カルボキシメチルセルロース（ＣＭＣ）１質量部とを混合し、この混合物を適量のイオン交換水に分散させてスラリーを作製した。このスラリーを負極用集電体である厚み２０μｍの銅箔にドクターブレードを用いて膜状になるように塗布し、スラリーを塗布した集電体を乾燥後プレスし、接合物を１２０℃で６時間、真空乾燥機で加熱し、所定の形状（２５ｍｍ×３０ｍｍの矩形状）に切り取り、厚さ４５μm程度の負極とした。 The negative electrode was produced as follows. 97 parts by mass of graphite powder, 1 part by mass of acetylene black as a conductive additive, 1 part by mass of styrene-butadiene rubber (SBR) and 1 part by mass of carboxymethylcellulose (CMC) as a binder are mixed, and this mixture is mixed. A slurry was prepared by dispersing in an appropriate amount of ion-exchanged water. This slurry was applied to a copper foil having a thickness of 20 μm as a negative electrode current collector so as to form a film using a doctor blade, and the current collector coated with the slurry was dried and pressed. It was heated with a vacuum dryer for a time, cut into a predetermined shape (rectangular shape of 25 mm × 30 mm), and a negative electrode having a thickness of about 45 μm was obtained.
上記の正極および負極を用いて、ラミネート型リチウムイオン二次電池を製作した。詳しくは、正極および負極の間に、セパレータとしてポリプロピレン樹脂からなる矩形状シート（２７×３２ｍｍ、厚さ２５μｍ）を挟装して極板群とした。この極板群を二枚一組のラミネートフィルムで覆い、三辺をシールした後、袋状となったラミネートフィルムに電解液を注入した。電解液としてエチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）をＥＣ：ＤＥＣ＝３：７（体積比）で混合した溶媒に１モルのＬｉＰＦ６を溶解した溶液を用いた。その後、残りの一辺をシールすることで、四辺が気密にシールされ、極板群および電解液が密閉されたラミネート型リチウムイオン二次電池を得た。なお、正極および負極は外部と電気的に接続可能なタブを備え、このタブの一部はラミネート型リチウムイオン二次電池の外側に延出している。以上の工程で、実施例１のラミネート型リチウムイオン二次電池を作製した。 A laminate type lithium ion secondary battery was manufactured using the positive electrode and the negative electrode. Specifically, a rectangular sheet (27 × 32 mm, thickness 25 μm) made of polypropylene resin as a separator was sandwiched between the positive electrode and the negative electrode to form an electrode plate group. The electrode plate group was covered with a set of two laminated films, and the three sides were sealed, and then an electrolyte solution was injected into the bag-like laminated film. As an electrolytic solution, a solution obtained by dissolving 1 mol of LiPF 6 in a solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at EC: DEC = 3: 7 (volume ratio) was used. Thereafter, the remaining one side was sealed to obtain a laminate type lithium ion secondary battery in which the four sides were hermetically sealed and the electrode plate group and the electrolyte were sealed. Note that the positive electrode and the negative electrode have a tab that can be electrically connected to the outside, and a part of the tab extends to the outside of the laminated lithium ion secondary battery. The laminated lithium ion secondary battery of Example 1 was produced through the above steps.
このようにＡＴＯが均一に分散された保護層が形成できたので、実施例１のラミネート型リチウムイオン二次電池は、アルミニウム箔の保護層の保護効果が高いものと推測する。 Thus, since the protective layer in which ATO was uniformly dispersed could be formed, the laminate type lithium ion secondary battery of Example 1 is presumed to have a high protective effect on the protective layer of the aluminum foil.
１：集電体本体、２：保護層、３：リチウムイオン二次電池用集電体、４：正極活物質層。 1: current collector body, 2: protective layer, 3: current collector for lithium ion secondary battery, 4: positive electrode active material layer.
Claims (9)
アルミニウム箔からなる集電体本体に前記保護層形成用組成物を塗布し、乾燥して前記集電体本体の表面に保護層を形成する保護層形成工程と、
を有することを特徴とする集電体本体への保護層形成方法。 An aqueous binder of conductive particles comprising antimony-doped tin oxide (ATO) or antimony-doped tin oxide (ATO) -coated oxide is dispersed in the aqueous dispersion of conductive particles while stirring with a stirrer at a rotation speed of 1000 rpm or more. A protective layer-forming composition preparation step of preparing a protective layer-forming composition by mixing the aqueous dispersion of the conductive particles and the water-based binder-containing water by adding water.
A protective layer forming step of applying the protective layer forming composition to a current collector body made of aluminum foil and drying to form a protective layer on the surface of the current collector body;
A method for forming a protective layer on a current collector body, comprising:
前記保護層形成工程の前記アルミニウム箔は前記熱処理済みアルミニウム箔である請求項１〜５のいずれか一項に記載の集電体本体への保護層形成方法。 Before the protective layer forming step, further comprising a heat treatment step of aluminum foil to obtain a heat-treated aluminum foil by performing a heat treatment for holding the aluminum foil at 80 ° C. to 160 ° C. for 1 hour or more,
The method for forming a protective layer on a current collector body according to any one of claims 1 to 5, wherein the aluminum foil in the protective layer forming step is the heat-treated aluminum foil.
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