JP5939346B1 - Conductive composition, non-aqueous electrolyte secondary battery-coated current collector, non-aqueous electrolyte secondary battery electrode, and non-aqueous electrolyte secondary battery - Google Patents
Conductive composition, non-aqueous electrolyte secondary battery-coated current collector, non-aqueous electrolyte secondary battery electrode, and non-aqueous electrolyte secondary battery Download PDFInfo
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- JP5939346B1 JP5939346B1 JP2015220863A JP2015220863A JP5939346B1 JP 5939346 B1 JP5939346 B1 JP 5939346B1 JP 2015220863 A JP2015220863 A JP 2015220863A JP 2015220863 A JP2015220863 A JP 2015220863A JP 5939346 B1 JP5939346 B1 JP 5939346B1
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Classifications
-
- 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
Landscapes
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Cell Electrode Carriers And Collectors (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Conductive Materials (AREA)
- Electric Double-Layer Capacitors Or The Like (AREA)
Abstract
【課題】通常作動時の導電性に優れることから、電池の出力特性等に優れ、電池の内部温度が上昇した場合に、内部抵抗を上昇させる機能を備えた非水電解質二次電池(例えばリチウムイオン二次電池)を形成するための導電性組成物であって、非水電解質二次電池の導電性および安全機能に優れる導電性組成物を提供すること。【解決手段】前記課題は、導電性の炭素材料(A)と水溶性樹脂(B)と、水分散樹脂微粒子(C)と、水性液状媒体(D)とを含有する導電性組成物であって、前記水分散樹脂微粒子が少なくともオレフィン系樹脂微粒子を含むことを特徴とする導電性組成物によって解決される。【選択図】なしA non-aqueous electrolyte secondary battery (for example, a lithium ion battery) that has excellent conductivity during normal operation, has excellent battery output characteristics, and has a function of increasing internal resistance when the internal temperature of the battery increases. A conductive composition for forming an ion secondary battery), which is excellent in the conductivity and safety function of a nonaqueous electrolyte secondary battery. The object is a conductive composition containing a conductive carbon material (A), a water-soluble resin (B), water-dispersed resin fine particles (C), and an aqueous liquid medium (D). This is solved by a conductive composition in which the water-dispersed resin fine particles contain at least olefin resin fine particles. [Selection figure] None
Description
本発明は、導電性組成物、及びその組成物を用いて得られる非水電解質二次電池用電極、並びにその電極を用いて得られる非水電解質二次電池に関する。詳しくは、電池の温度が上昇した場合に該電池の内部抵抗を高くする機能を備えた導電性組成物、非水電解質二次電池用電極並びに非水電解質二次電池に関する。 The present invention relates to a conductive composition, an electrode for a nonaqueous electrolyte secondary battery obtained using the composition, and a nonaqueous electrolyte secondary battery obtained using the electrode. Specifically, the present invention relates to a conductive composition, a nonaqueous electrolyte secondary battery electrode, and a nonaqueous electrolyte secondary battery having a function of increasing the internal resistance of the battery when the temperature of the battery rises.
近年、デジタルカメラや携帯電話のような小型携帯型電子機器が広く用いられるようになってきた。これらの電子機器には、容積を最小限にし、かつ重量を軽くすることが常に求められてきており、搭載される電池においても、小型、軽量かつ大容量の電池の実現が求められている。特にリチウムイオン二次電池は鉛蓄電池、ニッカド電池、ニッケル水素電池等の水溶系二次電池と比較して大きなエネルギー密度が得られることから、パソコンや携帯端末等の電源としての重要性が高まっており、さらには車載搭載用高出力電源として好ましく用いられるものとして期待されている。 In recent years, small portable electronic devices such as digital cameras and mobile phones have been widely used. These electronic devices have always been required to minimize the volume and reduce the weight, and the batteries to be mounted are also required to be small, light, and have a large capacity. In particular, lithium-ion secondary batteries have a higher energy density than water-based secondary batteries such as lead-acid batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Therefore, they are becoming increasingly important as power sources for personal computers and mobile terminals. In addition, it is expected to be preferably used as a high-output power source mounted on a vehicle.
リチウムイオン二次電池は、エネルギー密度が高いという利点の反面、非水電解質を使用することから、安全性に対する十分な対応策が必要になる。近年、電池の大型化及び高容量化に応じて、安全性の確保が大きな課題となっている。例えば、過充電や電池内部での短絡等により、電池温度が異常に、かつ急激に上昇する場合、電池の外部に設けられた安全性機構だけでは、発熱を規制するのは困難となり、発火する危険性がある。 Lithium ion secondary batteries, while having the advantage of high energy density, use a non-aqueous electrolyte, so a sufficient countermeasure for safety is required. In recent years, ensuring the safety has become a major issue as the size and capacity of batteries increase. For example, if the battery temperature rises abnormally and suddenly due to overcharging or a short circuit inside the battery, it is difficult to control the heat generation with only the safety mechanism provided outside the battery, and it ignites. There is a risk.
特許文献1では、集電体に正温度係数抵抗体(以下PTC)の機能を有する電子伝導材料を接合する方法が記載されている。しかし、電子伝導性材料の厚みが50μmと厚いために、電池全体としてのエネルギー密度が低下し、好ましくない。 Patent Document 1 describes a method of joining an electron conductive material having a function of a positive temperature coefficient resistor (hereinafter referred to as PTC) to a current collector. However, since the thickness of the electron conductive material is as thick as 50 μm, the energy density of the entire battery is lowered, which is not preferable.
特許文献2では、正極、負極、非水電解液のいずれかにPTCの特性をもたせることが開示されている。しかし、これらにPTC特性を付与するには、電池容量に寄与しない多量の添加物を加える必要があり、エネルギー密度の低下が起こる。 Patent Document 2 discloses that any of a positive electrode, a negative electrode, and a non-aqueous electrolyte has PTC characteristics. However, in order to impart PTC characteristics to these, it is necessary to add a large amount of additives that do not contribute to battery capacity, resulting in a decrease in energy density.
特許文献3では、集電体表面に結晶性熱可塑性樹脂と導電剤および結着材からなる導電層を設ける方法が記載されている。この導電層は、電池内の温度が結晶性熱可塑性樹脂の融点を超えると、導電層の抵抗が上昇して、集電体と活物質間の電流が遮断される。しかし、電池の通常作動時における内部抵抗が高くなり、電池の出力特性が低下し、好ましくない。 Patent Document 3 describes a method of providing a conductive layer made of a crystalline thermoplastic resin, a conductive agent, and a binder on the surface of a current collector. In this conductive layer, when the temperature in the battery exceeds the melting point of the crystalline thermoplastic resin, the resistance of the conductive layer increases and the current between the current collector and the active material is interrupted. However, the internal resistance during normal operation of the battery is increased, and the output characteristics of the battery are deteriorated.
特許文献4では、集電体表面にポリフッ化ビニリデンと導電剤からなる導電層を設け、この導電層を設けた集電体を120℃を超える温度で加熱する方法が記載されている。しかし、熱処理する工程が追加されるほか、電池内の温度が上昇したときの抵抗上昇は十分でなく、好ましくない。 Patent Document 4 describes a method in which a conductive layer made of polyvinylidene fluoride and a conductive agent is provided on the current collector surface, and the current collector provided with the conductive layer is heated at a temperature exceeding 120 ° C. However, a heat treatment step is added, and the resistance rise when the temperature in the battery rises is not sufficient, which is not preferable.
特許文献5では、導電性粒子、カルボキシメチルセルロース、水分散オレフィン系樹脂および分散剤からなる導電層を設けた集電体を設ける方法が記載されている。しかし、カルボキシメチルセルロースは分散液の増粘剤として用いられ、その添加量は分散液の固形分の合計100質量%中、5質量%以下と少ない。 Patent Document 5 describes a method of providing a current collector provided with a conductive layer made of conductive particles, carboxymethyl cellulose, a water-dispersed olefin resin, and a dispersant. However, carboxymethylcellulose is used as a thickener for the dispersion, and its addition amount is as small as 5% by mass or less in a total of 100% by mass of the solid content of the dispersion.
特許文献6では、熱溶融性である粒子の体積平均粒子径が、導電性無機粒子の体積平均粒子径よりも大きい組成物からなる導電層を設ける方法が記載されている。しかし、電池内の温度が上昇したときの抵抗上昇は十分でなく、好ましくない。 Patent Document 6 describes a method of providing a conductive layer made of a composition in which the volume average particle diameter of particles that are heat-fusible is larger than the volume average particle diameter of conductive inorganic particles. However, the increase in resistance when the temperature in the battery rises is not sufficient, which is not preferable.
本発明の目的は、通常作動時の導電性に優れることから、電池の出力特性等に優れ、電池の内部温度が上昇した場合に、内部抵抗を上昇させる機能を備えた非水電解質二次電池(例えばリチウムイオン二次電池)を形成するための導電性組成物であって、非水電解質二次電池の導電性および安全機能に優れる導電性組成物を提供することである。 An object of the present invention is a non-aqueous electrolyte secondary battery having a function of increasing the internal resistance when the internal temperature of the battery is increased because of excellent electrical conductivity during normal operation, excellent battery output characteristics, etc. An object of the present invention is to provide a conductive composition for forming a lithium ion secondary battery (for example, a lithium ion secondary battery), which is excellent in the conductivity and safety function of a nonaqueous electrolyte secondary battery.
本発明は、導電性の炭素材料(A)と、水溶性樹脂(B)と、少なくともオレフィン系樹脂微粒子を含む水分散樹脂微粒子(C)とを含む導電性組成物であり、電池の発熱時に集電体の抵抗が増大し、電流を遮断することで、電池の発火等を回避するものである。また、発熱時に内部抵抗を増大させる樹脂が水分散樹脂微粒子であることから、炭素材料(A)の導電性を損なうことがなく、通常作動時の内部抵抗を低減でき、出力特性を改善することができる。 The present invention is a conductive composition comprising a conductive carbon material (A), a water-soluble resin (B), and water-dispersed resin fine particles (C) containing at least olefin-based resin fine particles. By increasing the resistance of the current collector and cutting off the current, ignition of the battery is avoided. In addition, since the resin that increases internal resistance during heat generation is water-dispersed resin fine particles, the electrical resistance of the carbon material (A) is not impaired, internal resistance during normal operation can be reduced, and output characteristics are improved. Can do.
さらに、本発明者は鋭意検討を行った結果、導電性組成物に含まれる水溶性樹脂(B)が、電池の内部温度が上昇した場合に、内部抵抗を上昇し続ける機能があることを知見し、本発明をなすに至った。
例えば、内部短絡などによって電池の内部温度が上昇した場合、導電性組成物に含まれるオレフィン系樹脂微粒子が、体積膨張することにより、導電性の炭素材料同士の接触を切断する。これにより、電極自体の抵抗が高くなるので、短絡箇所に流れる電流が減少し、ジュール発熱を抑制し、電池の安全性が保たれるという効果を奏すると考えられる。しかし、ポリオレフィン樹脂微粒子の体積膨張と同時に樹脂微粒子の溶融が起こり、炭素材料同士が再度接触して、電池の内部抵抗が十分上昇せず、安全性を保てなかった。
一方、導電性組成物に所定量の水溶性樹脂(B)を含むことで、上記オレフィン樹脂微粒子が溶融した場合でも、水溶性樹脂(B)が炭素同士の再接触を防ぐ効果が確認され、電池の安全性を飛躍的に向上させることがわかった。
さらには、水溶性樹脂(B)は導電性組成物(スラリー)において、化学的に安定であることから、経時変化が少なく、下地層を形成する際の塗工特性に優れる。
さらに、導電性の炭素材料の二次凝集粒子径を適切に制御することによって、上記、抵抗上昇をより効果的に行えることができ、電池の安全性を飛躍的に向上されることがわかった。
Furthermore, as a result of intensive studies, the inventor has found that the water-soluble resin (B) contained in the conductive composition has a function of continuously increasing the internal resistance when the internal temperature of the battery increases. Thus, the present invention has been made.
For example, when the internal temperature of the battery rises due to an internal short circuit or the like, the olefin-based resin fine particles contained in the conductive composition expand in volume, thereby cutting the contact between the conductive carbon materials. Thereby, since the resistance of the electrode itself is increased, it is considered that the current flowing through the short-circuited portion is reduced, the Joule heat generation is suppressed, and the battery safety is maintained. However, the resin fine particles were melted simultaneously with the volume expansion of the polyolefin resin fine particles, the carbon materials were brought into contact with each other again, and the internal resistance of the battery was not sufficiently increased, and safety could not be maintained.
On the other hand, by including a predetermined amount of the water-soluble resin (B) in the conductive composition, even when the olefin resin fine particles are melted, the effect of the water-soluble resin (B) preventing re-contact between carbons is confirmed. It has been found that the safety of the battery is dramatically improved.
Furthermore, since the water-soluble resin (B) is chemically stable in the conductive composition (slurry), there is little change over time, and the coating properties when forming the underlayer are excellent.
Furthermore, it was found that by appropriately controlling the secondary agglomerated particle size of the conductive carbon material, the above resistance increase can be performed more effectively, and the safety of the battery can be dramatically improved. .
さらに、水分散樹脂微粒子(C)の変性により、樹脂の溶融耐性を付与することができ、ポリオレフィン樹脂の体積膨張を維持し、炭素材料同士の接続の切断効果を維持し続けることができる。 Furthermore, modification | denaturation of water-dispersed resin microparticles | fine-particles (C) can provide the melt tolerance of resin, can maintain the volume expansion of polyolefin resin, and can maintain the cutting effect of the connection of carbon materials.
以上の効果によって、電池の安全性を飛躍的に向上させることがわかった。 It has been found that the above-described effects dramatically improve the safety of the battery.
即ち、本発明は、電性の炭素材料(A)と、水溶性樹脂(B)と、水分散樹脂微粒子(C)と、水性液状媒体(D)とを含有する非水電解質二次電池用電極の下地層形成用導電性組成物であって、前記水分散樹脂微粒子が少なくともオレフィン系樹脂微粒子を含み、導電性組成物の固形分の合計100質量%中、導電性の炭素材料(A)の含有量が、10〜50質量%であり、水溶性樹脂(B)の含有量が、510〜50質量%であり、水分散樹脂微粒子(C)の含有量が、30〜70質量%であり、水分散樹脂微粒子(C)に含まれるオレフィン系樹脂微粒子の割合が、50〜100質量%であることを特徴とする非水電解質二次電池用電極の下地層形成用導電性組成物に関する。
水分散樹脂微粒子(C)に含まれるオレフィン系樹脂微粒子が少なくともカルボン酸またはカルボン酸エステルで変性されたポリオレフィン樹脂粒子であり、ポリオレフィン樹脂粒子の赤外吸収スペクトルにおいて、2800〜3000cm-1の最大ピーク高さ(極大吸光度)(X)と、1690〜1740cm-1の最大ピーク高さ(極大吸光度)(Y)との比(Y)/(X)が0.05〜1.0であることを特徴とする上記非水電解質二次電池用電極の下地層形成用導電性組成物に関する。
水分散樹脂微粒子(C)に含まれるオレフィン系樹脂微粒子が少なくともカルボン酸またはカルボン酸エステルで変性されたポリエチレンからなり、前記(Y)/(X)が0.3〜0.8であることを特徴とする上記非水電解質二次電池用電極の下地層形成用導電性組成物に関する。
水分散樹脂微粒子(C)に含まれるオレフィン系樹脂微粒子が少なくともカルボン酸またはカルボン酸エステルで変性されたポリプロピレンからなり、前記(Y)/(X)が0.05〜0.5であることを特徴とする上記非水電解質二次電池用電極の下地層形成用導電性組成物に関する。
非水電解質二次電池用電極の下地層形成用導電性組成物が塗工された塗膜の光沢値が0.1〜33であることを特徴とする上記非水電解質二次電池用電極の下地層形成用導電性組成物に関する。
導電性の炭素材料(A)が、一次粒子が凝集して二次粒子が形成されたカーボンブラックであり、一次粒子径が1〜100nm、体積平均粒子径(D50)が0.3〜5μmであることを特徴とする上記非水電解質二次電池用電極の下地層形成用導電性組成物に関する。
前記カーボンブラックの体積平均粒子径が、水分散樹脂粒子(C)の体積平均粒子径よりも大きいことを特徴とする上記非水電解質二次電池用電極の下地層形成用導電性組成物に関する。
集電体と、上記非水電解質二次電池用電極の下地層形成用導電性組成物から形成された下地層とを有する非水電解質二次電池用下地層付き集電体に関する。
集電体と、上記非水電解質二次電池用電極の下地層形成用導電性組成物から形成された下地層と、電極活物質とバインダーとを含有する電極形成用組成物から形成された合材層とを有する非水電解質二次電池用電極に関する。
正極と負極と電解液とを具備する非水電解質二次電池であって、前記正極または前記負極の少なくとも一方が、上記非水電解質二次電池用電極である、非水電解質二次電池に関する。
That is, the present invention is for a non-aqueous electrolyte secondary battery containing an electric carbon material (A), a water-soluble resin (B), water-dispersed resin fine particles (C), and an aqueous liquid medium (D) . a foundation layer forming conductive composition of the electrode, the water-dispersible resin particles viewed contains at least an olefin resin particles, a total of 100 mass% of the solid of the conductive compositions partial, conductive carbon material (a ) Is 10 to 50% by mass, the content of the water-soluble resin (B) is 510 to 50% by mass, and the content of the water-dispersed resin fine particles (C) is 30 to 70% by mass. And the ratio of the olefin-based resin fine particles contained in the water-dispersed resin fine particles (C) is 50 to 100% by mass, the conductive composition for forming an underlayer of the electrode for a non-aqueous electrolyte secondary battery About .
The olefin resin fine particles contained in the water-dispersed resin fine particles (C) are polyolefin resin particles modified with at least a carboxylic acid or a carboxylic acid ester, and have a maximum peak of 2800 to 3000 cm −1 in the infrared absorption spectrum of the polyolefin resin particles. The ratio (Y) / (X) between the height (maximum absorbance) (X) and the maximum peak height (maximum absorbance) (Y) of 1690 to 1740 cm −1 is 0.05 to 1.0. It is related with the electroconductive composition for base layer formation of the electrode for the said nonaqueous electrolyte secondary battery characterized.
The olefin resin fine particles contained in the water-dispersed resin fine particles (C) are made of polyethylene modified with at least a carboxylic acid or a carboxylic acid ester, and (Y) / (X) is 0.3 to 0.8. It is related with the electroconductive composition for base layer formation of the electrode for the said nonaqueous electrolyte secondary battery characterized.
The olefin resin fine particles contained in the water-dispersed resin fine particles (C) are made of polypropylene modified with at least a carboxylic acid or a carboxylic acid ester, and (Y) / (X) is 0.05 to 0.5. It is related with the electroconductive composition for base layer formation of the electrode for the said nonaqueous electrolyte secondary battery characterized.
The gloss value of the coating film coated with the conductive composition for forming the underlayer of the electrode for a nonaqueous electrolyte secondary battery is 0.1 to 33 . The present invention relates to a conductive composition for forming an underlayer .
The conductive carbon material (A) is carbon black in which primary particles are aggregated to form secondary particles, the primary particle size is 1 to 100 nm, and the volume average particle size (D50) is 0.3 to 5 μm. It is related with the conductive composition for base layer formation of the said electrode for non-aqueous electrolyte secondary batteries characterized by the above-mentioned.
The volume average particle diameter of the carbon black is larger than the volume average particle diameter of the water-dispersed resin particles (C), and the present invention relates to the conductive composition for forming an underlayer of the electrode for a non-aqueous electrolyte secondary battery .
The present invention relates to a current collector with a base layer for a nonaqueous electrolyte secondary battery, comprising a current collector and a base layer formed from the conductive composition for forming the base layer of the electrode for a nonaqueous electrolyte secondary battery.
A composite formed from a current collector, a base layer formed from the conductive composition for forming the base layer of the electrode for a nonaqueous electrolyte secondary battery, and an electrode forming composition containing an electrode active material and a binder. The present invention relates to a non-aqueous electrolyte secondary battery electrode having a material layer.
The present invention relates to a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and an electrolyte solution, wherein at least one of the positive electrode and the negative electrode is the electrode for the non-aqueous electrolyte secondary battery.
導電性の炭素材料(A)と、水溶性樹脂(B)と、少なくともオレフィン系樹脂微粒子を含む水分散樹脂微粒子(C)とを含むことにより、炭素材料の導電性を損ねることなく、電池の内部温度が上昇した場合に、内部抵抗を上昇させる機能を備えた非水電解質二次電池を提供できる。 By containing the conductive carbon material (A), the water-soluble resin (B), and the water-dispersed resin fine particles (C) containing at least olefin resin fine particles, the conductivity of the carbon material is not impaired. A nonaqueous electrolyte secondary battery having a function of increasing internal resistance when the internal temperature rises can be provided.
<導電性組成物>
前記したように、本発明の導電性組成物は、非水電解質二次電池の下地層形成用として使用できる。導電性組成物は、導電性の炭素材料(A)と水溶性樹脂バインダー(B)と、少なくともオレフィン系樹脂微粒子を含む水分散樹脂微粒子(C)と、水性液状媒体(D)とを含有する。
導電性組成物の固形分の合計100質量%中、導電性の炭素材料(A)の含有量は、導電性と内部抵抗の観点から、10〜50質量%であり、好ましくは15〜50質量%、より好ましくは20〜40質量%である。
導電性組成物の固形分の合計100質量%中、水溶性樹脂(B)の含有量は、電極の密着性と導電性、および発熱時における電池の内部抵抗上昇の観点から、10〜50質量%であり、好ましくは10〜40質量%であり、より好ましくは15〜35質量%である。
導電性組成物の固形分の合計100質量%中、水分散樹脂微粒子(C)の含有量は、内部抵抗と導電性、および発熱時における電池の内部抵抗上昇の観点から、30〜70質量%であり、好ましくは30〜60質量%、より好ましくは35〜60質量%である。
また、導電性組成物の適正粘度は、導電性組成物の塗工方法によるが、一般には、10mPa・s以上、30,000mPa・s以下とするのが好ましい。
<Conductive composition>
As described above, the conductive composition of the present invention can be used for forming a base layer of a nonaqueous electrolyte secondary battery. The conductive composition contains a conductive carbon material (A), a water-soluble resin binder (B), water-dispersed resin fine particles (C) containing at least olefin resin fine particles, and an aqueous liquid medium (D). .
Total 100 mass% of the solid content of the conductive composition, the content of the conductive carbon material (A), from the viewpoint of conductivity and the internal resistance is 10 to 50 wt%, preferably from 15 to 50 weight %, More preferably 20 to 40% by mass.
The content of the water-soluble resin (B) in the total solid content of 100% by mass of the conductive composition is 10 to 50 masses from the viewpoint of electrode adhesion and conductivity, and increase in internal resistance of the battery during heat generation. % , Preferably 10 to 40% by mass, more preferably 15 to 35% by mass.
The content of the water-dispersed resin fine particles (C) in the total solid content of 100% by mass of the conductive composition is 30 to 70% by mass from the viewpoint of internal resistance and conductivity, and increase in internal resistance of the battery during heat generation. and is a preferably 30 to 60 wt%, more preferably 35 to 60 wt%.
Moreover, although the appropriate viscosity of an electroconductive composition is based on the coating method of an electroconductive composition, generally it is preferable to set it as 10 mPa * s or more and 30,000 mPa * s or less.
まず、導電性の炭素材料(A)について説明する。
本発明における導電性の炭素材料(A)としては、導電性を有する炭素材料であれば特に限定されるものではないが、グラファイト、カーボンブラック、導電性炭素繊維(カーボンナノチューブ、カーボンナノファイバー、カーボンファイバー)、フラーレン等を単独で、もしくは2種類以上併せて使用することができる。導電性、入手の容易さ、およびコスト面から、カーボンブラックの使用が好ましい。
First, the conductive carbon material (A) will be described.
The conductive carbon material (A) in the present invention is not particularly limited as long as it is a conductive carbon material, but graphite, carbon black, conductive carbon fiber (carbon nanotube, carbon nanofiber, carbon Fiber), fullerene, etc. can be used alone or in combination of two or more. From the viewpoint of conductivity, availability, and cost, it is preferable to use carbon black.
カーボンブラックとしては、気体もしくは液体の原料を反応炉中で連続的に熱分解し製造するファーネスブラック、特にエチレン重油を原料としたケッチェンブラック、原料ガスを燃焼させて、その炎をチャンネル鋼底面にあて急冷し析出させたチャンネルブラック、ガスを原料とし燃焼と熱分解を周期的に繰り返すことにより得られるサーマルブラック、特にアセチレンガスを原料とするアセチレンブラックなどの各種のものを単独で、もしくは2種類以上併せて使用することができる。また、通常行われている酸化処理されたカーボンブラックや、中空カーボン等も使用できる。 Carbon black is a furnace black produced by continuously pyrolyzing a gas or liquid raw material in a reactor, especially ketjen black using ethylene heavy oil as a raw material. Channel black that has been rapidly cooled and precipitated, thermal black obtained by periodically repeating combustion and thermal decomposition using gas as a raw material, and particularly various types such as acetylene black using acetylene gas as a raw material, or 2 More than one type can be used in combination. Ordinarily oxidized carbon black, hollow carbon and the like can also be used.
カーボンの酸化処理は、カーボンを空気中で高温処理したり、硝酸や二酸化窒素、オゾン等で二次的に処理したりすることより、例えばフェノール基、キノン基、カルボキシル基、カルボニル基の様な酸素含有極性官能基をカーボン表面に直接導入(共有結合)する処理であり、カーボンの分散性を向上させるために一般的に行われている。しかしながら、官能基の導入量が多くなる程カーボンの導電性が低下することが一般的であるため、酸化処理をしていないカーボンの使用が好ましい。 The oxidation treatment of carbon is performed by treating carbon at a high temperature in the air or by secondary treatment with nitric acid, nitrogen dioxide, ozone, etc., for example, such as phenol group, quinone group, carboxyl group, carbonyl group. This is a treatment for directly introducing (covalently bonding) an oxygen-containing polar functional group to the carbon surface, and is generally performed to improve the dispersibility of carbon. However, since it is common for the conductivity of carbon to fall, so that the introduction amount of a functional group increases, it is preferable to use the carbon which has not been oxidized.
また、本発明で用いるカーボンブラックは、一次粒子径が小さいほど単位質量当たりに含まれる粒子個数が増え、カーボンブラック粒子同士の接触点が増えるため、電極の内部抵抗を下げるのに有利となる。具体的には、導電性と入手のし易さの観点から、好ましくは1〜100nmであり、より好ましくは10〜80nmであり、さらに好ましくは20〜70nmである。 ただし、ここでいう一次粒子径とは、アグリゲート(一次凝集体)を形成する球形粒子であり、電子顕微鏡などで測定された粒子径を平均したものである。 In addition, the carbon black used in the present invention is advantageous in decreasing the internal resistance of the electrode because the number of particles contained per unit mass increases as the primary particle diameter decreases, and the number of contact points between the carbon black particles increases. Specifically, from the viewpoint of conductivity and availability, it is preferably 1 to 100 nm, more preferably 10 to 80 nm, and even more preferably 20 to 70 nm. However, the primary particle diameter here is a spherical particle forming an aggregate (primary aggregate), and is an average of particle diameters measured with an electron microscope or the like.
本発明で用いられるカーボンブラックは、アグリゲート(一次凝集体)が凝集してなるアグロメレート(二次凝集体)を形成している。二次凝集体のサイズが所定以上大きいことで、導電ネットワークを形成しやすくなり、電極の内部抵抗を下げるのに有利となる。また、本発明において、鋭意検討を重ねた結果、カーボンブラックが所定の二次凝集体を形成することで、電池の内部温度が上昇した場合、電池の内部抵抗が大きくなることが明らかとなった。本発明において、二次凝集体は体積平均粒子径で表され、具体的には体積平均粒子径(D50)が好ましくは0.3〜5μmであり、より好ましくは0.3〜3μmである。
ここでいう分散粒径とは、体積粒度分布において、粒子径の細かいものからその粒子の体積割合を積算していったときに、50%となるところの粒子径(D50)であり、一般的な粒度分布計、例えば、レーザー散乱方式の粒度分布計(日機装社製「マイクロトラックMT3300EXII」)等で測定される。レーザー散乱法による体積平均粒子径の測定は、以下のようにして行うことができる。導電性の炭素材料(A)と水溶性樹脂(B)を機械分散したスラリーを、固形分に応じて100〜1000倍に水希釈しておく。測定装置 [(株)日機装製 マイクロトラックMT3300EXII]のセルに該希釈スラリーをサンプリングローディングにおいて適正濃度になるまで注入し、サンプルに応じた溶剤(本発明では水)の屈折率条件を入力後、測定を行う。
The carbon black used in the present invention forms an agglomerate (secondary aggregate) formed by aggregating aggregates (primary aggregates). When the size of the secondary aggregate is larger than a predetermined size, it becomes easy to form a conductive network, which is advantageous in reducing the internal resistance of the electrode. Further, in the present invention, as a result of intensive studies, it was found that the internal resistance of the battery increases when the internal temperature of the battery rises due to the carbon black forming a predetermined secondary aggregate. . In the present invention, the secondary aggregate is represented by a volume average particle diameter. Specifically, the volume average particle diameter (D50) is preferably 0.3 to 5 μm, more preferably 0.3 to 3 μm.
The dispersed particle size referred to here is a particle size (D50) that is 50% when the volume ratio of the particles is integrated from the fine particle size distribution in the volume particle size distribution. A particle size distribution meter such as a laser scattering type particle size distribution meter (“MICROTRACK MT3300EXII” manufactured by Nikkiso Co., Ltd.) or the like. The volume average particle diameter can be measured by the laser scattering method as follows. A slurry obtained by mechanically dispersing a conductive carbon material (A) and a water-soluble resin (B) is diluted with water 100 to 1000 times depending on the solid content. Measurement device [Nikkiso Co., Ltd. Microtrac MT3300EXII] cell was poured into the cell until the appropriate concentration was obtained in sampling loading, and the refractive index condition of the solvent (water in the present invention) corresponding to the sample was input and measured. I do.
本発明で用いられるカーボンブラックの体積平均粒子径が、水分散樹脂微粒子(C)の体積平均粒子径よりも大きいことが好ましい。水分散樹脂微粒子(C)の体積平均粒子径がカーボンブラックの体積平均粒子径よりも大きいと、電池の内部温度が上昇した場合、効率よく電池の抵抗上昇がおこらなくなるほか、通常作動時の内部抵抗が上昇し、電池性能が悪化する場合がある。水分散樹脂微粒子(C)の体積平均粒子径の測定方法については、別途記載する。 The volume average particle size of the carbon black used in the present invention is preferably larger than the volume average particle size of the water-dispersed resin fine particles (C). If the volume average particle size of the water-dispersed resin fine particles (C) is larger than the volume average particle size of the carbon black, when the internal temperature of the battery rises, the resistance of the battery does not increase efficiently, and the internal during normal operation Resistance may increase and battery performance may deteriorate. A method for measuring the volume average particle diameter of the water-dispersed resin fine particles (C) will be described separately.
本発明で用いるカーボンブラックの比表面積は、一般的には値が大きいほど、カーボンブラックの一次粒子径が小さくなるため、粒子同士の接触点が増え、電極の内部抵抗を下げるのに有利となる。具体的には、導電性や塗工適性、電極密着性や入手のし易さの観点から、窒素の吸着量から求められる比表面積(BET)で、好ましくは20〜1500m2/g、より好ましくは40〜1500m2/gのものを使用することが望ましい。 The specific surface area of the carbon black used in the present invention is generally more advantageous as the value of the carbon black becomes smaller as the primary particle diameter of the carbon black decreases, increasing the contact point between the particles and lowering the internal resistance of the electrode. . Specifically, from the viewpoints of conductivity, coating suitability, electrode adhesion, and availability, the specific surface area (BET) determined from the amount of nitrogen adsorption, preferably 20-1500 m 2 / g, more preferably Is preferably 40 to 1500 m 2 / g.
市販のカーボンブラックとしては、例えば、トーカブラック#4300、#4400、#4500、#5500等(東海カーボン社製、ファーネスブラック)、プリンテックスL等(デグサ社製、ファーネスブラック)、Raven7000、5750、5250、5000ULTRAIII、5000ULTRA等、Conductex SC ULTRA
、Conductex 975 ULTRA等、PUER BLACK100、115、2
05等(コロンビヤン社製、ファーネスブラック)、#2350、#2400B、#2600B、#30050B、#3030B、#3230B、#3350B、#3400B、#5400B等(三菱化学社製、ファーネスブラック)、MONARCH1400、1300、900、VulcanXC−72R、BlackPearls2000等(キャボット社製、ファーネスブラック)、Ensaco250G、Ensaco260G、Ensaco350G、SuperP−Li(TIMCAL社製)、ケッチェンブラックEC−300J、EC−600JD(アクゾ社製)、デンカブラック、デンカブラックHS−100、FX−35(電気化学工業社製、アセチレンブラック)等、グラファイトとしては、例えば人造黒鉛や燐片状黒鉛、塊状黒鉛、土状黒鉛などの天然黒鉛が挙げられるが、これらに限定されるものではなく、2種以上を組み合わせて用いても良い。
導電性炭素繊維としては石油由来の原料から焼成して得られるものが良いが、植物由来の原料からも焼成して得られるものも用いることができる。例えば石油由来の原料で製造される昭和電工社製のVGCFなどを挙げることができる。
Examples of commercially available carbon black include Toka Black # 4300, # 4400, # 4500, # 5500 (Tokai Carbon Co., Furnace Black), Printex L and the like (Degussa Co., Furnace Black), Raven 7000, 5750, 5250, 5000 ULTRA III, 5000 ULTRA, etc., Conductex SC ULTRA
, Conductex 975 ULTRA, etc., PUER BLACK100, 115, 2
05, etc. (Colombian, Furnace Black), # 2350, # 2400B, # 2600B, # 30050B, # 3030B, # 3230B, # 3350B, # 3400B, # 5400B, etc. (Mitsubishi Chemical Corporation, Furnace Black), MONARCH1400, 1300, 900, Vulcan XC-72R, BlackPearls 2000, etc. (Cabot, Furnace Black), Ensaco 250G, Ensaco 260G, Ensaco 350G, SuperP-Li (manufactured by TIMCAL), Ketjen Black EC-300J, EC-600JD (manufactured by Akzo) Examples of graphite such as Denka Black, Denka Black HS-100, FX-35 (manufactured by Denki Kagaku Kogyo Co., Ltd., acetylene black) include artificial graphite and flakes. Lead, massive graphite, there may be mentioned natural graphite such as earthy graphite, is not limited thereto, it may be used in combination of two or more.
As the conductive carbon fibers, those obtained by firing from petroleum-derived raw materials are preferable, but those obtained by firing from plant-derived raw materials can also be used. For example, VGCF manufactured by Showa Denko Co., Ltd. manufactured with petroleum-derived raw materials can be mentioned.
次に、水溶性樹脂(B)について説明する。
本発明の水溶性樹脂(B)とは、25℃の水99g中に水溶性樹脂(B)1g入れて撹拌し、25℃で24時間放置した後、分離・析出せずに水中で樹脂が溶解可能なものである。
Next, water-soluble resin (B) is demonstrated.
The water-soluble resin (B) of the present invention is a mixture of 1 g of water-soluble resin (B) in 99 g of water at 25 ° C. and stirred for 24 hours at 25 ° C. It can be dissolved.
水溶性樹脂(B)としては、上述の通り水溶性を示す樹脂であれば特に限定されるものではないが、例えば、アクリル樹脂、ポリウレタン樹脂、ポリエステル樹脂、ポリアミド樹脂、ポリイミド樹脂、ポリアリルアミン樹脂、フェノール樹脂、エポキシ樹脂、フェノキシ樹脂、尿素樹脂、メラミン樹脂、アルキッド樹脂、ホルムアルデヒド樹脂、シリコン樹脂、ポリビニルアルコール樹脂、フッ素樹脂、カルボキシメチルセルロース等の多糖類の樹脂を含む高分子化合物が挙げられる。また、水溶性であれば、これらの樹脂の変性物、混合物、又は共重合体でも良い。これら水溶性樹脂は、1種または複数を組み合わせて使用することも出来る。
水溶性樹脂(B)の分子量は特に限定されないが、好ましくは質量平均分子量が5,000〜2,000,000である。質量平均分子量(Mw)とは、ゲルパーミエーションクロマトグラフィー(GPC)におけるポリエチレンオキサイド換算分子量を示す。
The water-soluble resin (B) is not particularly limited as long as it is a water-soluble resin as described above. For example, an acrylic resin, a polyurethane resin, a polyester resin, a polyamide resin, a polyimide resin, a polyallylamine resin, High molecular compounds containing polysaccharide resins such as phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, formaldehyde resin, silicon resin, polyvinyl alcohol resin, fluororesin, carboxymethyl cellulose, and the like. Moreover, if it is water-soluble, the modified substance, mixture, or copolymer of these resin may be sufficient. These water-soluble resins can be used alone or in combination.
The molecular weight of the water-soluble resin (B) is not particularly limited, but the mass average molecular weight is preferably 5,000 to 2,000,000. The mass average molecular weight (Mw) indicates the molecular weight in terms of polyethylene oxide in gel permeation chromatography (GPC).
また、本発明において、水溶性樹脂(B)はカルボキシメチルセルロースを用いることが好ましく、電池の内部温度が上昇したときの抵抗上昇の観点から、上記の質量平均分子量が10,000〜70,000であり、エーテル化度が0.3〜1.0であることがより好ましい。エーテル化は、灰化した試料を硫酸にて煮沸し、フェノールフタレイン指示薬に加え、過剰の酸を水酸化カリウムで逆滴定することにより求める。
さらに、カルボキシメチルセルロース1gを25℃の水99g中に入れて撹拌して得られた1質量%水溶液の粘度が0.01〜0.1Pa・sであることがより好ましい。水溶液の粘度測定はレオメーター(TAインスツルメント社製AR−G2)により、コーンプレート(60mm、1°)を用いて、測定温度25℃、せん断速度360(1/s)で測定したものである。
In the present invention, it is preferable to use carboxymethylcellulose as the water-soluble resin (B). From the viewpoint of increasing the resistance when the internal temperature of the battery is increased, the mass average molecular weight is 10,000 to 70,000. More preferably, the degree of etherification is 0.3 to 1.0. Etherification is determined by boiling the incinerated sample with sulfuric acid, adding it to the phenolphthalein indicator, and back titrating excess acid with potassium hydroxide.
Furthermore, it is more preferable that the viscosity of a 1% by mass aqueous solution obtained by stirring 1 g of carboxymethyl cellulose in 99 g of water at 25 ° C. is 0.01 to 0.1 Pa · s. The viscosity of the aqueous solution was measured with a rheometer (AR Instruments G2 manufactured by TA Instruments) using a cone plate (60 mm, 1 °) at a measurement temperature of 25 ° C. and a shear rate of 360 (1 / s). is there.
以上のようなカルボキシメチルセルロースは市販品を用いることが可能であり、市販品としては、例えば、ダイセル化学工業社製の#1110、#1120、#1130、#1140.#1170、#1210、#1240、#1250、#1260、#1270などが挙げられるが、これらに限定されるものではない。 Commercially available products can be used as the carboxymethylcellulose as described above. Examples of commercially available products include # 1110, # 1120, # 1130, # 1140. Examples include, but are not limited to, # 1170, # 1210, # 1240, # 1250, # 1260, and # 1270.
次に、水分散樹脂微粒子(C)について説明する。
本発明の水分散樹脂微粒子(C)としては、一般的に水性エマルションとも呼ばれるものであり、樹脂粒子が水中で溶解せずに、微粒子の形態で分散されているものである。
水分散樹脂微粒子は少なくともオレフィン系樹脂微粒子を含み、水分散樹脂微粒子に含まれるオレフィン系樹脂微粒子の割合が50〜100質量%であり、必要に応じて、オレフィン系樹脂微粒子以外の2種以上の水分散樹脂微粒子を組み合わせても良い。オレフィン系樹脂微粒子以外の水分散樹脂微粒子は特に限定されないが、(メタ)アクリル系エマルション、ニトリル系エマルション、ウレタン系エマルション、ジエン系エマルション(SBRなど)、フッ素系エマルション(PVDFやPTFEなど)等が挙げられる。
Next, the water-dispersed resin fine particles (C) will be described.
The water-dispersed resin fine particles (C) of the present invention are generally called water-based emulsions, and the resin particles are dispersed in the form of fine particles without being dissolved in water.
The water-dispersed resin fine particles include at least olefin-based resin fine particles, and the ratio of the olefin-based resin fine particles contained in the water-dispersed resin fine particles is 50 to 100% by mass. Water-dispersed resin fine particles may be combined. Water-dispersed resin fine particles other than olefin resin fine particles are not particularly limited, but (meth) acrylic emulsions, nitrile emulsions, urethane emulsions, diene emulsions (SBR, etc.), fluorine emulsions (PVDF, PTFE, etc.), etc. Can be mentioned.
水分散樹脂微粒子としては、80〜180℃の範囲内でオレフィン系樹脂が体積膨張して、導電層中に分散している導電性の炭素材料同士の接触を引き剥がすことができる樹脂であれば特に限定されるものではない。ポリオレフィン樹脂のオレフィン成分としては、例えば、エチレン、プロピレン、イソブチレン、イソブテン、1−ブテン、2−ブテン、1−ペンテン、4−メチル−1−ペンテン、3−メチル−1−ペンテンン、1−ヘキセン、1−オクテン、ノルボネン等が挙げられる。これらオレフィン成分単一の重合体でも良く、2成分以上の共重合体でも良い。また、電池の内部温度上昇時でのポリオレフィンの体積膨張を保持する効果から、カルボン酸やカルボン酸エステルを有する化合物での変性や共重合などを行っても良い。 As the water-dispersed resin fine particles, any resin can be used as long as the olefin-based resin expands in volume within a range of 80 to 180 ° C. and the contact between the conductive carbon materials dispersed in the conductive layer can be removed. It is not particularly limited. Examples of the olefin component of the polyolefin resin include ethylene, propylene, isobutylene, isobutene, 1-butene, 2-butene, 1-pentene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-hexene, Examples thereof include 1-octene and norbonene. A single polymer of these olefin components may be used, and a copolymer of two or more components may be used. Further, modification or copolymerization with a compound having a carboxylic acid or a carboxylic acid ester may be performed from the effect of maintaining the volume expansion of the polyolefin when the internal temperature of the battery rises.
本発明において、水分散樹脂微粒子(C)に含まれるオレフィン系樹脂微粒子が少なくともカルボン酸またはカルボン酸エステルを有する化合物で変性させることが好ましい。変性によって、樹脂の溶融耐性を付与できることから、内部短絡などによる電池の内部温度上昇時に、ポリオレフィン樹脂の体積膨張を維持することができ、炭素材料同士の切断効果を維持し続けることができると考えられる。 In the present invention, the olefin resin fine particles contained in the water-dispersed resin fine particles (C) are preferably modified with a compound having at least a carboxylic acid or a carboxylic acid ester. Since the resin can be given melt resistance by modification, the volume expansion of the polyolefin resin can be maintained when the internal temperature of the battery rises due to an internal short circuit or the like, and the cutting effect between the carbon materials can be maintained. It is done.
カルボン酸またはカルボン酸エステルの成分としては特に限定されないが、アクリル酸、メタクリル酸、無水マレイン酸、マレイン酸、無水イタコン酸、イタコン酸、フマル酸、クロトン酸、アクリル酸メチル、(メタ)アクリル酸メチル、(メタ)アクリル酸エチル、(メタ)アクリル酸プロピル、アクリル酸ブチル、(メタ)アクリル酸ヘキシル、(メタ)アクリル酸オクチル、(メタ)アクリル酸デシル、(メタ)アクリル酸ラウリル、(メタ)アクリル酸ドデシル、(メタ)アクリル酸ステアリル、ギ酸ビニル、酢酸ビニル、プロピオン酸ビニル、ピパリン酸ビニルなどが挙げられる。 Although it does not specifically limit as a component of carboxylic acid or carboxylic acid ester, Acrylic acid, methacrylic acid, maleic anhydride, maleic acid, itaconic anhydride, itaconic acid, fumaric acid, crotonic acid, methyl acrylate, (meth) acrylic acid Methyl, ethyl (meth) acrylate, propyl (meth) acrylate, butyl acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, (meth ) Dodecyl acrylate, stearyl (meth) acrylate, vinyl formate, vinyl acetate, vinyl propionate, vinyl piperate.
上記に変性されたポリオレフィン樹脂微粒子の変性量としては、フーリエ変換赤外分光装置(FT−IR:PerkinElmer社製Spectrum One/100)による全反射測定法(ATR)によって求めることができ、2800〜3000cm-1のオレフィン由来の最大ピーク高さ(極大吸光度)(X)と、1690〜1740cm-1のカルボニル由来の最大ピーク高さ(極大吸光度)(Y)との比(Y)/(X)が0.05〜1.0であることが好ましい。また、ポリエチレンからなる樹脂微粒子においては、上記(Y)/(X)が0.3〜0.8であり、ポリプロピレンからなる樹脂微粒子においては、上記(Y)/(X)が0.05〜0.5であることがさらに好ましい。
ここでいうピーク高さとは、水分散樹脂微粒子(C)から分散媒を除去し、最終的に120℃で乾燥させて得られた固形物をFT−IRにて測定したものである。ポリオレフィン樹脂微粒子の変性量は、波数に対して吸光度をプロットしたスペクトルを用い、2700m-1における吸光度を示す点と3000cm-1における吸光度を示す点との2点を結ぶ直線をベースラインBXとした際の、2800〜3000cm-1に見られるオレフィン由来の2本または4本のうち、最大ピークからベースラインBXまでの高さ(極大吸光度)(X)と、1650m-1における吸光度を示す点と1850cm-1における吸光度を示す点との2点を結ぶ直線をベースラインBYとした際の、1690〜1740cm-1のカルボニル由来の最大ピークからベースラインBYまでの高さ(極大吸光度)(Y)との比(Y)/(X)から求めることができる。一般的に、ポリエチレン系樹脂は2本、ポリプロピレン系樹脂は4本みられるが、両者とも最大ピークは2915cm-1付近に見られる。
The amount of modification of the polyolefin resin fine particles modified as described above can be determined by a total reflection measurement method (ATR) using a Fourier transform infrared spectrometer (FT-IR: Spectrum One / 100 manufactured by PerkinElmer), and can be determined from 2800 to 3000 cm. -1 olefin-derived maximum peak height (maximum absorbance) (X) and the carbonyl-derived maximum peak height (maximum absorbance) (Y) of 1690-1740 cm -1 (Y) / (X) It is preferable that it is 0.05-1.0. In the resin fine particles made of polyethylene, the above (Y) / (X) is 0.3 to 0.8, and in the resin fine particles made of polypropylene, the above (Y) / (X) is 0.05 to 0.8. More preferably, it is 0.5.
The peak height referred to here is a value obtained by measuring a solid obtained by removing the dispersion medium from the water-dispersed resin fine particles (C) and finally drying at 120 ° C. by FT-IR. The amount of modification of the polyolefin resin fine particles was determined by using a spectrum in which the absorbance was plotted against the wave number, and a line connecting the two points of the absorbance at 2700 m −1 and the absorbance at 3000 cm −1 was defined as the baseline BX. Among the two or four derived from olefins observed at 2800 to 3000 cm −1 , the height (maximum absorbance) (X) from the maximum peak to the baseline BX, and the point indicating the absorbance at 1650 m −1 Height from the maximum peak derived from the carbonyl of 1690 to 1740 cm -1 to the baseline BY (maximum absorbance) when the straight line connecting the two points with the point indicating the absorbance at 1850 cm -1 is defined as the baseline BY (Y) And the ratio (Y) / (X). In general, two polyethylene resins and four polypropylene resins are observed, and the maximum peak is observed in the vicinity of 2915 cm -1 in both cases.
以上のような水分散樹脂微粒子は市販品を用いることが可能であり、市販品としてはユニチカ社製のアローベースSB−1200、SD−1200、SE−1200、TC−4010、TD−4010、東洋アドレ社製のアクアペトロDP−2401、DP−2502、住友精化社製のザイクセンAC、A、AC−HW−10,L、NC、Nなど、三井化学社製のケミパールA100、A400、M200、S100、S200、S300V100、V200、V300、W100、W200、W300、W400、W4005、WP100、東洋紡社製のハードレンNZ−1004、NZ−1015、東邦化学社製ハイテックE−6500、P−9018、S−3121などが挙げられるが、これらに限定されるものではなく、2種以上を組み合わせて用いても良い。 Commercially available products can be used as the water-dispersed resin fine particles as described above, and commercially available products such as Arrow Base SB-1200, SD-1200, SE-1200, TC-4010, TD-4010, and Toyo made by Unitika. Aqua Petro DP-2401, DP-2502 manufactured by Adre, Seixen AC, A, AC-HW-10, L, NC, N manufactured by Sumitomo Seika Co., Ltd., Chemipearl A100, A400, M200 manufactured by Mitsui Chemicals, S100, S200, S300V100, V200, V300, W100, W200, W300, W400, W4005, WP100, Hardren NZ-1004, NZ-1015 manufactured by Toyobo, Hitech E-6500, P-9018, S-manufactured by Toho Chemical Co., Ltd. 3121 etc. are mentioned, but it is not limited to these. It may be used in conjunction seen.
本発明の水分散樹脂微粒子(C)の分散媒としては、水を使用することが好ましいが、樹脂微粒子の安定化等のために、水と相溶する液状媒体を使用しても良い。水と相溶する液状媒体としては、アルコール類、グリコール類、セロソルブ類、アミノアルコール類、アミン類、ケトン類、カルボン酸アミド類、リン酸アミド類、スルホキシド類、カルボン酸エステル類、リン酸エステル類、エーテル類、ニトリル類等が挙げられ、水と相溶する範囲で使用しても良い。 As the dispersion medium of the water-dispersed resin fine particles (C) of the present invention, water is preferably used, but a liquid medium compatible with water may be used for stabilizing the resin fine particles. Liquid media compatible with water include alcohols, glycols, cellosolves, amino alcohols, amines, ketones, carboxylic acid amides, phosphoric acid amides, sulfoxides, carboxylic acid esters, and phosphoric acid esters , Ethers, nitriles and the like, and may be used as long as they are compatible with water.
本発明の水分散樹脂微粒子(C)の平均粒子径は、好ましくは0.01〜5μmであり、さらに好ましくは0.05〜1μmである。粒子径が小さすぎると、安定に製造するのが困難となり、一方、粒子径が大きすぎると、導電層の導電性を均一に保つことが困難となり、通常作動時の内部抵抗が上昇し、電池性能が悪化する。 The average particle diameter of the water-dispersed resin fine particles (C) of the present invention is preferably 0.01 to 5 μm, more preferably 0.05 to 1 μm. If the particle size is too small, it will be difficult to produce stably, while if the particle size is too large, it will be difficult to keep the conductivity of the conductive layer uniform, the internal resistance during normal operation will increase, and the battery will Performance deteriorates.
なお、本発明における平均粒子径とは、体積平均粒子径(D50)のことを表し、動的光散乱法により測定できる。動的光散乱法による平均粒子径の測定は、以下のようにして行うことができる。水分散樹脂微粒子分散液は固形分に応じて200〜1000倍に水希釈しておく。該希釈液約5mlを測定装置[(株)日機装製 ナノトラック]のセルに注入し、サンプルに応じた溶剤(本発明では水)および樹脂の屈折率条件を入力後、測定を行う。 In addition, the average particle diameter in this invention represents a volume average particle diameter (D50), and can be measured by the dynamic light scattering method. The average particle diameter can be measured by the dynamic light scattering method as follows. The water-dispersed resin fine particle dispersion is diluted with water 200 to 1000 times depending on the solid content. About 5 ml of the diluted solution is injected into a cell of a measuring device [Nanotrack manufactured by Nikkiso Co., Ltd.], and after inputting the refractive index conditions of the solvent (water in the present invention) and the resin according to the sample, the measurement is performed.
つぎに、水性液状媒体(D)について説明する。
本発明に使用する水性液状媒体(D)としては、水を使用することが好ましいが、必要に応じて、例えば、集電体への塗工性向上のために、水と相溶する液状媒体を使用しても良い。
Next, the aqueous liquid medium (D) will be described.
As the aqueous liquid medium (D) used in the present invention, it is preferable to use water, but if necessary, for example, a liquid medium compatible with water in order to improve the coating property to the current collector. May be used.
水と相溶する液状媒体としては、アルコール類、グリコール類、セロソルブ類、アミノアルコール類、アミン類、ケトン類、カルボン酸アミド類、リン酸アミド類、スルホキシド類、カルボン酸エステル類、リン酸エステル類、エーテル類、ニトリル類等が挙げられ、水と相溶する範囲で使用しても良い。 Liquid media compatible with water include alcohols, glycols, cellosolves, amino alcohols, amines, ketones, carboxylic acid amides, phosphoric acid amides, sulfoxides, carboxylic acid esters, and phosphoric acid esters , Ethers, nitriles and the like, and may be used as long as they are compatible with water.
さらに、導電性組成物には、成膜助剤、消泡剤、レベリング剤、防腐剤、pH調整剤、粘性調整剤などを必要に応じて配合できる。 Furthermore, a film-forming auxiliary, an antifoaming agent, a leveling agent, a preservative, a pH adjusting agent, a viscosity adjusting agent and the like can be blended with the conductive composition as necessary.
(分散機・混合機)
本発明の導電性組成物や後述する合材インキを得る際に用いられる装置としては、顔料分散等に通常用いられている分散機、混合機が使用できる。
例えば、ディスパー、ホモミキサー、若しくはプラネタリーミキサー等のミキサー類;エム・テクニック社製「クレアミックス」、若しくはPRIMIX社「フィルミックス」等のホモジナイザー類;ペイントコンディショナー(レッドデビル社製)、ボールミル、サンドミル(シンマルエンタープライゼス社製「ダイノミル」等)、アトライター、パールミル(アイリッヒ社製「DCPミル」等)、若しくはコボールミル等のメディア型分散機;湿式ジェットミル(ジーナス社製「ジーナスPY」、スギノマシン社製「スターバースト」、ナノマイザー社製「ナノマイザー」等)、エム・テクニック社製「クレアSS−5」、若しくは奈良機械社製「MICROS」等のメディアレス分散機;または、その他ロールミル等が挙げられるが、これらに限定されるものではない。また、分散機としては、分散機からの金属混入防止処理を施したものを用いることが好ましい。
例えば、メディア型分散機を使用する場合は、アジテーター及びベッセルがセラミック製又は樹脂製の分散機を使用する方法や、金属製アジテーター及びベッセル表面をタングステンカーバイド溶射や樹脂コーティング等の処理をした分散機を用いることが好ましい。そして、メディアとしては、ガラスビーズ、または、ジルコニアビーズ、若しくはアルミナビーズ等のセラミックビーズを用いることが好ましい。また、ロールミルを使用する場合についても、セラミック製ロールを用いることが好ましい。分散装置は、1種のみを使用しても良いし、複数種の装置を組み合わせて使用しても良い。また、強い衝撃で粒子が割れたり、潰れたりしやすい正または負極活物質の場合は、メディア型分散機よりは、ロールミルやホモジナイザー等のメディアレス分散機が好ましい。
(Disperser / Mixer)
As an apparatus used when obtaining the conductive composition of the present invention or a composite ink described later, a disperser or a mixer that is usually used for pigment dispersion or the like can be used.
For example, mixers such as dispersers, homomixers, or planetary mixers; homogenizers such as “Clearmix” manufactured by M Technique, or “fillmix” manufactured by PRIMIX; paint conditioner (manufactured by Red Devil), ball mill, sand mill (Shinmaru Enterprises "Dynomill", etc.), Attritor, Pearl Mill (Eirich "DCP Mill", etc.), or Coball Mill, etc .; Media type dispersers; Wet Jet Mill (Genus, "Genus PY", Sugino Media-less dispersers such as “Starburst” manufactured by Machine, “Nanomizer” manufactured by Nanomizer, etc., “Claire SS-5” manufactured by M Technique, or “MICROS” manufactured by Nara Machinery; or other roll mills, etc. Although The present invention is not limited to these. Moreover, as the disperser, it is preferable to use a disperser that has been subjected to a metal contamination prevention treatment from the disperser.
For example, when using a media-type disperser, a disperser in which the agitator and vessel are made of a ceramic or resin disperser, or the surface of the metal agitator and vessel is treated with tungsten carbide spraying or resin coating. Is preferably used. As the media, it is preferable to use glass beads, ceramic beads such as zirconia beads or alumina beads. Moreover, also when using a roll mill, it is preferable to use a ceramic roll. Only one type of dispersion device may be used, or a plurality of types of devices may be used in combination. Further, in the case of a positive or negative electrode active material in which particles are easily broken or crushed by a strong impact, a medialess disperser such as a roll mill or a homogenizer is preferable to a media type disperser.
本発明の導電性組成物は上記分散機などにより、適切なせん断や衝撃を与えることで導電性組成物を作製することができる。過度のせん断や衝撃を与えると、導電性の炭素材料の二次凝集体が破砕され、通常作動時における電池の内部抵抗上昇や電池内部温度上昇時の内部抵抗が十分に上がらない場合がある。 The conductive composition of the present invention can be produced by applying appropriate shear and impact using the above-described disperser. If excessive shear or impact is applied, the secondary aggregates of the conductive carbon material may be crushed, and the internal resistance of the battery during normal operation or the internal resistance when the battery internal temperature rises may not be sufficiently increased.
導電性組成物におけるカーボンブラックの二次凝集体の大きさは、塗膜の光沢によって評価することができ、二次凝集体が小さくなるに伴い、塗膜の光沢値が大きくなる。導電性組成物をPET(ポリエチレンテレフタレート)フィルムに塗布、乾燥して得られた塗膜を光沢計(60°)によって測定できる。具体的に、導電性組成物の塗膜の光沢値としては0.1〜33であり、好ましくは0.1〜30である。光沢値が高いとカーボンブラックの二次凝集体が小さくなるため、通常作動時における電池の内部抵抗上昇や電池内部温度上昇時の内部抵抗が十分に上がらない場合がある。
本発明において、導電性組成物の塗膜の光沢値は以下のようにして測定することができる。作製した導電性組成物を約1〜5μmとなるように、PET(ポリエチレンテレフタレート)フィルムに塗工したのち、150℃のオーブンに2〜5分入れ、塗膜を作製する。この塗膜を黒色の平板上に置き、光沢計(BYK社製 micro−TRI−gloss)にて測定する。本発明においては、60°の値を読み取り、光沢値とする。
塗膜の光沢の測定においては、PETフィルム上に塗工したものを測定するのが好ましいが、Al箔等に塗工したものを測定しても良い。
The size of the secondary aggregate of carbon black in the conductive composition can be evaluated by the gloss of the coating film, and the gloss value of the coating film increases as the secondary aggregate decreases. The coating film obtained by applying and drying the conductive composition on a PET (polyethylene terephthalate) film can be measured with a gloss meter (60 °). Specifically, the gloss value of the coating film of the conductive composition is 0.1 to 33 , preferably 0.1 to 30. When the gloss value is high, the secondary aggregate of carbon black becomes small, and thus the internal resistance of the battery during normal operation and the internal resistance when the battery internal temperature rises may not be sufficiently increased.
In the present invention, the gloss value of the coating film of the conductive composition can be measured as follows. The prepared conductive composition is applied to a PET (polyethylene terephthalate) film so as to have a thickness of about 1 to 5 μm, and then placed in an oven at 150 ° C. for 2 to 5 minutes to prepare a coating film. This coating film is placed on a black flat plate and measured with a gloss meter (micro-TRI-gloss manufactured by BYK). In the present invention, a value of 60 ° is read as a gloss value.
In measuring the gloss of the coating film, it is preferable to measure what is coated on a PET film, but what is coated on an Al foil or the like may be measured.
(非水電解質二次電池用下地層付き集電体、非水電解質二次電池用電極)
本発明の非水電解質二次電池用下地層付き集電体とは、集電体上に、本発明の導電性組成物から形成された下地層を有するものである。
また、本発明の蓄非水電解質二次電池用電極とは、集電体上に、本発明の導電性組成物から形成された下地層と、電極活物質とバインダーとを含有する電極形成用組成物(合材インキ)から形成された合材層とを有する。
(Current collector with base layer for non-aqueous electrolyte secondary battery, electrode for non-aqueous electrolyte secondary battery)
The current collector with a base layer for a non-aqueous electrolyte secondary battery of the present invention has a base layer formed from the conductive composition of the present invention on the current collector.
In addition, the electrode for a storage nonaqueous electrolyte secondary battery of the present invention is for forming an electrode containing an underlayer formed from the conductive composition of the present invention on a current collector, an electrode active material, and a binder. And a composite material layer formed from the composition (composite ink).
(集電体)
電極に使用する集電体の材質や形状は特に限定されず、各種蓄非水電解質二次電池用にあったものを適宜選択することができる。
例えば、集電体の材質としては、アルミニウム、銅、ニッケル、チタン、又はステンレス等の金属や合金が挙げられる。リチウムイオン電池の場合、特に正極材料としてはアルミニウムが、負極材料としては銅が、それぞれ好ましい。また、形状としては、一般的には平板上の箔が用いられるが、表面を粗面化したものや、穴あき箔状のもの、及びメッシュ状の集電体も使用できる。
(Current collector)
The material and shape of the current collector used for the electrode are not particularly limited, and those suitable for various storage nonaqueous electrolyte secondary batteries can be appropriately selected.
For example, examples of the material for the current collector include metals and alloys such as aluminum, copper, nickel, titanium, and stainless steel. In the case of a lithium ion battery, aluminum is particularly preferable as the positive electrode material, and copper is preferable as the negative electrode material. In general, a flat foil is used as the shape, but a roughened surface, a perforated foil, or a mesh current collector can also be used.
集電体上に導電性組成物や後述する合材インキを塗工する方法としては、特に制限はなく公知の方法を用いることができる。具体的には、ダイコーティング法、ディップコーティング法、ロールコーティング法、ドクターコーティング法、ナイフコーティング法、スプレーコティング法、グラビアコーティング法、スクリーン印刷法または静電塗装法等が挙げる事ができ、乾燥方法としては放置乾燥、送風乾燥機、温風乾燥機、赤外線加熱機、遠赤外線加熱機などが使用できるが、特にこれらに限定されるものではなく、塗布後に平版プレスやカレンダーロール等による圧延処理を行っても良い。 There is no restriction | limiting in particular as a method of apply | coating a conductive composition and the mixture ink mentioned later on a collector, A well-known method can be used. Specific examples include die coating method, dip coating method, roll coating method, doctor coating method, knife coating method, spray coating method, gravure coating method, screen printing method or electrostatic coating method, and the like. Examples of methods that can be used include standing drying, blow dryers, hot air dryers, infrared heaters, and far infrared heaters, but are not limited to these, and rolling treatment with a lithographic press or calender roll after application. May be performed.
下地層の厚みは、好ましくは0.1〜10μmであり、より好ましくは0.5〜5μm、さらに好ましくは0.5〜3μmである。下地層の厚みが薄すぎると、集電体と活物質とが直接接触するバイパス部分が局所的に形成され、電池が発熱した際、下地層部分の抵抗増大による電流遮断効果が不十分となる。一方、下地層の厚みが厚すぎると、電極に占める下地層の割合が増大し、活物質の含有比率が低下し、電池の容量が低下する。 The thickness of the underlayer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm, and still more preferably 0.5 to 3 μm. If the thickness of the underlayer is too thin, a bypass portion where the current collector and the active material are in direct contact is locally formed, and when the battery generates heat, the current blocking effect due to the increase in resistance of the underlayer portion becomes insufficient. . On the other hand, if the thickness of the underlayer is too thick, the proportion of the underlayer in the electrode increases, the active material content ratio decreases, and the battery capacity decreases.
下地層は集電体の片面もしくは両面に設置できるが、熱による抵抗上昇や電池の内部抵抗低減の観点から、集電体の両面に設置することが好ましい。 The underlayer can be provided on one side or both sides of the current collector, but it is preferably provided on both sides of the current collector from the viewpoint of increasing resistance due to heat and reducing the internal resistance of the battery.
<合材インキ>
前記したように、一般的な蓄電デバイス用の合材インキは、活物質と、溶媒を必須とし、必要に応じて導電助剤と、バインダーとを含有する。
活物質はできるだけ多く含まれることが好ましく、例えば、合材インキ固形分に占める活物質の割合は、80〜99質量%が好ましい。導電助剤を含む場合、合材インキ固形分に占める導電助剤の割合は、0.1〜15質量%であることが好ましい。バインダーを含む場合、合材インキ固形分に占めるバインダーの割合は、0.1〜15質量%であることが好ましい。
<Composite ink>
As described above, a general ink mixture for a power storage device essentially includes an active material and a solvent, and contains a conductive additive and a binder as necessary.
The active material is preferably contained as much as possible. For example, the proportion of the active material in the solid material ink solid content is preferably 80 to 99 % by mass. When the conductive assistant is included, the proportion of the conductive assistant in the solid ink solid content is preferably 0.1 to 15% by mass. When the binder is included, the ratio of the binder to the solid material ink solid content is preferably 0.1 to 15% by mass.
塗工方法によるが、固形分30〜90質量%の範囲で、合材インキの粘度は、100mPa・s以上、30,000mPa・s以下とするのが好ましい。 Although it depends on the coating method, the viscosity of the composite ink is preferably 100 mPa · s or more and 30,000 mPa · s or less in the range of 30 to 90% by mass of the solid content.
(活物質)
合材インキ中で使用される活物質について以下で説明する。
リチウムイオン二次電池用の正極活物質としては、特に限定はされないが、リチウムイオンをドーピングまたはインターカレーション可能な金属酸化物、金属硫化物等の金属化合物、および導電性高分子等を使用することができる。
(Active material)
The active material used in the composite ink will be described below.
The positive electrode active material for the lithium ion secondary battery is not particularly limited, but metal oxides capable of doping or intercalating lithium ions, metal compounds such as metal sulfides, and conductive polymers are used. be able to.
例えば、Fe、Co、Ni、Mn等の遷移金属の酸化物、リチウムとの複合酸化物、遷移金属硫化物等の無機化合物等が挙げられる。具体的には、MnO、V2O5、V6O13、
TiO2等の遷移金属酸化物粉末、層状構造のニッケル酸リチウム、コバルト酸リチウム
、マンガン酸リチウム、スピネル構造のマンガン酸リチウムなどのリチウムと遷移金属との複合酸化物粉末、オリビン構造のリン酸化合物であるリン酸鉄リチウム系材料、TiS2、FeSなどの遷移金属硫化物粉末等が挙げられる。
Examples thereof include transition metal oxides such as Fe, Co, Ni, and Mn, composite oxides with lithium, and inorganic compounds such as transition metal sulfides. Specifically, MnO, V 2 O 5 , V 6 O 13 ,
Transition metal oxide powders such as TiO 2, lithium nickelate with layered structure, lithium cobaltate, lithium manganate, composite oxide powder of lithium and transition metal such as spinel structure lithium manganate, phosphate compound with olivine structure Examples thereof include lithium iron phosphate materials, transition metal sulfide powders such as TiS 2 and FeS.
また、ポリアニリン、ポリアセチレン、ポリピロール、ポリチオフェン等の導電性高分子を使用することもできる。また、上記の無機化合物や導電性高分子を混合して用いてもよい。 In addition, conductive polymers such as polyaniline, polyacetylene, polypyrrole, and polythiophene can also be used. Moreover, you may mix and use said inorganic compound and conductive polymer.
リチウムイオン二次電池用の負極活物質としては、リチウムイオンをドーピングまたはインターカレーション可能なものであれば特に限定されない。例えば、金属Li、その合金であるスズ合金、シリコン合金、鉛合金等の合金系、LiXFe2O3、LiXFe3O4、LiXWO2、チタン酸リチウム、バナジウム酸リチウム、ケイ素酸リチウム等の金属酸化物系、ポリアセチレン、ポリ−p−フェニレン等の導電性高分子系、ソフトカーボンやハードカーボンといった、アモルファス系炭素質材料や、高黒鉛化炭素材料等の人造黒鉛、あるいは天然黒鉛等の炭素質粉末、カーボンブラック、メソフェーズカーボンブラック、樹脂焼成炭素材料、気層成長炭素繊維、炭素繊維などの炭素系材料が挙げられる。これら負極活物質は、1種または複数を組み合わせて使用することも出来る。 The negative electrode active material for the lithium ion secondary battery is not particularly limited as long as it can be doped or intercalated with lithium ions. For example, metal Li, alloys thereof such as tin alloys, silicon alloys, lead alloys, Li x Fe 2 O 3 , Li x Fe 3 O 4 , Li x WO 2 , lithium titanate, lithium vanadate, silicon Metal oxides such as lithium oxide, conductive polymers such as polyacetylene and poly-p-phenylene, amorphous carbonaceous materials such as soft carbon and hard carbon, artificial graphite such as highly graphitized carbon materials, or natural Examples thereof include carbonaceous powders such as graphite, carbon black, mesophase carbon black, resin-fired carbon materials, air-growth carbon fibers, and carbon fibers. These negative electrode active materials can be used alone or in combination.
合材インキ中の導電助剤とは、導電性を有する炭素材料であれば特に限定されるものではなく、上述の導電性の炭素材料(A)と同様のものも使用できる。 The conductive assistant in the composite ink is not particularly limited as long as it is a carbon material having conductivity, and the same conductive carbon material (A) as described above can be used.
合材インキ中のバインダーとは、活物質や導電性の炭素材料などの粒子同士、あるいは導電性の炭素材料と集電体を結着させるために使用されるものである。 The binder in the composite ink is used for binding particles such as an active material or a conductive carbon material, or a conductive carbon material and a current collector.
合材インキ中で使用されるバインダーとしては、例えば、アクリル樹脂、ポリウレタン樹脂、ポリエステル樹脂、フェノール樹脂、エポキシ樹脂、フェノキシ樹脂、尿素樹脂、メラミン樹脂、アルキッド樹脂、ホルムアルデヒド樹脂、シリコン樹脂、フッ素樹脂、カルボキシメチルセルロース等のセルロース樹脂、スチレン−ブタジエンゴムやフッ素ゴム等の合成ゴム、ポリアニリンやポリアセチレン等の導電性樹脂等、ポリフッ化ビニリデン、ポリフッ化ビニル、及びテトラフルオロエチレン等のフッ素原子を含む高分子化合物が挙げられる。また、これらの樹脂の変性物、混合物、又は共重合体でも良い。これらバインダーは、1種または複数を組み合わせて使用することも出来る。
また、水性の合材インキ中で好適に使用されるバインダーとしては水媒体のものが好ましく、水媒体のバインダーの形態としては、水溶性型、エマルション型、ハイドロゾル型等が挙げられ、適宜選択することができる。
Examples of binders used in the composite ink include acrylic resin, polyurethane resin, polyester resin, phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, formaldehyde resin, silicon resin, fluorine resin, Cellulose resins such as carboxymethyl cellulose, synthetic rubbers such as styrene-butadiene rubber and fluororubber, conductive resins such as polyaniline and polyacetylene, and polymer compounds containing fluorine atoms such as polyvinylidene fluoride, polyvinyl fluoride, and tetrafluoroethylene Is mentioned. Further, a modified product, a mixture, or a copolymer of these resins may be used. These binders can be used alone or in combination.
The binder suitably used in the water-based composite ink is preferably an aqueous medium, and examples of the aqueous medium binder include water-soluble type, emulsion type, hydrosol type, and the like. be able to.
さらに、合材インキには、成膜助剤、消泡剤、レベリング剤、防腐剤、pH調整剤、粘性調整剤などを必要に応じて配合できる。 Furthermore, a film forming aid, an antifoaming agent, a leveling agent, a preservative, a pH adjuster, a viscosity adjuster, and the like can be blended in the composite ink as necessary.
<電極の製造方法>
本発明の導電性組成物を、集電体上に塗工・乾燥し、下地層を形成し、非水電解質二次電池用下地層電極を得ることができる。
あるいは、本発明の導電性組成物を、集電体上に塗工・乾燥し、下地層を形成し、該下地層上に、合材層を設け、非水電解質二次電池用電極を得ることもできる。下地層上に設ける合材層は、上記した合材インキを用いて形成することができる。
<Method for producing electrode>
The conductive composition of the present invention can be applied and dried on a current collector to form a base layer, whereby a base layer electrode for a nonaqueous electrolyte secondary battery can be obtained.
Alternatively, the conductive composition of the present invention is coated and dried on a current collector to form a base layer, and a composite layer is provided on the base layer to obtain an electrode for a nonaqueous electrolyte secondary battery. You can also The composite material layer provided on the base layer can be formed using the above-described composite ink.
(電解液)
リチウムイオン二次電池の場合を例にとって説明する。電解液としては、リチウムを含んだ電解質を非水系の溶剤に溶解したものを用いる。
電解質としては、LiBF4、LiClO4、LiPF6、LiAsF6、LiSbF6、LiCF3SO3、Li(CF3SO2)2N、LiC4F9SO3、Li(CF3SO2)3C、LiI、LiBr、LiCl、LiAlCl、LiHF2、LiSCN、又はLiBPh4等が挙げられるがこれらに限定されない。
(Electrolyte)
A case of a lithium ion secondary battery will be described as an example. As the electrolytic solution, an electrolyte containing lithium dissolved in a non-aqueous solvent is used.
As electrolytes, LiBF 4 , LiClO 4 , LiPF 6 , LiAsF 6 , LiSbF 6 , LiCF 3 SO 3 , Li (CF 3 SO 2 ) 2 N, LiC 4 F 9 SO 3 , Li (CF 3 SO 2 ) 3 C , LiI, LiBr, LiCl, LiAlCl, LiHF 2 , LiSCN, or LiBPh 4, but are not limited thereto.
非水系の溶剤としては特に限定はされないが、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、ジメチルカーボネート、エチルメチルカーボネート、及びジエチルカーボネート等のカーボネート類;
γ−ブチロラクトン、γ−バレロラクトン、及びγ−オクタノイックラクトン等のラクトン類;
テトラヒドロフラン、2−メチルテトラヒドロフラン、1,3−ジオキソラン、4−メチル−1,3−ジオキソラン、1,2−メトキシエタン、1,2−エトキシエタン、及び1,2−ジブトキシエタン等のグライム類;
メチルフォルメート、メチルアセテート、及びメチルプロピオネート等のエステル類;ジメチルスルホキシド、及びスルホラン等のスルホキシド類;並びに、
アセトニトリル等のニトリル類等が挙げられる。又これらの溶剤は、それぞれ単独で使用しても良いが、2種以上を混合して使用しても良い。
さらに上記電解液を、ポリマーマトリクスに保持しゲル状とした高分子電解質とすることもできる。ポリマーマトリクスとしては、ポリアルキレンオキシドセグメントを有するアクリレート系樹脂、ポリアルキレンオキシドセグメントを有するポリホスファゼン系樹脂、及びポリアルキレンオキシドセグメントを有するポリシロキサン等が挙げられるがこれらに限定されない。
Although it does not specifically limit as a non-aqueous solvent, For example, carbonates, such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate;
Lactones such as γ-butyrolactone, γ-valerolactone, and γ-octanoic lactone;
Glymes such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2-dibutoxyethane;
Esters such as methyl formate, methyl acetate, and methyl propionate; sulfoxides such as dimethyl sulfoxide and sulfolane; and
Nitriles such as acetonitrile are exemplified. These solvents may be used alone or in combination of two or more.
Furthermore, the electrolyte solution may be a polymer electrolyte that is held in a polymer matrix and made into a gel. Examples of the polymer matrix include, but are not limited to, an acrylate resin having a polyalkylene oxide segment, a polyphosphazene resin having a polyalkylene oxide segment, and a polysiloxane having a polyalkylene oxide segment.
(セパレーター)
セパレーターとしては、例えば、ポリエチレン不織布、ポリプロピレン不織布、ポリアミド不織布及びそれらに親水性処理を施したものが挙げられるが、特にこれらに限定されるものではない。
(separator)
Examples of the separator include, but are not limited to, a polyethylene nonwoven fabric, a polypropylene nonwoven fabric, a polyamide nonwoven fabric and those obtained by subjecting them to a hydrophilic treatment.
(実施例1)
<導電性組成物>
導電性の炭素材料としてアセチレンブラック(A−1:デンカブラックHS−100、電気化学工業社製)25質量部、水溶性樹脂であるカルボキシメチルセルロース(CMCダイセル#1240、ダイセル化学工業社製)2.5%水溶液1000質量部(固形分として25質量部)をミキサーに入れて混合し、更にサンドミルに入れて分散を行った。次に水分散樹脂粒子であるポリオレフィン系樹脂微粒子(C−1:アローベースSB−1200、ユニチカ社製、25%水系分散液(平均粒子径0.10μm))200質量部(固形分として50質量部)を入れ、ミキサーで混合し、導電性組成物(1)を得た。
Example 1
<Conductive composition>
1. 25 parts by mass of acetylene black (A-1: Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive carbon material, carboxymethyl cellulose which is a water-soluble resin (CMC Daicel # 1240, manufactured by Daicel Kagaku Kogyo Co., Ltd.) 1000 parts by mass of a 5% aqueous solution (25 parts by mass as a solid content) was mixed in a mixer, and further dispersed in a sand mill. Next, polyolefin resin fine particles (C-1: Arrow Base SB-1200, manufactured by Unitika Co., Ltd., 25% aqueous dispersion (average particle size: 0.10 μm)) as water-dispersed resin particles, 200 parts by mass (50 mass as solid content) Part) and mixed with a mixer to obtain a conductive composition (1).
実施例および比較例に用いた材料および塗膜の評価については、以下の通り行った。
(光沢値)
作製した導電性組成物を約1〜5μmとなるように、PET(ポリエチレンテレフタレート)フィルムに塗工した後、150℃のオーブンに2〜5分入れ、塗膜を作製した。この塗膜を黒色の平板上に置き、光沢計(BYK社製 micro−TRI−gloss)にて60°の値を読み取った。
(導電性炭素材料の一次粒子径)
透過型電子顕微鏡(日本電子データム社製 JEM−1010)を用いて、加速電圧100kVにて炭素材料粒子の撮影を行った。アグリゲート(一次凝集体)を形成する球形粒子100個の直径を測長し、平均化して求めた。
(導電性炭素材料の体積平均粒子径)
導電性の炭素材料(A)と水溶性樹脂(B)を機械分散したスラリーを、固形分に応じて100〜1000倍に水希釈し、マイクロトラック(日機装社製 MT3300EXII)のセルに該希釈スラリーをサンプリングローディングにおいて適正濃度になるまで注入し、サンプルに応じた分散媒(本発明では水)の屈折率条件を入力後、測定を行い、D50を平均粒子径とした。
(水分散樹脂微粒子の体積平均粒子径)
水分散樹脂微粒子分散液を、固形分に応じて200〜1000倍に水希釈し。該希釈液約5mlをナノトラック(日機装社製 Wave−EX150)のセルに注入し、サンプルに応じた分散媒(本発明では水)および樹脂の屈折率条件を入力後、測定を行い、D50を平均粒子径とした。
(オレフィン系樹脂微粒子の変性量(Y)/(X))
水分散樹脂微粒子(C)を80℃のオーブンに入れ、分散媒を除去した後、120℃で30分乾燥させて固形物を得た。これをフーリエ変換赤外分光装置(FT−IR:PerkinElmer社製Spectrum One/100)による全反射測定法(ATR)によって測定した。
変性量は、波数に対して吸光度をプロットしたスペクトルを用い、2700cm-1における吸光度を示す点と3000cm-1における吸光度を示す点との2点を結ぶ直線をベースラインBXとした際の、2800〜3000cm-1のオレフィン由来の最大ピークからベースラインBXまでの高さ(極大吸光度)(X)と、1650m-1における吸光度を示す点と1850cm-1における吸光度を示す点との2点を結ぶ直線をベースラインBYとした際の、1690〜1740cm-1のカルボニル由来の最大ピークからベースラインBYまでの高さ(極大吸光度)(Y)との比(Y)/(X)を求めた。
The materials and coating films used in the examples and comparative examples were evaluated as follows.
(Gloss value)
The prepared conductive composition was applied to a PET (polyethylene terephthalate) film so as to have a thickness of about 1 to 5 μm, and then placed in an oven at 150 ° C. for 2 to 5 minutes to prepare a coating film. This coating film was placed on a black flat plate, and a value of 60 ° was read with a gloss meter (micro-TRI-gloss manufactured by BYK).
(Primary particle size of conductive carbon material)
The carbon material particles were photographed at an acceleration voltage of 100 kV using a transmission electron microscope (JEM-1010 manufactured by JEOL Datum). The diameters of 100 spherical particles forming an aggregate (primary aggregate) were measured and averaged.
(Volume average particle diameter of conductive carbon material)
A slurry obtained by mechanically dispersing a conductive carbon material (A) and a water-soluble resin (B) is diluted with water 100 to 1000 times depending on the solid content, and the diluted slurry is placed in a cell of Microtrac (MT3300EXII manufactured by Nikkiso Co., Ltd.). Was sampled until the appropriate concentration was obtained in sampling loading, and after inputting the refractive index condition of the dispersion medium (water in the present invention) according to the sample, measurement was performed, and D50 was defined as the average particle size.
(Volume average particle diameter of water-dispersed resin fine particles)
The water-dispersed resin fine particle dispersion is diluted with water 200 to 1000 times depending on the solid content. About 5 ml of the diluted solution is injected into a cell of Nanotrac (Wave-EX150 manufactured by Nikkiso Co., Ltd.), and after inputting the refractive index conditions of the dispersion medium (water in the present invention) and the resin according to the sample, measurement is performed, and D50 is The average particle size was taken.
(Modification amount of olefin resin fine particles (Y) / (X))
The water-dispersed resin fine particles (C) were placed in an oven at 80 ° C. to remove the dispersion medium, and then dried at 120 ° C. for 30 minutes to obtain a solid. This was measured by a total reflection measurement method (ATR) using a Fourier transform infrared spectrometer (FT-IR: Spectrum One / 100 manufactured by PerkinElmer).
Modification amount using spectral plotting absorbance against wave numbers, when used as a baseline BX a straight line connecting two points of the point indicating the absorbance at a point and 3000 cm -1 indicating the absorbance at 2700 cm -1, 2800 The height (maximum absorbance) (X) from the maximum peak derived from the olefin of ˜3000 cm −1 to the baseline BX is connected to the point indicating the absorbance at 1650 m −1 and the point indicating the absorbance at 1850 cm −1 . The ratio (Y) / (X) to the height (maximum absorbance) (Y) from the maximum peak derived from the carbonyl of 1690 to 1740 cm −1 to the baseline BY when the straight line was taken as the baseline BY was determined.
(実施例2〜実施例47)
表1に示す組成比、および導電性の炭素材料と水溶性樹脂のサンドミルでの分散時間を延長して導電性材料の光沢値を変更した以外は、導電性組成物(1)と同様の方法により、それぞれ実施例の導電性組成物(2)〜(8)、(12)〜(16)、(18)〜(20)、(25)〜(51)を得た。なお、実施例45、46は参考例である。
(Example 2 to Example 47)
The same method as the conductive composition (1) except that the composition ratio shown in Table 1 and the gloss time of the conductive material were changed by extending the dispersion time of the conductive carbon material and the water-soluble resin in the sand mill. Thus, conductive compositions (2) to (8), (12) to (16), (18) to (20), and (25) to (51) of Examples were obtained, respectively. Examples 45 and 46 are reference examples.
実施例および比較例で使用した材料を以下に示す。
(導電性の炭素材料(A))
・A−1:デンカブラックHS−100(電気化学工業社製)
・A−2:ケッチェンブラックEC−300J(ライオン社製)
(水溶性樹脂)(B))
・B−1:CMCダイセル#1240(ダイセル化学工業社製)
・B−2:ポリアクリル酸、平均分子量5000(和光純薬工業社製)
・B−3:クラレポバールPVA235(クラレ社製)
・B−4:CMCダイセル#1110(ダイセル化学工業社製)
・B−5:CMCダイセル#1120(ダイセル化学工業社製)
・B−6:CMCダイセル#1130(ダイセル化学工業社製)
・B−7:CMCダイセル#1140(ダイセル化学工業社製)
・B−8:CMCダイセル#1260(ダイセル化学工業社製)
(水分散樹脂粒子(C))
・C−1:アローベースSB−1200(固形分25%水分散液、平均粒子径0.10μm)(ユニチカ社製)
・C−2:アローベースTC−4010(固形分25%水分散液、平均粒子径0.20μm)(ユニチカ社製)
・C−3:アクアペトロDP−2401(固形分30%水分散液、平均粒子径0.30μm)(東洋アドレ社製)
・C−4:ポリテトラフルオロエチレン30−J(固形分60%水分散液、平均粒子径0.2μm)(三井・デュポンフロロケミカル社製)
・C−6:ザイクセンAC(固形分30%水分散液、平均粒子径0.04μm)(住友精化社製)
・C−7:アローベースSE−1200(固形分20%水分散液、平均粒子径0.12μm)(ユニチカ社製)
・C−8:ハイテックS−3121(固液分25%水分散液、平均粒子径0.01μm)(東邦化学社製)
・C−9:ケミパールV300(固形分40%水分散液、平均粒子径3.50μm)(三井化学社製)
・C−10:ケミパールS100(固形分28%水分散液、平均粒子径0.02μm)(三井化学社製)
・C−11:ケミパールW4005(固形分40%水分散液、平均粒子径0.57μm)(三井化学社製)
・C−12:アローベースTD−4010(固形分25%水分散液、平均粒子径0.17μm)(ユニチカ社製)
・C−13:ハードレンNZ−1015(固形分30%水分散液、平均粒子径0.15μm)(東洋紡社製)
・C−14:ハードレンNZ−1004(固形分30%水分散液、平均粒子径0.12μm)(東洋紡社製)
The materials used in Examples and Comparative Examples are shown below.
(Conductive carbon material (A))
A-1: Denka Black HS-100 (manufactured by Denki Kagaku Kogyo)
A-2: Ketjen Black EC-300J (Lion Corporation)
(Water-soluble resin) (B))
B-1: CMC Daicel # 1240 (manufactured by Daicel Chemical Industries)
B-2: polyacrylic acid, average molecular weight 5000 (manufactured by Wako Pure Chemical Industries, Ltd.)
B-3: Kuraray Poval PVA235 (manufactured by Kuraray)
B-4: CMC Daicel # 1110 (manufactured by Daicel Chemical Industries)
B-5: CMC Daicel # 1120 (manufactured by Daicel Chemical Industries)
B-6: CMC Daicel # 1130 (manufactured by Daicel Chemical Industries)
B-7: CMC Daicel # 1140 (manufactured by Daicel Chemical Industries)
B-8: CMC Daicel # 1260 (manufactured by Daicel Chemical Industries)
(Water-dispersed resin particles (C))
C-1: Arrow Base SB-1200 (25% solid content aqueous dispersion, average particle size 0.10 μm) (manufactured by Unitika)
C-2: Arrow base TC-4010 (25% solid content aqueous dispersion, average particle size 0.20 μm) (manufactured by Unitika)
C-3: Aqua Petro DP-2401 (solid content 30% aqueous dispersion, average particle size 0.30 μm) (manufactured by Toyo Adre)
C-4: polytetrafluoroethylene 30-J (solid dispersion 60% aqueous dispersion, average particle size 0.2 μm) (Mitsui / DuPont Fluorochemicals)
C-6: Saixen AC (solid content 30% aqueous dispersion, average particle size 0.04 μm) (manufactured by Sumitomo Seika Co., Ltd.)
C-7: Arrow Base SE-1200 (20% solid content aqueous dispersion, average particle size 0.12 μm) (manufactured by Unitika)
C-8: Hitech S-3121 (25% solid-liquid dispersion, average particle size 0.01 μm) (manufactured by Toho Chemical Co., Ltd.)
C-9: Chemipearl V300 (40% solid content aqueous dispersion, average particle size 3.50 μm) (Mitsui Chemicals)
C-10: Chemipearl S100 (28% solid content aqueous dispersion, average particle size 0.02 μm) (Mitsui Chemicals)
C-11: Chemipearl W4005 (40% solid content aqueous dispersion, average particle size 0.57 μm) (Mitsui Chemicals)
C-12: Arrow Base TD-4010 (25% solid content aqueous dispersion, average particle size 0.17 μm) (manufactured by Unitika)
C-13: Hardren NZ-1015 (solid content 30% aqueous dispersion, average particle size 0.15 μm) (manufactured by Toyobo Co., Ltd.)
C-14: Hardren NZ-1004 (30% solid content aqueous dispersion, average particle size 0.12 μm) (manufactured by Toyobo Co., Ltd.)
(比較例2)
水分散樹脂微粒子をスチレンブタジエンエマルション(C−5:TRD2001(固形分48%水分散液)、JSR社製)に代えた以外は、実施例1と同様の方法により、導電性組成物(22)を得た。
(Comparative Example 2)
A conductive composition (22) was produced in the same manner as in Example 1 except that the water-dispersed resin fine particles were replaced with a styrene-butadiene emulsion (C-5: TRD2001 (solid dispersion 48% aqueous dispersion), manufactured by JSR Corporation). Got.
(比較例3)
導電性の炭素材料としてアセチレンブラック(A−1:デンカブラックHS−100、電気化学工業社)30質量部、非水溶性樹脂であるポリフッ化ビニリデン(KFポリマー#9100::クレハ社)35質量部とN―メチルピロリドン900質量部をミキサーに入れて混合した後、融点が130℃、密度が0.98g/mlの固形のポリオレフィン樹脂35質量部入れ、160℃のオーブンに入れてポリオレフィン樹脂を溶解させた後、サンドミルに入れて分散を行い、導電性組成物(23)を得た。
(Comparative Example 3)
30 parts by mass of acetylene black (A-1: Denka Black HS-100, Denki Kagaku Kogyo Co., Ltd.) as a conductive carbon material, 35 parts by mass of polyvinylidene fluoride (KF polymer # 9100 :: Kureha Co.) which is a water-insoluble resin And 900 parts by mass of N-methylpyrrolidone in a mixer, and after mixing, 35 parts by mass of a solid polyolefin resin having a melting point of 130 ° C. and a density of 0.98 g / ml is placed in an oven at 160 ° C. to dissolve the polyolefin resin. Then, the mixture was placed in a sand mill and dispersed to obtain a conductive composition (23).
(比較例4)
導電性の炭素材料としてアセチレンブラック(A−1:デンカブラックHS−100、電気化学工業社)28質量部、非水溶性樹脂であるポリフッ化ビニリデン(KFポリマー#9100:クレハ社)72質量部とN―メチルピロリドン900質量部をミキサーに入れて混合し、更にサンドミルに入れて分散を行い、導電性組成物(24)を得た。
(Comparative Example 4)
28 parts by mass of acetylene black (A-1: Denka Black HS-100, Denki Kagaku Kogyo Co., Ltd.) as a conductive carbon material, 72 parts by mass of polyvinylidene fluoride (KF polymer # 9100: Kureha Co.) which is a water-insoluble resin, 900 parts by mass of N-methylpyrrolidone was mixed in a mixer, and further dispersed in a sand mill to obtain a conductive composition (24).
<下地層付き集電体>(実施例1〜19、21〜47、比較例2、3)
導電性組成物(1)〜(19)、(25)〜(51)、(22)〜(23)を、集電体となる厚さ20μmのアルミ箔上にバーコーターを用いて塗布をした後、80℃で加熱乾燥し、表1に示す厚み(比較例3は厚み2μm)となるように非水電解質二次電池用下地層付き集電体(1)〜(19)、(25)〜(51)、(22)〜(23)をそれぞれ得た。
<Current Collector with Underlayer> (Examples 1 to 19, 21 to 47, Comparative Examples 2 and 3)
Conductive compositions (1) to (19), (25) to (51), and (22) to (23) were coated on a 20 μm thick aluminum foil serving as a current collector using a bar coater. Then, it heat-dried at 80 degreeC, and the collector (1)-(19), (25) with a base layer for nonaqueous electrolyte secondary batteries so that it may become thickness shown in Table 1 (comparative example 3 is 2 micrometers in thickness). To (51) and (22) to (23) were obtained.
<下地層付き集電体>(実施例20)
導電性組成物(20)を、集電体となる厚さ20μmの銅箔上にバーコーターを用いて塗布をした後、80℃で加熱乾燥し、厚みが2μmとなるように非水電解質二次電池用下地層付き集電体(20)を得た。
<Current Collector with Underlayer> (Example 20)
The conductive composition (20) was applied on a copper foil having a thickness of 20 μm serving as a current collector using a bar coater, and then dried by heating at 80 ° C. so that the thickness became 2 μm. A current collector (20) with a base layer for a secondary battery was obtained.
<下地層付き集電体>(比較例4)
導電性組成物(24)を、集電体となる厚さ20μmのアルミ箔上にバーコーターを用いて厚みが2μmとなるように塗布をした後、80℃で加熱乾燥を行った。次いで、145℃のオーブンに入れて5時間の熱処理を行って、非水電解質二次電池用下地層付き集電体(24)を得た。
<Current collector with underlayer> (Comparative Example 4)
The conductive composition (24) was applied on a 20 μm-thick aluminum foil serving as a current collector to a thickness of 2 μm using a bar coater, and then heat-dried at 80 ° C. Subsequently, it heat-processed for 5 hours in 145 degreeC oven, and obtained the collector (24) with the base layer for nonaqueous electrolyte secondary batteries.
<リチウムイオン二次電池正極用合材インキ>
正極活物質としてLiNi0.5Mn0.3Co0.2O293質量部、導電剤としてアセチレンブラック4質量部、バインダーとしてポリフッ化ビニリデン3質量部、N―メチルピロリドン45質量部を入れて混合して、正極用合材インキを作製した。
<Composite ink for lithium ion secondary battery positive electrode>
93 parts by mass of LiNi 0.5 Mn 0.3 Co 0.2 O 2 as a positive electrode active material, 4 parts by mass of acetylene black as a conductive agent, 3 parts by mass of polyvinylidene fluoride as a binder, and 45 parts by mass of N-methylpyrrolidone are mixed and mixed. A composite ink was prepared.
<リチウムイオン二次電池負極用合材インキ>
負極活物質として人造黒鉛98質量部、カルボキシメチルセルロース1.5%水溶液66.7質量部(固形分として1質量部)をプラネタリーミキサーに入れて混練し、水33質量部、スチレンブタジエンエマルション48質量%水系分散液2.08質量部(固形分として1質量部)を混合して、負極二次電池電極用合材インキを得た。
<Composite ink for negative electrode of lithium ion secondary battery>
As a negative electrode active material, 98 parts by mass of artificial graphite and 66.7 parts by mass of a carboxymethyl cellulose 1.5% aqueous solution (1 part by mass as a solid content) were put in a planetary mixer and kneaded, 33 parts by mass of water, 48 parts by mass of a styrene butadiene emulsion. 2.08 parts by mass of a 1% aqueous dispersion (1 part by mass as a solid content) was mixed to obtain a mixture ink for negative electrode secondary battery electrode.
<下地層付きリチウムイオン二次電池用正極>(実施例1〜19、21〜47、比較例2〜4)
上述のリチウムイオン二次電池正極用合材インキを、二次電池用下地層付き集電体(1)〜(19)、(25)〜(51)、(22)〜(24)上にドクターブレードを用いて塗布した後、80℃で加熱乾燥して電極の単位面積当たりの目付け量が20mg/cm2となるようにとなるように調整した。さらにロールプレスによる圧延処理を行い、合材層の密度が3.1g/cm3となる正極(1)〜(19)、(25)〜(51)、(22)〜(24)を作製した。
<Positive Electrode for Lithium Ion Secondary Battery with Underlayer> (Examples 1 to 19, 21 to 47, Comparative Examples 2 to 4)
The above lithium-ion secondary battery positive electrode mixture ink is applied to the secondary battery undercoat current collectors (1) to (19), (25) to (51), and (22) to (24) on the doctor. After coating using a blade, the coating was adjusted by heating and drying at 80 ° C. so that the basis weight per unit area of the electrode was 20 mg / cm 2 . Furthermore, the rolling process by a roll press was performed and the positive electrode (1)-(19), (25)-(51), (22)-(24) from which the density of a compound-material layer became 3.1 g / cm < 3 > was produced. .
<下地層なしリチウムイオン二次電池用正極>(実施例20、比較例1用正極)
上述のリチウムイオン二次電池正極用合材インキを、集電体となる厚さ20μmのアルミ箔上にドクターブレードを用いて塗布した後、80℃で加熱乾燥して電極の単位面積当たりの目付け量が20mg/cm2となるようにとなるように調整した。さらにロールプレスによる圧延処理を行い、合材層の密度が3.1g/cm3となる正極(20)、(21)を作製した。
<Positive electrode for lithium ion secondary battery without base layer> (Example 20, positive electrode for Comparative Example 1)
After applying the above-mentioned ink mixture for lithium ion secondary battery positive electrode on a 20 μm-thick aluminum foil serving as a current collector using a doctor blade, it is dried by heating at 80 ° C., and the basis weight per unit area of the electrode The amount was adjusted to 20 mg / cm 2 . Furthermore, the rolling process by a roll press was performed and the positive electrodes (20) and (21) from which the density of a compound-material layer became 3.1 g / cm < 3 > were produced.
<下地層なしリチウムイオン二次電池用負極>(実施例1〜19、21〜47、比較例1〜4用負極)
上述のリチウムイオン二次電池負極用合材インキを、集電体となる厚さ20μmの銅箔上にドクターブレードを用いて塗布した後、80℃で加熱乾燥して電極の単位面積当たりの目付け量が12mg/cm2となるように調整した。さらにロールプレスによる圧延処理を行い、合材層の密度が1.5g/cm3となる負極(1)〜(19)、(25)〜(51)、(21)〜(24)を作製した。
<Negative Electrode for Lithium Ion Secondary Battery> (Negative Examples 1-19, 21-47, Comparative Examples 1-4)
After applying the above-mentioned ink mixture for lithium ion secondary battery negative electrode on a copper foil having a thickness of 20 μm as a current collector using a doctor blade, it is dried by heating at 80 ° C. per unit area of the electrode The amount was adjusted to 12 mg / cm 2 . Furthermore, the rolling process by roll press was performed and the negative electrode (1)-(19), (25)-(51), (21)-(24) from which the density of a compound-material layer was set to 1.5 g / cm < 3 > was produced. .
<下地層付きリチウムイオン二次電池用負極>(実施例20)
上述のリチウムイオン二次電池負極用合材インキを、下地層付き集電体(20)上にドクターブレードを用いて塗布した後、80℃で加熱乾燥して電極の単位面積当たりの目付け量が12mg/cm2となるように調整した。さらにロールプレスによる圧延処理を行い、合材層の密度が1.5g/cm3となる負極(20)を作製した。
<Anode for Lithium Ion Secondary Battery with Underlayer> (Example 20)
After applying the above mixture ink for a negative electrode of a lithium ion secondary battery on the current collector (20) with the underlayer using a doctor blade, it is heated and dried at 80 ° C. so that the basis weight per unit area of the electrode is It adjusted so that it might become 12 mg / cm < 2 >. Furthermore, the rolling process by a roll press was performed and the negative electrode (20) from which the density of a compound-material layer became 1.5 g / cm < 3 > was produced.
<ラミネート型リチウムイオン二次電池>(実施例1〜47、比較例1〜4)
表2に示す正極と負極を各々45mm×40mm、50mm×45mmに打ち抜き、その間に挿入されるセパレーター(多孔質ポリプロプレンフィルム)とをアルミ製ラミネート袋に挿入し、真空乾燥の後、電解液(エチレンカーボネートとジエチルカーボネートを1:1(体積比)の割合で混合した混合溶媒に、LiPF6を1Mの濃度で溶解させた非水系電解液)を注入した後、アルミ製ラミネートを封口してラミネート型リチウムイオン電池を作製した。ラミネート型リチウムイオン型電池の作製はアルゴンガス置換したグロ−ブボックス内で行い、ラミネート型リチウムイオン型電池作製後、以下に示す初期抵抗、抵抗増加、レート特性およびサイクル特性の電池特性評価を行った。なお、実施例45、46は参考例である。
<Laminated Lithium Ion Secondary Battery> (Examples 1 to 47, Comparative Examples 1 to 4)
The positive electrode and negative electrode shown in Table 2 are punched into 45 mm × 40 mm and 50 mm × 45 mm, respectively, and a separator (porous polypropylene film) inserted between them is inserted into an aluminum laminated bag, and after vacuum drying, an electrolytic solution ( After injecting LiPF 6 at a concentration of 1M) into a mixed solvent in which ethylene carbonate and diethyl carbonate are mixed at a ratio of 1: 1 (volume ratio), the aluminum laminate is sealed and laminated. Type lithium ion battery was produced. Laminate type lithium ion batteries are manufactured in a glove box substituted with argon gas, and after making laminated type lithium ion batteries, the battery characteristics are evaluated for initial resistance, resistance increase, rate characteristics and cycle characteristics shown below. It was. Examples 45 and 46 are reference examples.
(抵抗測定)
放電電流12mA(0.2C)にて放電終止電圧3.0Vで定電流放電を行ったラミネート型電池を、インピーダンスアナライザー(biologic社製SP−50)にて500kHzでの抵抗測定を行った。
上述したラミネート型電池を25℃から180℃まで加熱し、各々の温度での抵抗測定を行った。25℃で測定した抵抗を初期抵抗とし、180℃で測定した抵抗値と25℃で測定した抵抗値の商を抵抗増加とした。すなわち抵抗増加は以下(式1)で表される。
(式1) 抵抗増加=180℃での抵抗値/25℃での抵抗値
初期抵抗および抵抗増加について、以下の基準で評価した結果を表2に示す。
・初期抵抗
○:「初期抵抗が下地層なしの比較例1の初期抵抗より小さい。優れている。」
△:「初期抵抗が下地層なしの比較例1の初期抵抗と同等。」
×:「初期抵抗が下地層なしの比較例1の初期抵抗より大きい。劣っている。」
・抵抗増加
○:「抵抗増加が初期抵抗の5倍以上。優れている。」
△:「抵抗増加が初期低能の3倍以上、5倍未満。電流の遮断効果が不十分。」
×:「抵抗増加が初期抵抗の3倍未満。電流の遮断効果が低い。劣っている。」
(Resistance measurement)
A laminate type battery that was discharged at a constant discharge current of 3.0 V at a discharge current of 12 mA (0.2 C) was subjected to resistance measurement at 500 kHz with an impedance analyzer (SP-50 manufactured by biologic).
The laminate type battery described above was heated from 25 ° C. to 180 ° C., and resistance measurement was performed at each temperature. The resistance measured at 25 ° C. was taken as the initial resistance, and the quotient of the resistance value measured at 180 ° C. and the resistance value measured at 25 ° C. was taken as the resistance increase. That is, the increase in resistance is expressed by the following (formula 1).
(Equation 1) Resistance increase = resistance value at 180 ° C./resistance value at 25 ° C. The results of evaluating the initial resistance and the resistance increase according to the following criteria are shown in Table 2.
Initial resistance ○: “The initial resistance is smaller than the initial resistance of Comparative Example 1 without an underlayer. Excellent.”
Δ: “The initial resistance is equivalent to the initial resistance of Comparative Example 1 without the underlayer”
X: “The initial resistance is larger than the initial resistance of Comparative Example 1 without the underlayer. Inferior”
・ Increased resistance ○: “Increased resistance is more than 5 times the initial resistance. Excellent”
Δ: “Increase in resistance is 3 times or more and less than 5 times the initial low ability. Insufficient current blocking effect”
X: “Increased resistance is less than 3 times the initial resistance. Current blocking effect is low. Inferior”
(レート特性)
上述したラミネート電池について、充放電装置(北斗電工社製SM−8)を用い、充放電測定を行った。
充電電流12mA(0.2C)にて充電終止電圧4.2Vで定電流定電圧充電(カットオフ電流0.6mAを行った後、放電電流12mA(0.2C)および120mA(2C)で放電終止電圧3.0Vに達するまで定電流放電を行って、それぞれ放電容量を求めた。レート特性は0.2C放電容量と2C放電容量の比、つまり以下(式2)で表される。
(式2) レート特性=2C放電容量/0.2C放電容量×100(%)
以下の基準で評価した結果を表2に示す。
・レート特性
○:「レート特性が80%以上。特に優れている。」
○△:「レート特性が75%以上、80%未満。優れている。」
△:「レート特性が70以上、75%未満。下地層なしの比較例1のレート特性と同等。」
×:「レート特性が70%未満。劣っている。」
(Rate characteristics)
About the laminated battery mentioned above, charging / discharging measurement was performed using the charging / discharging apparatus (SM-8 by Hokuto Denko).
Constant current and constant voltage charge with a charge current of 12 mA (0.2 C) and a charge end voltage of 4.2 V (after a cut-off current of 0.6 mA, the discharge was terminated at a discharge current of 12 mA (0.2 C) and 120 mA (2 C). The constant current discharge was performed until the voltage reached 3.0 V, and the discharge capacity was obtained, respectively, and the rate characteristic is expressed by the ratio of the 0.2 C discharge capacity to the 2 C discharge capacity, that is, the following (Equation 2).
(Equation 2) Rate characteristics = 2C discharge capacity / 0.2C discharge capacity × 100 (%)
Table 2 shows the results of evaluation based on the following criteria.
・ Rate characteristic ○: “Rate characteristic is 80% or more. Particularly excellent.”
○ △: “Rate characteristic is 75% or more and less than 80%. Excellent”
Δ: “The rate characteristic is 70 or more and less than 75%. Equivalent to the rate characteristic of Comparative Example 1 without a base layer.”
X: “Rate characteristic is less than 70%. Inferior”
(サイクル特性)
50℃恒温槽にて充電電流を60mAにて充電終止電圧を4.2Vで定電流定電圧充電(カットオフ電流0.6mA)を行った後、放電電流60mAで放電終止電圧3.0Vに達するまで定電流放電を行って、初回放電容量を求めた。この充放電サイクルを200回行い、放電容量維持率(初回放電容量に対する200回目の放電容量の百分率)を算出した。以下の基準で評価した結果を表2に示す。
・サイクル特性
○:「放電容量維持率が90%以上。特に優れている。」
○△:「放電容量維持率が85%以上、90%未満。優れている。」
△:「放電容量維持率が80%以上、85%未満。下地層なしの比較例1の放電容量維持率と同等。」
×:「放電容量維持率が80%未満。劣っている。」
(Cycle characteristics)
After performing constant current and constant voltage charging (cutoff current 0.6 mA) at a charge current of 60 mA and a charge end voltage of 4.2 V in a 50 ° C. constant temperature bath, the discharge current reaches 60 V at a discharge current of 60 mA. The initial discharge capacity was obtained by performing constant current discharge until. This charge / discharge cycle was performed 200 times, and the discharge capacity maintenance ratio (percentage of the 200th discharge capacity with respect to the initial discharge capacity) was calculated. Table 2 shows the results of evaluation based on the following criteria.
Cycle characteristics ○: “Discharge capacity maintenance rate is 90% or more. Particularly excellent.”
○ △: “Discharge capacity maintenance ratio is 85% or more and less than 90%. Excellent”
Δ: “Discharge capacity maintenance ratio is 80% or more and less than 85%. Equivalent to the discharge capacity maintenance ratio of Comparative Example 1 without a base layer.”
×: “Discharge capacity maintenance rate is less than 80%. Inferior”
表2に示すように、本発明の導電性組成物から形成された下地層を用いることで、電池の内部温度が上昇した場合、電池の内部抵抗が上昇することが確認された。このことから、例えば、内部短絡などにより電池が異常発熱した場合、集電体の抵抗が増大し、電流を遮断することで、電池の発火等を回避するものと考えられる。
一方、下地層を形成していない比較例1や、本発明以外の水分散樹脂微粒子(C)からなる下地層を形成した比較例2や、本発明の水分散樹脂微粒子(C)以外の樹脂からなる下地層を形成した比較例3および4では、電池の内部温度が上昇しても、目立った電池の内部抵抗の上昇は見られなかった。比較例1は下地層を形成していないため、発熱時に抵抗を増大させる効果がなく、比較例2および4では、発熱時における樹脂の体積膨張が不十分なため、導電層中に分散している導電性の炭素材料同士を引き剥がすことができなかったためと考えられる。さらに、比較例3では、下地層内でのポリオレフィン樹脂の分散性が不均一なため、局所的に導電性の炭素材料同士の接触を引き剥がすことができなかったためと考えられ、さらには、導電性の炭素材料やポリオレフィン樹脂の分散性が不均一なことで、下地層の導電性が悪化し、レート特性やサイクル特性が悪化したと考えられる。
実施例45、46に示すように、水溶性樹脂(B)およびポリオレフィン樹脂微粒子(C)の含有量が少なすぎると、加熱による抵抗上昇はそれほど高くない結果が得られた。実施例45では、水分散樹脂微粒子(C)の含有量が少なく、ポリオレフィン樹脂の体積膨張が十分に発現しなかったためと考える。また、実施例46では、水溶性樹脂(B)の含有量が少なく、加熱によるポリオレフィンの体積膨張と同時に起こると思われる樹脂の溶融を抑えることができず、炭素材料同士の切断が出来なかったためと考えられる。
実施例15、25.26、29に示すように、オレフィン系の水分散樹脂微粒子(C)を用いても、カルボン酸またはカルボン酸エステルの変性量が少ないもの、または未変性のものは、加熱による抵抗上昇はそれほど高くない結果が得られた。これは、加熱により、ポリオレフィン樹脂の体積膨張と溶融が同時に起こるため、炭素材料同士の切断を効果的に引き起こすことができなかったためと考えられる。このことから、ポリオレフィン樹脂は一定量以上の変性によって、溶融を抑制していると考えられる。
実施例35、36に示すように、炭素材料であるカーボンブラックの二次凝集体を小さくしたものは、加熱による抵抗上昇はそれほど高くない結果が得られた。この理由についてはまだ明確となっていないが、下地層内部での各材料の存在形態が変化したため、炭素材料同士の切断を効果的に行えなかったと推定している。
実施例24に示すように、カーボンブラックの体積平均粒子径よりも大きい水分散樹脂を用いたものは、加熱による抵抗上昇はそれほど高くない結果が得られた。これは、水分散樹脂粒子が大きすぎるため、炭素材料同士の切断を効果的に行えなかったためと推定している。
以上の結果から、本発明によって、電池の出力特性等に優れ、過充電や内部短絡などにより電池の内部温度が上昇した場合に、内部抵抗を上昇させることで流れる電流を抑制することで、電池の安全性を高める機能を備えた非水電解質二次電池を形成するための導電性組成物を提供することができる。
As shown in Table 2, it was confirmed that the internal resistance of the battery increased when the internal temperature of the battery increased by using the base layer formed from the conductive composition of the present invention. From this, for example, when the battery abnormally heats up due to an internal short circuit or the like, it is considered that the resistance of the current collector increases and the current is cut off to avoid ignition of the battery.
On the other hand, Comparative Example 1 in which no underlayer is formed, Comparative Example 2 in which an underlayer composed of water-dispersed resin fine particles (C) other than the present invention is formed, and resins other than the water-dispersed resin fine particles (C) of the present invention In Comparative Examples 3 and 4 in which the base layer made of was formed, even if the internal temperature of the battery increased, no noticeable increase in the internal resistance of the battery was observed. Since Comparative Example 1 does not form a base layer, there is no effect of increasing resistance during heat generation. In Comparative Examples 2 and 4, since the volume expansion of the resin during heat generation is insufficient, it is dispersed in the conductive layer. This is probably because the conductive carbon materials that were present could not be peeled off. Furthermore, in Comparative Example 3, it is considered that the dispersibility of the polyolefin resin in the underlayer was non-uniform, so that contact between the conductive carbon materials could not be peeled off locally. It is considered that the dispersibility of the functional carbon material and the polyolefin resin is not uniform, the conductivity of the underlayer is deteriorated, and the rate characteristics and the cycle characteristics are deteriorated.
As shown in Examples 45 and 46, when the content of the water-soluble resin (B) and the polyolefin resin fine particles (C) was too small, the resistance increase due to heating was not so high. In Example 45, it is considered that the content of the water-dispersed resin fine particles (C) was small, and the volume expansion of the polyolefin resin was not sufficiently exhibited. Further, in Example 46, the content of the water-soluble resin (B) is small, and the melting of the resin that seems to occur simultaneously with the volume expansion of the polyolefin due to heating could not be suppressed, and the carbon materials could not be cut. it is conceivable that.
As shown in Examples 15, 25.26, and 29, even when the olefin-based water-dispersed resin fine particles (C) are used, those having a small amount of modification of carboxylic acid or carboxylic acid ester, or unmodified are heated. The increase in resistance due to was not so high. This is presumably because the volume expansion and melting of the polyolefin resin occur simultaneously by heating, and thus the carbon materials could not be effectively cut. From this, it is considered that the polyolefin resin suppresses melting by a certain amount of modification.
As shown in Examples 35 and 36, when the carbon black secondary aggregate of the carbon material was made small, the resistance increase due to heating was not so high. Although the reason for this has not been clarified yet, it is presumed that the carbon material cannot be cut effectively because the existence form of each material in the underlayer has changed.
As shown in Example 24, in the case of using a water-dispersed resin larger than the volume average particle diameter of carbon black, the result of resistance increase due to heating was not so high. This is presumably because the water-dispersed resin particles were too large to cut the carbon materials effectively.
From the above results, according to the present invention, the battery has excellent output characteristics and the like, and when the internal temperature of the battery rises due to overcharge, internal short circuit, etc., the current flowing is suppressed by increasing the internal resistance. It is possible to provide a conductive composition for forming a non-aqueous electrolyte secondary battery having a function of improving the safety of the battery.
Claims (10)
A nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and an electrolyte solution, wherein at least one of the positive electrode or the negative electrode is an electrode for a nonaqueous electrolyte secondary battery according to claim 9. Secondary battery.
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CN201680019021.5A CN107429009B (en) | 2015-03-30 | 2016-03-18 | Conductive composition and method for producing same, collector with base layer for electricity storage device, electrode for electricity storage device, and electricity storage device |
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