JP2005085557A - Manufacturing method of slurry composition for secondary lithium-ion battery electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a slurry composition for a lithium-ion secondary battery electrode in which the smoothness of the electrode surface is attained in the electrode and the solid content is sufficiently dispersed. <P>SOLUTION: This is the manufacturing method of a slurry composition for the lithium-ion secondary battery electrode which has a process (I) of obtaining a kneaded product of funicular state by kneading a water soluble polymer, an electrode active material, a conductivity donating material, and water and a process (II) of mixing the kneaded product, a water dispersion solution of an acrylic polymer having a glass transition temperature of 20°C or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a slurry composition for a lithium ion secondary battery electrode and a method for producing an electrode for a lithium ion secondary battery using the slurry composition.

  Secondary batteries such as lithium ion secondary batteries are frequently used as power sources for portable terminals such as notebook personal computers, mobile phones, and PDAs, which have been widely used in recent years.

  In an electrode for a lithium ion secondary battery, an electrode binder (hereinafter sometimes simply referred to as “binder”) is dissolved or dispersed in water or an organic solvent, and an active material, a conductivity imparting material, or the like is mixed therewith. The slurry composition for a lithium ion secondary battery electrode obtained in this manner (hereinafter sometimes simply referred to as “slurry composition”) is applied to a current collector and dried. However, in some cases, solid contents such as an active material and a conductivity imparting material are not uniformly dispersed in the slurry composition. If a slurry composition with insufficient solid content is used, the coating property on the current collector may deteriorate and the electrode may become non-uniform, or agglomerates may remain on the electrode surface and short circuit during battery creation. there were.

  When the dispersion medium of the slurry composition is water, it is usual to add a thickener such as carboxymethylcellulose for the purpose of imparting fluidity to the slurry composition and improving the coating property to the current collector. is there. As a method for obtaining a slurry composition in which the solid content is uniformly dispersed, a thickener is added to the active material and the conductivity-imparting material at least twice and kneaded, followed by polytetrafluoroethylene (PTFE). A method of adding a binder such as) and kneading has been proposed (see Patent Document 1).

  Also, mixing treatment with a strong shearing force is performed in the mixing step before the addition of the binder to promote primary particle formation of solids, and a mixing treatment is performed with a weak shearing force in the mixing step after the addition of the binder to prevent the binder from aggregating. A method has also been proposed (see Patent Document 2).

JP 2000-348713 A Japanese Patent Laid-Open No. 11-213990

  However, in these methods using PTFE as a binder, the surface smoothness of the electrode may be affected by fluctuations in adjustment conditions. Further, the binding force of the obtained electrode was not sufficient. Under such circumstances, an object of the present invention is to provide a method for producing a slurry composition for a lithium ion secondary battery electrode with a highly dispersed solid content, which gives an electrode with good electrode surface smoothness. .

  As a result of intensive studies to solve the above problems, the inventors of the present invention kneaded a water-soluble polymer, an electrode active material, a conductivity-imparting material, and water into a funicular state, and then a glass transition temperature of 20 ° C. or lower. It was found that a slurry composition in which the solid content was highly dispersed and no agglomerates was obtained by mixing an aqueous dispersion of the acrylate polymer. Furthermore, when manufacturing an electrode using this slurry composition, it discovered that an electrode excellent in surface smoothness and high binding strength was obtained, and came to complete this invention based on these knowledge.

Thus, according to the present invention, the step (I) of kneading a water-soluble polymer, an electrode active material, a conductivity-imparting material, and water to obtain a kneaded product in a funicular state, the kneaded product, and the glass transition temperature And a method for producing a slurry composition for a lithium ion secondary battery electrode, comprising a step (II) of mixing an aqueous dispersion of an acrylate polymer at 20 ° C. or lower.
In the step (I), a water-soluble polymer, a conductivity-imparting material, and water are mixed to obtain a conductivity-imparting material dispersion (I-1), and an electrode active material is added to the conductivity-imparting material dispersion And kneading (I-2).

The step (II) includes a step (II-1) of diluting the kneaded material and then dispersing the mixture with a disperser having a peripheral speed of 0.5 to 200 m / sec, and the obtained dispersion and the acrylate system. It is preferable to have the process (II-2) which mixes with the polymer aqueous dispersion.
Furthermore, in the step (II-2), it is preferable to mix at a peripheral speed of less than 0.5 m / sec.
The average particle size of the electrode active material in the obtained slurry composition for lithium ion secondary battery electrodes is preferably 1.3 times or less of the primary particle size.

  According to the present invention, it is possible to obtain a slurry composition for a lithium ion secondary battery electrode in which solid contents such as an electrode active material and a conductivity-imparting material are highly dispersed and free from aggregates. Since the slurry composition obtained by the method of the present invention is excellent in coating properties, when an electrode for a lithium ion secondary battery is prepared using the slurry composition, the surface smoothness of the electrode layer is excellent, and the binding strength is high. Large electrodes can be obtained.

Hereinafter, the present invention will be described in detail for each process.
Step (I):
The method for producing a slurry composition for a lithium ion secondary battery electrode of the present invention comprises a step of kneading a water-soluble polymer, an electrode active material, a conductive material, and water to obtain a kneaded product in a funicular state (I ).

Examples of the water-soluble polymer used in the present invention include cellulosic polymers such as carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, and ammonium salts and alkali metal salts thereof; (modified) poly (meth) acrylic acid and ammonium salts and alkalis thereof. Metal salts; Saponification products of copolymers of unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid and fumaric acid and vinyl esters; (Modification) Copolymerization of polyvinyl alcohol, acrylic acid or acrylate and vinyl alcohol Polyvinyl alcohols such as copolymers, maleic anhydride or copolymers of maleic acid or fumaric acid and vinyl alcohol; polyethylene glycol, polyethylene oxide, polyvinyl pyrrolidone, modified polyacrylic acid, oxidized starch, Phosphate starch, casein, various modified starch.
Among these, cellulose polymers and salts thereof, and poly (meth) acrylic acid are preferable, alkali metal salts of carboxymethyl cellulose are more preferable, and lithium salts of carboxymethyl cellulose are particularly preferable. The amount of these water-soluble polymers used is usually 0.1 to 15 parts by weight, preferably 0.1 to 10 parts by weight, more preferably 0.1 to 8 parts by weight with respect to 100 parts by weight of the electrode active material. . The water-soluble polymer acts as a thickener, contributes to improving the coating properties of the slurry composition, and also acts as a dispersant for the electrode active material and the conductivity-imparting material.

The electrode active material used in the present invention is appropriately selected depending on the type of electrode. The slurry composition obtained by the production method of the present invention can be used for both the positive electrode and the negative electrode, but is preferably used for the positive electrode. Any electrode active material can be used as long as it is used in a normal lithium ion secondary battery. As an electrode active material for a positive electrode of a lithium ion secondary battery, lithium-containing composite metal oxides such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiFeVO ₄ ; TiS ₂ , TiS ₃ , non Transition metal sulfides such as crystalline MoS ₃ ; transition metal oxides such as Cu ₂ V ₂ O ₃ , amorphous V ₂ O—P ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ ; Illustrated. Further, a conductive polymer such as polyacetylene or poly-p-phenylene can be used.

  Examples of the electrode active material for the negative electrode of the lithium ion secondary battery include carbonaceous materials such as amorphous carbon, graphite, natural graphite, mesocarbon microbeads (MCMB), pitch-based carbon fibers, and conductive materials such as polyacene. Examples thereof include polymers. As the electrode active material, a material obtained by attaching a conductivity imparting material to the surface by a mechanical modification method can also be used.

  The primary particle diameter of the electrode active material is usually 0.5 to 50 μm. Here, the primary particle size is an average particle size measured using a laser diffraction particle size distribution measuring device for a dispersion obtained by dispersing an electrode active material in water and performing ultrasonic treatment.

  As the conductivity-imparting material used in the present invention, carbonaceous materials such as graphite, activated carbon, acetylene black, ketjen black, furnace black, graphite, carbon fiber, fullerenes, conductive polymers, metal powders, and the like are used. Of these, acetylene black and furnace black are preferable. The usage-amount of a conductive provision material is 0.5-20 weight part normally with respect to 100 weight part of electrode active materials, Preferably it is 1-10 weight part.

In the method of the present invention, the water-soluble polymer, the electrode active material, the conductivity-imparting material, and water are kneaded to obtain a kneaded product in a funicular state. The funicular state is a state in which the solid phase and the liquid phase are both continuous phases in the filled state of the solid / liquid mixed system. In the funicular state, the gas phase may be a continuous phase or a discontinuous phase. When the gas phase is a continuous phase, the funicular I state, and when the gas phase is a discontinuous phase, the funicular II state It is called.
The kneaded product obtained in the step (I) of the present invention may be in either the funicular I state or the funicular II state, but can impart a strong shearing force during kneading and can disperse the solid content more uniformly. It is preferable to adjust the solid content concentration so that a funicular I state is obtained.

  As a mixer used for kneading, a mixer capable of imparting a high shearing force is preferable. Specific examples include blade-type stirrers such as planetary mixers and kneaders; single-screw or twin-screw extruders, and the like. Among these, a blade type stirrer is preferable, and a planetary mixer is more preferable. As a planetary mixer, if a triaxial type equipped with a stirring blade capable of high-speed rotation such as a disper is used, the obtained kneaded material is also transferred to another container (II-1) described later without being transferred to another container. Since it can be used, it is especially preferable.

  The kneading conditions vary depending on the type and particle size of each component used, but the solid content concentration is usually 50 to 90% by weight, preferably 70 to 90% by weight, more preferably 75 to 90% by weight. When a blade type stirrer is used, the peripheral speed of the stirring blade is usually 0.1 to 2 m / second, preferably 0.1 to 1 m / second, and the kneading time is usually 20 to 60 minutes, preferably 30 to 60. Minutes. The temperature and pressure at the time of kneading are not particularly limited, and may be ordinary temperature or normal pressure.

  In the present invention, each of the above components may be mixed and kneaded together, but a step (I-1) of obtaining a conductive material dispersion by mixing a water-soluble polymer, a conductive material, and water. And it is preferable to mix in two steps of the process (I-2) of adding and kneading an electrode active material to this electrically conductive provision material dispersion liquid. By conducting the mixing in two stages, the conductivity-imparting material can be more uniformly dispersed. The average particle diameter of the conductivity-imparting material in the conductivity-imparting material dispersion obtained in the step (I-1) is preferably 1 μm or less.

  The solid content concentration in the step (I-1) is usually 25 to 50% by weight, preferably 27 to 40% by weight. The mixing method is not particularly limited, and for example, by using a planetary mixer and mixing at a peripheral speed of 0.1 to 1 m / sec for 30 to 60 minutes, a conductivity imparting material dispersion can be obtained.

Step (II):
The manufacturing method of the slurry composition for lithium ion secondary battery electrodes of this invention mixes the kneaded material obtained at the said process (I), and the aqueous dispersion of the acrylate polymer whose glass transition temperature is 20 degrees C or less. It has process (II). In this step (II), the kneaded product is diluted and an aqueous dispersion of an acrylate polymer as a binder is uniformly mixed to obtain a slurry composition. The viscosity of the resulting slurry composition is usually 2 to 13 Pa · s.

  The acrylate polymer used in the present invention is a polymer containing a monomer unit derived from an acrylate ester and / or a methacrylic acid ester, and preferably an acrylic such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, etc. It is a polymer mainly composed of an acid alkyl ester unit. The content of the acrylic acid alkyl ester unit is usually 50% by weight or more, preferably 60 to 95% by weight, more preferably 65 to 90% by weight. Since the acrylate polymer has hydrophilicity, it is excellent in dispersibility in the slurry composition.

  The acrylate polymer may contain other monomer units copolymerizable with an acrylic ester or a methacrylic ester. Other copolymerizable monomers include α, β-unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and itaconic acid; ethylene glycol dimethacrylate, And polyfunctional ethylenically unsaturated monomers such as diethylene glycol dimethacrylate and trimethylolpropane trimethacrylate; Among these, it is preferable to have an ethylenically unsaturated carboxylic acid unit of 0.1 to 10% by weight, particularly 1 to 7% by weight, because the dispersibility of the electrode active material is excellent. Further, it is preferable to copolymerize a polyfunctional ethylenically unsaturated monomer in an amount of 0.3 to 5% by weight, particularly 0.5 to 4% by weight, because it is excellent in binding properties and electrolyte resistance. .

  Preferable specific examples of the acrylate polymer used in the present invention include 2-ethylhexyl acrylate / methacrylic acid / acrylonitrile / ethylene glycol dimethacrylate copolymer, 2-ethylhexyl acrylate / methacrylic acid / methacrylonitrile / diethylene glycol dimethacrylate. Examples include copolymers, butyl acrylate / acrylonitrile / diethylene glycol dimethacrylate copolymers, butyl acrylate / acrylic acid / trimethylolpropane trimethacrylate copolymers, and the like.

  The glass transition temperature (Tg) of the acrylate polymer used in the present invention is 20 ° C. or less, preferably −80 ° C. to 0 ° C., more preferably −50 ° C. to −10 ° C. When Tg is too high, the flexibility and binding properties of the electrode are lowered, and peeling of the electrode layer from the current collector tends to occur.

  The usage-amount of the acrylate type polymer in the manufacturing method of this invention becomes like this. Preferably it is 0.1-20 weight% with respect to an electrode active material, More preferably, it is 0.5-10 weight%. If the amount of the acrylate polymer is too small, the electrode active material tends to fall off from the electrode. Conversely, if the amount is too large, the electrode active material may be covered with the acrylate polymer and the internal resistance of the electrode may increase.

  In the production method of the present invention, the acrylate polymer is used as an aqueous dispersion. It is preferable to produce an acrylate polymer by an emulsion polymerization method because the acrylate polymer can be obtained as a latex aqueous dispersion. The obtained latex can be used in the production method of the present invention as it is without isolating the polymer or after adjusting the concentration by concentration, dilution or the like, if necessary. The concentration (solid content) of the acrylate polymer in water is usually 20 to 70% by weight, preferably 30 to 60% by weight.

  The mixing conditions may be adjusted as appropriate so that the electrode active material and the conductivity-imparting material are uniformly dispersed and the acrylate polymer does not aggregate. If the dispersion is insufficient, the electrode active material may aggregate to form secondary particles, which may reduce the smoothness of the electrode surface. The average particle diameter of the electrode active material in the slurry composition obtained by the production method of the present invention is preferably 1.3 times or less, more preferably 1.2 times or less, particularly preferably 1. 1 time or less. Here, the average particle diameter of the electrode active material in the slurry composition is an apparent particle diameter including particles that are secondary particles by aggregation, and is obtained by dispersing 1 part of the slurry composition in 20 parts of water. It is an average particle diameter measured using a laser diffraction type particle size distribution measuring device.

  From the viewpoint of obtaining a slurry composition in which each component is uniformly dispersed, in the step (II), the kneaded material obtained in the step (I) is diluted and then dispersed at a peripheral speed of 0.5 to 200 m / sec. It is preferable to carry out in two steps, the treatment step (II-1) and the step (II-2) of mixing the obtained dispersion and the aqueous dispersion of the acrylate polymer.

  In step (II-1), first, the kneaded material obtained in step (I) is diluted with water. The solid content concentration is usually adjusted to 30 to 75% by weight, preferably 35 to 70% by weight. Subsequently, using a stirrer, the dispersion treatment is performed by stirring at a peripheral speed of 0.5 to 200 m / sec, preferably 1 to 180 m / sec, more preferably 2 to 170 m / sec. The time for the dispersion treatment is usually 5 to 30 minutes, preferably 15 to 30 minutes. Any stirrer can be used as long as it has a stirring blade capable of rotating at high speed, but a disper, a homogenizer, or the like is preferable. Further, it is more preferable to use a planetary mixer with a disper together with a planetary mixing section and a disper, since uniform dispersion can be achieved with a short dispersion process. By this step, the fine agglomerates generated in step (I) are disassembled, and a slurry composition in which the electrode active material and the conductivity-imparting material are highly dispersed can be obtained.

  In step (II-2), the dispersion obtained in step (II-1) and the aqueous dispersion of the acrylate polymer are mixed. As the mixer, one that can be uniformly mixed with a weak shearing force is preferable. Specifically, a planetary mixer is preferably used. Moreover, you may use the disperser provided with rotary blades, such as a disper. The peripheral speed of the mixer during mixing is usually less than 0.5 m / sec, preferably 0.1 to 0.3 m / sec. The mixing time is usually 5 to 30 minutes, preferably 15 to 30 minutes. In the step (II-1), since the electrode active material and the conductivity-imparting material in the dispersion liquid are highly dispersed, even in the step (II-2), even if they are mixed with a weak shearing force, the acrylate polymer is Easily uniformly dispersed. If the shearing force is too strong, the acrylate polymer may aggregate and the slurry composition may become non-uniform.

  The slurry composition obtained by the method of the present invention can be applied to a current collector and dried according to a conventional method to obtain an electrode for a lithium ion secondary battery. As the current collector, a conductive material is used, and metals such as iron, copper, aluminum, nickel, and stainless steel are preferable. The shape of the current collector is not particularly limited, but a sheet shape having a thickness of about 0.001 to 0.5 mm is preferable.

  The method for applying the slurry composition to the current collector is not particularly limited. Examples of the method include a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, and a brush coating method. The amount of the slurry composition to be applied is not particularly limited, but the amount of the electrode layer formed after drying and made of an electrode active material, a binder, etc. is usually 0.005 to 5 mm, preferably 0.01 to 2 mm. Is common. The drying method is not particularly limited, and examples thereof include drying by warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. The drying speed is adjusted so that the liquid medium can be removed as quickly as possible within a speed range in which the electrode layer is not cracked due to stress concentration or the electrode layer does not peel from the current collector. Furthermore, you may raise the density of the active material of an electrode by pressing the collector after drying. Examples of the pressing method include a mold press and a roll press.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto. In the examples and comparative examples, parts,% and ppm are based on weight unless otherwise specified.

The tests and evaluations in the examples and comparative examples were performed by the following methods.
(1) Glass transition temperature (Tg)
The Tg of the acrylate polymer was measured by raising the temperature at 10 ° C./min with a differential scanning calorimeter (DSC).
(2) Measurement of the particle diameter of the electrode active material The primary particle diameter of the electrode active material is 1000 times the dispersion obtained by dispersing the electrode active material in water at a concentration of 5% and sonicating for 2 minutes. It diluted and measured using the laser diffraction type particle size distribution measuring apparatus (SALD2000: Shimadzu Corp. make).
Further, the average particle size of the electrode active material in the slurry composition was measured in the same manner as described above for a dispersion obtained by dispersing 1 part of the slurry composition in 20 parts of water.

(3) Peel strength
Production of electrode for positive electrode A slurry composition for positive electrode was uniformly applied to one side of an aluminum foil (thickness 20 μm) by a doctor blade method, first dried at 60 ° C. for 10 minutes, and then 120 ° C. for 20 minutes. The positive electrode was obtained by compressing the electrode density to 3.3 g / cm ³ by a biaxial roll press.
Production of Electrode for Negative Electrode The slurry composition for negative electrode was uniformly applied to one side of a copper foil (thickness 18 μm) by a doctor blade method and dried under the same conditions as those for the positive electrode. The negative electrode was obtained by compressing with a biaxial roll press so that the electrode density was 1.4 g / cm ³ .
Measurement of Peel Strength The electrode (positive electrode or negative electrode) obtained by the above method is cut into a rectangle having a width of 2.5 cm and a length of 10 cm to form a test piece, and fixed with the electrode layer surface facing up. After the cellophane tape was attached to the electrode layer surface of the test piece, the stress was measured when the cellophane tape was peeled from the one end of the test piece in the direction of 180 ° at a speed of 50 mm / min. The measurement was performed 10 times, the average value was obtained, and this was taken as the peel strength. The higher the peel strength, the greater the binding force of the electrode layer to the current collector.

(4) Surface smoothness The electrode obtained by the method described in (3) above was cut into a rectangle having a width of 1 cm and a length of 8 cm, and the surface roughness Ra was measured with a contact-type surface tester.

[Production Example 1]
In an autoclave with a stirrer, 150 parts of ion exchange water, 80 parts of 2-ethylhexyl acrylate, 5 parts of acrylic acid, 14 parts of methacrylonitrile, 1 part of ethylene glycol dimethacrylate, 3 parts of sodium dodecylbenzenesulfonate and potassium persulfate After 3 parts were added and stirred sufficiently, the polymerization was started by heating to 60 ° C. Polymerization was performed for 10 hours to obtain an aqueous dispersion (latex B-1) of an acrylate polymer having a solid content concentration of 41%. The polymerization conversion rate determined from the solid content concentration was approximately 99%. The obtained acrylate polymer had a Tg of -50 ° C.

[Production Example 2]
In an autoclave equipped with a stirrer, 150 parts of ion exchange water, 80 parts of butyl acrylate, 5 parts of acrylic acid, 13 parts of acrylonitrile, 2 parts of ethylene glycol dimethacrylate, 3 parts of sodium dodecylbenzenesulfonate and 3 parts of potassium persulfate After sufficiently stirring, the polymerization was started by heating to 60 ° C. Polymerization was carried out for 10 hours to obtain an aqueous dispersion (latex B-2) of an acrylate polymer having a solid content concentration of 41%. The polymerization conversion rate determined from the solid content concentration was approximately 99%. The obtained acrylate polymer had a Tg of -34 ° C.

[Example 1] (Production of positive electrode slurry composition)
A planetary mixer is charged with 3 parts of acetylene black (manufactured by Denki Kagaku) as a conductivity-imparting material, and 8 parts of a 2.5% aqueous solution of Serogen WSC (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a thickener. Rotated at 3 m / sec and mixed for 60 minutes at a solids concentration of 29%. Thereafter, 8 parts of a 2.5% aqueous solution of Serogen WSC was added and mixed for 15 minutes, and further 8 parts of a Serogen WSC aqueous solution was added and mixed for 15 minutes to prepare a conductivity imparting material dispersion.
A planetary mixer with a disper is charged with 100 parts of lithium cobalt oxide having an average particle size of 7.1 μm as an electrode active material and 27 parts of the conductive material dispersion liquid, and only the planetary mixer is rotated at a peripheral speed of 0.3 m / sec. The mixture was kneaded for 60 minutes at a solid concentration of 81.5%. Thereafter, water was added to obtain a solid content concentration of 70%, and dispersion treatment was carried out for 20 minutes using a planetary mixer with a peripheral speed of 0.3 m / sec and a disper with a peripheral speed of 50 m / sec. To this dispersion, 1.7 parts of latex B-1 is added based on the solid content, and only the planetary mixer is rotated at a peripheral speed of 0.2 m / second and mixed for 30 minutes to obtain a solid content of 69.2% for the positive electrode. A slurry composition was obtained. The average particle diameter of the electrode active material in this slurry composition was 7.2 μm. The peel strength of the positive electrode produced using this slurry composition was 4 g / cm, and Ra was 0.9 μm.

[Example 2]
A slurry composition for positive electrode was obtained in the same manner as in Example 1 except that latex B-2 was used as the acrylate polymer and the peripheral speed of the disperser before addition of latex B-2 was 120 m / sec. The average particle diameter of the electrode active material in this slurry composition was 6.9 μm. The peel strength of the positive electrode produced using this slurry composition was 4 g / cm, and Ra was 0.8 μm.

[Comparative Example 1]
A planetary mixer was charged with 100 parts of lithium cobalt oxide having an average particle diameter of 7.1 μm as an electrode active material and 27 parts of the conductivity-imparting material dispersion obtained in Example 1, and the planetary mixer was rotated at a peripheral speed of 0.3 m / second. And kneaded for 60 minutes at a solid content concentration of 81.5%. Thereafter, water was added to achieve a solid content concentration of 70%, and kneading was continued for another 20 minutes. 7.5 parts of a 50% aqueous PTFE dispersion was added to the obtained dispersion based on the solid content, and the planetary mixer was rotated at a peripheral speed of 0.3 m / second and mixed for 30 minutes to obtain a solid content concentration of 66.6. % Slurry composition for positive electrode was obtained. The average particle diameter of the electrode active material in this slurry composition was 8.0 μm. The peel strength of the positive electrode produced using this slurry composition was 3 g / cm, and Ra was 1.2 μm.

[Comparative Example 2]
A planetary mixer with a disperser is charged with 100 parts of lithium cobaltate having an average particle diameter of 7.1 μm, 3 parts of acetylene black, 24 parts of a 2.5% aqueous solution of serogen WSC and 1.7 parts of latex B-1 on a solid basis, Only the Lee mixer was rotated at a peripheral speed of 0.3 m / sec and kneaded for 60 minutes at a solid concentration of 75%. Thereafter, water was added to obtain a solid content concentration of 70%, and dispersion treatment was carried out for 20 minutes using a planetary mixer with a peripheral speed of 0.3 m / sec and a disper with a peripheral speed of 50 m / sec. Furthermore, only the planetary mixer was rotated at a peripheral speed of 0.25 m / sec and mixed for 30 minutes to obtain a slurry composition for positive electrode having a solid content concentration of 70%. The average particle diameter of the electrode active material in this slurry composition was 10.1 μm. The peel strength of the positive electrode produced using this slurry composition was 3 g / cm, and Ra was 2.1 μm.

[Example 3] (Production of slurry composition for negative electrode)
A planetary mixer with a disper was charged with 100 parts of artificial graphite having an average particle diameter of 25.5 μm as an electrode active material, 35 parts of the conductivity imparting material dispersion obtained in Example 1, and 17.6 parts of water. The mixture was rotated at a peripheral speed of 0.3 m / sec and kneaded at a solid content concentration of 68% for 60 minutes. Thereafter, water was added to obtain a solid concentration of 55%, and a dispersion treatment was carried out for 20 minutes using a planetary mixer with a peripheral speed of 0.3 m / second and a disper with a peripheral speed of 50 m / second. To this dispersion, 2 parts of latex B-1 is added based on the solid content, and only the planetary mixer is rotated at a peripheral speed of 0.25 m / second and mixed for 30 minutes to obtain a slurry composition for negative electrode having a solid content concentration of 54.7%. I got a thing. The average particle diameter of the electrode active material in this slurry composition was 25.7 μm. The peel strength of the negative electrode produced using this slurry composition was 6 g / cm, and Ra was 2.5 μm.

[Comparative Example 3]
A planetary mixer with a disperser is charged with 100 parts of artificial graphite having an average particle diameter of 25.5 μm, 3.9 parts of acetylene black, 31 parts of a selegen WSC 2.5% aqueous solution and 2 parts of latex B-1 on a solid basis. Only the mixer was rotated at a peripheral speed of 0.3 m / sec and kneaded for 60 minutes at a solid content of 68%. Thereafter, water was added to obtain a solid concentration of 55%, and a dispersion treatment was carried out for 20 minutes using a planetary mixer with a peripheral speed of 0.3 m / second and a disper with a peripheral speed of 50 m / second. Further, only the planetary mixer was rotated at a peripheral speed of 0.25 m / sec and mixed for 30 minutes to obtain a slurry composition for negative electrode having a solid content concentration of 55%. The average particle diameter of the electrode active material in this slurry composition was 35.0 μm. The peel strength of the positive electrode produced using this slurry composition was 4 g / cm, and Ra was 3.5 μm.

  As apparent from the above, when the slurry composition obtained by the production method of the present invention was used, electrodes having excellent surface smoothness and large binding force could be obtained (Examples 1 to 3). In contrast, an electrode manufactured using PTFE as a binder (Comparative Example 1) and an electrode manufactured using a slurry composition obtained by mixing all components at once (Comparative Examples 2 and 3) Was also inferior in surface smoothness and binding properties.

Claims (5)

A step (I) of kneading a water-soluble polymer, an electrode active material, a conductivity imparting material, and water to obtain a kneaded material in a funicular state, and the kneaded material and an acrylate system having a glass transition temperature of 20 ° C. or less The manufacturing method of the slurry composition for lithium ion secondary battery electrodes which has process (II) which mixes with the aqueous dispersion liquid of a polymer. Step (I) is a step (I-1) of mixing a water-soluble polymer, a conductivity-imparting material, and water to obtain a conductivity-imparting material dispersion, and adding an electrode active material to the conductivity-imparting material dispersion The manufacturing method of Claim 1 which has the process (I-2) knead | mixed. Step (II) is a step (II-1) in which the kneaded material is diluted and then dispersed with a disperser having a peripheral speed of 0.5 to 200 m / sec, and the obtained dispersion and water of the acrylate polymer are used. The manufacturing method of Claim 1 or 2 which has the process (II-2) which mixes a dispersion liquid. The manufacturing method according to claim 3, wherein the mixing is performed at a peripheral speed of less than 0.5 m / sec in the step (II-2). The production method according to claim 1, wherein the average particle diameter of the electrode active material in the slurry composition for a lithium ion secondary battery electrode is 1.3 times or less of the primary particle diameter.