WO2019235531A1 - Method for producing electrode active material particle aggregates and method for producing electrode - Google Patents

Abstract

[Problem] To provide a method for producing electrode active material particle aggregates which have high fluidity and are suitable for planarization. [Solution] A method for producing electrode active material particle aggregates which contain (a) electrode active material particles, (b) a conductive assistant and (c) an adhesive. This method for producing electrode active material particle aggregates is characterized by comprising: a first mixing step wherein the electrode active material particles (a) and the conductive assistant (b) are dry-mixed, thereby obtaining a mixture; a second mixing step wherein the adhesive (c) is added, in the form of a solution, to the mixture obtained in the first mixing step, while stirring the mixture, in an amount of 0.01-10% by mass relative to the total mass of the electrode active material particles (a), thereby obtaining a mixture; and a stirring step wherein the mixture obtained in the second mixing step is stirred.

Description

Method for producing electrode active material particle aggregate, and method for producing electrode

The present invention relates to a method for producing an electrode active material particle aggregate and a method for producing an electrode.

In recent years, reduction of carbon dioxide emissions has been strongly desired for environmental protection. In the automobile industry, there are high expectations for reducing carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and we are eager to develop secondary batteries for motor drives that hold the key to their practical application. Has been done. As a secondary battery, attention is focused on a lithium ion secondary battery that can achieve a high energy density and a high output density.

Patent Document 1 describes a method for producing granulated particles for electrochemical elements, which can be used for the production of lithium ion secondary batteries.

International Publication No. 2015/029829

In Patent Document 1, a particulate binder dispersion and an electrode active material are mixed to obtain a mixture, and the resulting mixture is stirred with a stirring blade. Obtaining particles is described. This method is a method for producing granulated particles called pulverization granulation, and examples of the particulate binder dispersion used in this production method include those in which a particulate binder such as latex is dispersed in water. It has been.

Here, as a method for manufacturing an electrode of a lithium ion secondary battery, granulated particles containing an electrode active material are supplied onto a sheet-like member such as a current collector, and are flattened using a squeegee or the like to form an electrode active material layer A method of forming is known.

When the granulated particles obtained by the method described in Patent Document 1 are used as the granulated particles used in such a method, since the fluidity of the granulated particles is low, flattening (slicing) with a squeegee In this case, the surface of the electrode active material layer may be roughened due to the granulated particles being caught. Also, when flattening with a squeegee, most of the granulated particles tend to be caught and carried by the squeegee, making it difficult to flatten the electrode active material layer to the target thickness. It was.

Based on the above situation, an object of the present invention is to provide a method for producing an electrode active material particle aggregate that has high fluidity and is suitable for flattening. Another object of the present invention is to provide a method for producing an electrode using the electrode active material particle aggregate obtained by the above production method.

The inventors of the present invention have come up with the present invention as a result of intensive studies to solve the above problems. That is, this invention is a manufacturing method of the electrode active material particle aggregate containing an electrode active material particle (a), a conductive support agent (b), and an adhesive (c), Comprising: Said electrode active material particle (a) and A first mixing step in which the conductive auxiliary agent (b) is dry-mixed to obtain a mixture, and the mixture obtained in the first mixing step is stirred to a total mass of the electrode active material particles (a). A second mixing step of adding 0.01 to 10% by mass of the pressure-sensitive adhesive (c) in the form of a solution to obtain a mixture, and a stirring step of stirring the mixture obtained in the second mixing step. A method for producing an electrode active material particle aggregate, comprising: an application step of coating the electrode active material particle aggregate obtained by the method for producing an electrode active material particle aggregate of the present invention on a substrate; It is related with the manufacturing method of the electrode characterized by these.

FIG. 1 is a perspective view schematically showing an example of a mixer that can be preferably used in the method for producing an electrode active material particle aggregate of the present invention.

Hereinafter, the present invention will be described in detail.
Note that in this specification, a lithium ion battery includes a lithium ion secondary battery.

The method for producing an electrode active material particle aggregate according to the present invention is a method for producing an electrode active material particle aggregate containing electrode active material particles (a), a conductive additive (b) and an adhesive (c), A first mixing step in which electrode active material particles (a) and the conductive auxiliary agent (b) are dry-mixed to obtain a mixture, and the mixture obtained in the first mixing step is stirred under the above electrode active material A second mixing step in which 0.01 to 10% by mass of the pressure-sensitive adhesive (c) is added in the form of a solution to the total mass of the particles (a) to obtain a mixture, and the mixture obtained in the second mixing step And a stirring step of stirring.

According to the method for producing an electrode active material particle aggregate of the present invention, an electrode active material particle aggregate having high fluidity and suitable for flattening can be obtained. Such an electrode active material particle aggregate having high fluidity can be suitably used in a method for producing an electrode including a coating step of coating the electrode active material particle aggregate on a substrate.

First, an electrode active material particle aggregate produced in the method for producing an electrode active material particle aggregate of the present invention and materials constituting the electrode active material particle aggregate will be described.

The electrode active material particle aggregate is an aggregate formed by further aggregating electrode active material particles with an adhesive. In this form, the aggregated particles expand / contract according to the expansion / contraction of the electrode active material particles accompanying charge / discharge. It is considered that the aggregated particles have a void that can absorb the increased volume of the electrode active material particles therein, thereby making it easier to suppress self-destruction of the electrode active material particles. The electrode active material particles forming the aggregate of the present invention may be primary particles or secondary particles aggregated by the adhesion force of the primary particles.

In the electrode active material particle aggregate, the electrode active material particles (a) and the electrode active material particles (a) and the conductive auxiliary agent (b) are bonded with a pressure-sensitive adhesive. Aggregated particles are reversibly bound to adjacent aggregated particles. Therefore, even if the primary particles expand and contract, the volume change can be easily absorbed, so that not only the electrode active material particles can be prevented from self-destructing, but also the electrode active material particle aggregates can be prevented from collapsing. be able to. Furthermore, since the primary particles are self-destructed due to expansion / contraction, the self-destructed electrode active material particles are not separated and are not easily isolated electrically because they are adhered by an adhesive.

The electrode active material particle aggregate includes electrode active material particles (a), a conductive additive (b), and an adhesive (c). The electrode active material particle aggregate is an aggregate of particles in which a plurality of electrode active material particles (a) and a conductive auxiliary agent (b) are combined to form a single body via an adhesive (c). Hereinafter, the electrode active material particles (a), the conductive assistant (b), and the pressure-sensitive adhesive (c) will be described.

The electrode active material particles (a) may be positive electrode active material particles or negative electrode active material particles. As the positive electrode active material, a composite oxide of lithium and a transition metal (a composite oxide having one kind of transition metal (such as LiCoO ₂ , LiNiO ₂ , LiAlMnO ₄ , LiMnO _2, and LiMn ₂ O ₄ ), a transition metal element is used. Two kinds of complex oxides (for example, LiFeMnO ₄ , LiNi _1-x Co _x O ₂ , LiMn _1-y Co _y O ₂ , LiNi _1/3 Co _1/3 Al _1/3 O ₂ and LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) and a composite oxide having three or more metal elements [for example, LiM _a M ′ _b M ″ _c O ₂ (M, M ′, and M ″ are different transition metal elements, respectively) , and the meet a + b + c = 1. for example _{LiNi 1/3 Mn 1/3 Co 1/3 O 2} ) , etc.] or the like}, lithium-containing transition metal phosphate (e.g. LiFePO _4, LiCo O _4, LiMnPO ₄ and LiNiPO _4), transition metal oxides (e.g., MnO ₂ and _V 2 _O 5), transition metal sulfides (e.g., MoS ₂ and TiS ₂₎ and the conductive polymer (such as polyaniline, polypyrrole, polythiophene, Polyacetylene, poly-p-phenylene, and polyvinylcarbazole), and the like may be used in combination. The lithium-containing transition metal phosphate may be one in which a part of the transition metal site is substituted with another transition metal.

The volume average particle diameter of the positive electrode active material particles is preferably 0.01 to 100 μm, more preferably 0.1 to 35 μm, and further preferably 2 to 30 μm, from the viewpoint of the electric characteristics of the battery. preferable.

Examples of the negative electrode active material include carbon-based materials [graphite, non-graphitizable carbon (hard carbon), amorphous carbon, resin fired bodies (for example, those obtained by firing and carbonizing phenol resin, furan resin, etc.), cokes (for example, Pitch coke, needle coke, petroleum coke, etc.) and carbon fiber, etc.], silicon-based materials [silicon, silicon oxide (SiOx), silicon-carbon composites (the surface of carbon particles coated with silicon and / or silicon carbide, The surface of silicon particles or silicon oxide particles coated with carbon and / or silicon carbide and silicon carbide) and silicon alloys (silicon-aluminum alloy, silicon-lithium alloy, silicon-nickel alloy, silicon-iron alloy, silicon- Titanium alloys, silicon-manganese alloys, silicon-copper alloys, silicon-tin alloys, etc.)], conductive polymers (eg polyacetylene and poly Rolls, etc.), metals (tin, aluminum, zirconium, titanium, etc.), metal oxides (titanium oxide and lithium / titanium oxide, etc.) and metal alloys (eg lithium-tin alloys, lithium-aluminum alloys and lithium-aluminum) And a mixture of these with a carbon-based material.

Among the negative electrode active materials described above, those that do not contain lithium or lithium ions may be subjected to a pre-doping treatment in which lithium or lithium ions are included in part or all of the negative electrode active material in advance.

Among these, from the viewpoint of battery capacity and the like, a carbon-based material, a silicon-based material, and a mixture thereof are preferable. As the carbon-based material, graphite, non-graphitizable carbon, and amorphous carbon are more preferable. Further, silicon oxide and silicon-carbon composite are more preferable.

The volume average particle diameter of the negative electrode active material particles is preferably from 0.01 to 100 μm, more preferably from 0.1 to 20 μm, and even more preferably from 2 to 10 μm, from the viewpoint of the electric characteristics of the battery.

In this specification, the volume average particle diameters of the positive electrode active material particles and the negative electrode active material particles are integrated values in the particle size distribution on the volume basis determined by the microtrack method and the laser diffraction / scattering method described in JIS Z 8825: 2013. Mean particle size (Dv50) at 50%. The microtrack method is a method for obtaining a particle size distribution using scattered light obtained by irradiating particles with laser light. In addition, the Nikkiso Co., Ltd. microtrack etc. can be used for the measurement of a volume average particle diameter.

The electrode active material may be a coated active material in which at least a part of its surface is coated with a coating layer containing a polymer compound. When the periphery of the electrode active material is covered with a coating layer, it is preferable in that the volume change of the electrode can be further eased and the expansion of the electrode can be suppressed.

Note that a coated active material when a positive electrode active material is used as the electrode active material is referred to as a coated positive electrode active material, and a coated active material layer is also referred to as a coated positive electrode active material layer. A coated active material when a negative electrode active material is used as the electrode active material is referred to as a coated negative electrode active material, and a coated active material layer is also referred to as a coated negative electrode active material layer.

As the coating resin constituting the coating layer, those described as a resin for coating a non-aqueous secondary battery active material in Japanese Patent Application Laid-Open No. 2017-054703 can be suitably used. The coated electrode active material particles can be obtained by mixing the coating resin and the electrode active material particles by the method described in 1. above. In addition, a conductive material may further be included in the coating layer as necessary, and the same material as the conductive additive (b) can be suitably used.

However, while the conductive material is included in the coating layer constituting a part of the coated electrode active material, the conductive auxiliary agent (b) can be clearly distinguished in that it is not included in the coating layer.

The conductive auxiliary agent (b) is selected from conductive materials.

Specifically, metal [nickel, aluminum, stainless steel (SUS), silver, copper, titanium, etc.], carbon [graphite and carbon black (acetylene black, ketjen black (registered trademark), furnace black, channel black, thermal lamp) Black) and the like], and mixtures thereof, but are not limited thereto.
These conductive assistants may be used alone or in combination of two or more. Moreover, you may use the alloy of the said metal. From the viewpoint of electrical stability, aluminum, stainless steel, carbon, silver, copper, titanium and a mixture thereof are preferable, silver, aluminum, stainless steel and carbon are more preferable, and carbon is more preferable. Moreover, as these conductive support agents, the thing which coated the electroconductive material (metal thing among the materials of the above-mentioned conductive support agent) by plating etc. around the particle-type ceramic material or the resin material may be used.

The shape (form) of the conductive auxiliary agent is not particularly limited, and may be particulate or fibrous, and carbon nanotubes, carbon nanofibers, conductive fibers, or the like can also be used.

The average particle diameter of the particulate conductive additive is not particularly limited, but is preferably 0.01 to 10 μm, more preferably 0.02 to 5 μm from the viewpoint of the electric characteristics of the battery. Preferably, it is 0.03 to 1 μm. In the present specification, the “particle diameter of the conductive additive” means the maximum distance L among the distances between any two points on the contour line of the conductive additive. The value of the “average particle diameter of the conductive auxiliary agent” is several to several in an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM) according to the method described in JIS Z 8827-1: 2008. The value calculated as the average value of the particle diameter of the conductive additive observed in the ten visual fields shall be adopted.

Examples of conductive fibers include carbon fibers such as PAN-based carbon fibers and pitch-based carbon fibers, conductive fibers obtained by uniformly dispersing highly conductive metal and graphite in synthetic fibers, and metals such as stainless steel. Examples thereof include fiberized metal fibers, conductive fibers in which the surface of organic fiber is coated with metal, and conductive fibers in which the surface of organic fiber is coated with a resin containing a conductive substance. Among these conductive fibers, carbon fibers are preferable. A polypropylene resin in which graphene is kneaded is also preferable. When the conductive auxiliary agent is a conductive fiber, the average fiber diameter is preferably 0.1 to 20 μm.

The pressure sensitive adhesive (c) exhibits adhesiveness to the surface of the electrode active material particles (a). Therefore, the electrode active material particles can be granulated by mixing and stirring the electrode active material particles (a) and the pressure-sensitive adhesive (c), and electrode active material particle aggregates can be obtained.

The pressure-sensitive adhesive (c) is sticky at room temperature and has a property of adhering to an adherend with light pressure, as defined in JIS K6800: 2006 “Adhesive / Adhesion Term”.

The pressure-sensitive adhesive (c) is used in the form of a solution obtained by dissolving the pressure-sensitive adhesive (c) in a solvent in the method for producing an electrode active material particle aggregate of the present invention.

As the pressure-sensitive adhesive (c), the pressure-sensitive adhesive composition described in JP-A No. 2004-143420 and the acrylic pressure-sensitive adhesive composition described in JP-A No. 2000-239633 can be used. It is preferable to include a polymer containing at least one monomer selected from the group consisting of 2-ethylhexyl (meth) acrylate, (meth) acrylic acid, and butyl (meth) acrylate.

In this specification, (meth) acrylic acid indicates acrylic acid and / or methacrylic acid, and (meth) acrylate indicates acrylate and / or methacrylate.

In particular, the pressure-sensitive adhesive (c) preferably contains a copolymer containing at least 2-ethylhexyl (meth) acrylate and (meth) acrylic acid as constituent monomers. In this case, the total mass of 2-ethylhexyl (meth) acrylate and (meth) acrylic acid in the constituent monomer of the copolymer is 10% by mass with respect to the total mass of the constituent monomer of the copolymer. The above is preferable. Further, the total mass of 2-ethylhexyl (meth) acrylate and (meth) acrylic acid in the constituent monomer of the copolymer is 65% by mass or less based on the total mass of the constituent monomers of the copolymer. It is preferable. When the total mass of 2-ethylhexyl (meth) acrylate and (meth) acrylic acid in the constituent monomer of the copolymer is within this range, the strength of the electrode active material particle aggregate is favorable, which is preferable. The constituent monomer other than the above is not particularly limited, and examples thereof include vinyl acetate and 2-hydroxyethyl (meth) acrylate.

As the pressure-sensitive adhesive (c), only one type may be used, or two or more types may be used in combination. Preferably, the ratio of the copolymer containing 2-ethylhexyl (meth) acrylate and (meth) acrylic acid as constituent monomers to the total amount of the pressure-sensitive adhesive (c) used is 80% by mass or more. 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, and most preferably 100% by mass.

The preferable lower limit of the weight average molecular weight of the pressure-sensitive adhesive (c) is 10,000, more preferably 50,000, still more preferably 100,000, and the preferable upper limit is 1,000,000, more preferably 800,000, 500,000 is preferable, and 450,000 is particularly preferable. When using 2 or more types of adhesives, it is preferable that the weight average molecular weight of the at least 1 sort is the said range, and it is more preferable that all the weight average molecular weights are the said range.

The weight average molecular weight of the pressure-sensitive adhesive (c) can be determined by gel permeation chromatography (hereinafter abbreviated as GPC) measurement under the following conditions.

Equipment: “HLC-8120GPC” [manufactured by Tosoh Corporation]
Column: "TSKgel GMHXL" (2), "TSKgel Multipore HXL-M each connected" [all manufactured by Tosoh Corporation]
Sample solution: 0.25 mass% tetrahydrofuran solution Solution injection amount: 10 μL
Flow rate: 0.6 mL / min Measurement temperature: 40 ° C
Detector: Refractive index detector Reference material: Standard polystyrene [manufactured by Tosoh Corporation].

The pressure-sensitive adhesive (c) is a known polymerization initiator {azo initiator [2,2′-azobis (2-methylpropionitrile), 2,2′-azobis (2-methylbutyronitrile), 2, 2′-azobis (2,4-dimethylvaleronitrile, etc.)], peroxide-based initiators (benzoyl peroxide, di-t-butyl peroxide, lauryl peroxide, etc.), etc.} Solution polymerization).

The amount of the polymerization initiator used is preferably from 0.01 to 5% by mass, more preferably from 0.05 to 2% by mass, and even more preferably from the viewpoint of adjusting the molecular weight to a preferable range. The polymerization temperature and polymerization time are adjusted according to the type of the polymerization initiator, etc., but the polymerization temperature is preferably −5 to 150 ° C. (more preferably 30 to 120 ° C.), and the reaction time is preferably 0.1 to 50 hours (more preferably 2 to 24 hours).

Examples of the solvent used for the polymerization include esters (having 2 to 8 carbon atoms such as ethyl acetate and butyl acetate), alcohols (having 1 to 8 carbon atoms such as methanol, ethanol and octanol), hydrocarbons (having 4 to 8 carbon atoms). For example, n-butane, cyclohexane and toluene) and ketones (having 3 to 9 carbon atoms, for example, methyl ethyl ketone). From the viewpoint of adjusting the molecular weight to a preferred range, the amount used is based on the total mass of the monomers. Preferably, it is 5 to 900% by mass, more preferably 10 to 400% by mass, particularly preferably 30 to 300% by mass, and the monomer concentration is preferably 10 to 95% by mass, more preferably 20 to 90% by mass, Particularly preferred is 30 to 80% by mass.

In the polymerization, known chain transfer agents such as mercapto compounds (such as dodecyl mercaptan and n-butyl mercaptan) and / or halogenated hydrocarbons (such as carbon tetrachloride, carbon tetrabromide and benzyl chloride) can be used. .

As the pressure-sensitive adhesive (c), a commercially available pressure-sensitive adhesive [polysic series (manufactured by Sanyo Chemical Industries, Ltd.), etc.] may be used.

The pressure-sensitive adhesive (c) is a known dry-type binder for lithium ion battery electrodes (starch, polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose, polyvinylpyrrolidone, tetrafluoroethylene, styrene-butadiene rubber, polyethylene, polypropylene and styrene. -A material different from butadiene copolymer or the like).

In the electrode active material particle aggregate obtained by the method for producing an electrode active material particle aggregate of the present invention, the electrode active material particle aggregate is integrated with the electrode active material particle and the conductive additive. Even when deformed, the electrode active material particles and the conductive additive can move freely to some extent following the deformation. Therefore, even when the electrode active material particles expand and contract and the electrode active material particle aggregates are deformed, it is possible to suppress the electrode active material particles and the conductive auxiliary agent from dropping from the electrode active material particle aggregates. it can.

Furthermore, even if the electrode active material particles are self-destructed due to expansion / contraction, they are not easily isolated electrically because they are bundled with the adhesive.

The solvent-dried electrode binder is a material that is dried and solidified by volatilizing the solvent component to firmly fix the electrode active material particles to each other and the electrode active material particles and the current collector. The surface is not sticky. On the other hand, the pressure-sensitive adhesive is a material having a property of having adhesiveness even when the solvent component is volatilized and dried. That is, in the method for producing an electrode active material particle aggregate and the method for producing an electrode of the present invention, it is preferable not to use the solvent-drying type electrode binder.

The electrode active material particle aggregate obtained by the method for producing an electrode active material particle aggregate of the present invention preferably has a volume average particle diameter of 20 to 350 μm.
In addition, this volume average particle diameter is a particle diameter as an aggregate.

In this specification, the volume average particle diameter of the electrode active material particle aggregate is an integrated value of 50% in the particle size distribution on the volume basis determined by the microtrack method and the laser diffraction / scattering method described in JIS Z 8825: 2013. Mean particle size (Dv50). The microtrack method is a method for obtaining a particle size distribution using scattered light obtained by irradiating particles with laser light. In addition, the Nikkiso Co., Ltd. microtrack etc. can be used for the measurement of a volume average particle diameter.

Then, each process of the manufacturing method of the electrode active material particle aggregate of this invention is demonstrated.

In the first mixing step, the electrode active material particles (a) and the conductive additive (b) are dry mixed to obtain a mixture.

The order of mixing in the first mixing step is not particularly limited, and the conductive additive (b) may be mixed with the electrode active material particles (a), and the electrode active material particles (a) may be mixed with the conductive auxiliary agent (b). You may mix. Mixing is performed by dry mixing to obtain a mixture of the electrode active material particles (a) and the conductive additive (b). Although the apparatus used for dry mixing is not particularly limited, a mixer described later can be preferably used. Preferred mixing conditions when using the mixer will also be described later.

In the second mixing step, the adhesive (c) is added in the form of a solution to the mixture obtained in the first mixing step under stirring.

Adhesive (c) is added in the form of a solution. The solution in the present specification means a state in which a component exhibiting adhesiveness contained in an adhesive is dissolved in a solvent, and has a transparent appearance. That is, it is different from an opaque suspension in which fine particles are dispersed in a liquid, such as a latex binder.

The solution of the pressure-sensitive adhesive (c) can be obtained by dissolving the pressure-sensitive adhesive (c) in a solvent capable of dissolving the pressure-sensitive adhesive (c) by a known method. The concentration of the pressure-sensitive adhesive (c) in the solution is preferably 0.01 to 20% by mass, and more preferably 5 to 10% by mass.

When the concentration of the pressure-sensitive adhesive (c) in the solution is within the above range, the electrode active material particles (a), the conductive auxiliary agent (b) and the pressure-sensitive adhesive (c) can be uniformly mixed to improve the yield of the aggregate. Can be made.

The concentration of the pressure-sensitive adhesive (c) in the solution is measured as a ratio of the mass of evaporation residue remaining after evaporation of the solvent in the solution by heating (preferably 80 to 120 ° C.) as necessary. The

As a solvent for the solution of the pressure-sensitive adhesive (c), any solvent that can dissolve the pressure-sensitive adhesive (c) can be used without limitation, but ester solvents are preferable, and ethyl acetate is more preferable.

In the method for producing an electrode active material particle aggregate of the present invention, the first mixing step and the second mixing step are distinguished from each other in that the electrode active material particles (a), the conductive auxiliary agent (b), and the adhesive (c) This means that the order of mixing is important, and it is a feature of the present invention that the adhesive (c) is added later to the mixture of the electrode active material particles (a) and the conductive additive (b). Yes.

Conductive aid (b) after electrode active material particles (a), conductive additive (b) and pressure-sensitive adhesive (c) are mixed at once, or mixed with electrode active material particles (a) and pressure-sensitive adhesive (c). If the electrode active material particles (a) are added after mixing the conductive assistant (b) and the pressure sensitive adhesive (c), an electrode active material particle aggregate having high fluidity cannot be produced.

In the second mixing step, 0.01 to 10% by mass of the pressure-sensitive adhesive (c) is added in the form of a solution with respect to the total mass of the electrode active material particles (a).

When the added amount of the pressure-sensitive adhesive (c) is less than 0.01% by mass with respect to the total mass of the electrode active material particles (a), the amount of the pressure-sensitive adhesive (c) is too small and the electrode active material is hardly aggregated. The strength of the resulting aggregate is not sufficient.

Moreover, when the addition amount of an adhesive (c) exceeds 10 mass% with respect to the total mass of electrode active material particle (a), there is too much quantity of an adhesive (c) and an excess adhesive (c) will become an electrode. Since it coexists with the active material particle aggregate, the fluidity of the electrode active material particle aggregate becomes low.

Further, it is preferable to add 1 to 5% by mass, particularly 1 to 3% by mass of the adhesive (c) in the form of a solution with respect to the total mass of the electrode active material particles (a). This range is preferable because it is easier to achieve both the strength and fluidity of the electrode active material particle aggregate.

The addition amount of the pressure-sensitive adhesive (c) in this specification is an amount that can be determined by multiplying the blending amount of the solution and the concentration of the pressure-sensitive adhesive (c) in the solution. The amount added.

The amount of the pressure-sensitive adhesive (c) thus determined is set to 0.01 to 10% by mass with respect to the total mass of the electrode active material particles (a).

The addition of the pressure-sensitive adhesive (c) in the second mixing step is performed with stirring. Although the apparatus used for stirring is not specifically limited, The mixer mentioned later can be used conveniently. Preferred stirring conditions when using the mixer will also be described later.

In addition, the addition of the pressure-sensitive adhesive (c) in the second mixing step may be performed at a time or may be performed in divided portions. At this time, the first addition of the pressure-sensitive adhesive is defined as the start of the second mixing step.

In the stirring step, the mixture obtained in the second mixing step (a mixture of the electrode active material particles (a), the conductive additive (b), and the pressure-sensitive adhesive (c)) is stirred.

This stirring is preferably performed continuously with the second mixing step, and continuing the stirring as it is after adding the pressure-sensitive adhesive (c) under stirring in the second mixing step corresponds to the stirring step.

Stirring conditions in the stirring step are not particularly limited, and may be the same stirring conditions when adding the pressure-sensitive adhesive (c) under stirring in the second mixing step, or may be different stirring conditions. When setting it as different stirring conditions, it is equivalent to a stirring process to stir on the stirring conditions different from the stirring conditions at the time of adding an adhesive (c).

Although the apparatus used for stirring is not particularly limited, a mixer described later can be preferably used. Preferred stirring conditions when using the mixer will also be described later. By stirring in the stirring step, electrode active material particle aggregates are obtained.

Subsequently, a mixer that can be preferably used in the method for producing an electrode active material particle aggregate of the present invention will be described.

In the method for producing an electrode active material particle aggregate of the present invention, at least one of the dry mixing in the first mixing step, the stirring in the second mixing step, and the stirring in the stirring step contains the contents. A rotating container that rotates as it is, and a stirring blade that is disposed inward of the rotating container and deviated from the rotating center axis of the rotating container in parallel with the rotating center axis, and the rotating container and the stirring blade It is preferable to use a mixer that rotates and mixes the contents.

Examples of such mixers include the mixers described in JP2013-017923A, and examples of commercially available mixers include Eirich Intensive Mixer (manufactured by Eirich Japan).

FIG. 1 is a perspective view schematically showing an example of a mixer that can be preferably used in the method for producing an electrode active material particle aggregate of the present invention.

A mixer 1 shown in FIG. 1 includes a rotating container 4 that rotates while containing contents. The rotating container 4 rotates around a rotation center axis CL ₁ (hereinafter also referred to as center axis CL ₁ ). The central axis CL ₁ is preferably tilted with respect to the horizontal plane (indicated by line H in the figure). The mixer 1 includes a stirring blade 3 that rotates about a rotation center axis CL ₂ (hereinafter also referred to as a center axis CL ₂ ). The stirring blade 3 has a head portion 5 that is rotationally driven and a rod-like member 6 that is attached to the head portion 5 and extends to the vicinity of the bottom plate 7 of the rotating container 4. Although at least one rod-like member 6 is preferably provided, six are provided in the mixer shown in FIG. Stirring blades 3 are disposed eccentrically from the center axis line CL ₁ of the rotary vessel position. Stirring blade 3 is to be located at a position eccentric from the center axis line CL ₁ of the rotating container, the central axis CL ₂ of rotation of the stirring blade 3 means that does not coincide with the center axis line CL ₁ of the rotary vessel.

Head portion of the stirring blade 35 is rotated is parallel to the center axis CL ₁ of the rotary vessel. Then, it is parallelly arranged evenly angle and the same distance to the environment around the rod-like member 6 of the central axis CL ₂ the head portion 5. The shape of the rod-shaped member is not limited to a linear shape, and may be formed by bending into a predetermined shape. The cross-sectional shape of the rod-shaped member is preferably circular, but may be an ellipse, a polygon, or other predetermined shape.

The contents in the mixer 1 are agitated by rotating around the central axis CL ₁ of the rotating container 4 or rotating around the central axis CL ₂ of the stirring blade 3. If this is a mixer 1, the rotation about the center axis line CL ₁ of the rotating container 4, and it is preferable to perform the rotation about the center axis line CL ₂ of the agitating blades 3 at the same time. By performing these two types of rotation simultaneously, an electrode active material particle aggregate with higher fluidity can be obtained.

The rotation direction of the rotating container and the rotation direction of the stirring blade may be the same direction or the opposite direction. FIG. 1 shows an example in which the rotation direction of the rotating container (arrow B ₁ ) is clockwise and the rotation direction of the stirring blade (arrow B ₂ ) is also clockwise. When the rotating container and the stirring blade move in this way, the rod-shaped member moves in the circumferential direction in the rotating container, and the rod-shaped member can stir the mixture over a wide area in the rotating container.

In the method for producing an electrode active material particle aggregate of the present invention, the mixer can be used in any of the first mixing step, the second mixing step, and the stirring step.

It is also preferable to perform the first mixing step, the second mixing step, and the stirring step continuously using the same mixer.

Preferred stirring conditions in each step when using the mixer are as follows.

(1) Dry mixing conditions in the first mixing step Rotational conditions of the rotating container: low speed rotation reverse to the stirring blades (preferred peripheral speed is 1 to 3 m / s)
Stirring blade peripheral speed: 10-20m / s
Dry mixing time: 5 to 10 minutes (2) Stirring conditions when adding the pressure-sensitive adhesive (c) in the second mixing step Rotating condition of the rotating container: Low speed rotation reverse to the stirring blades (preferred peripheral speed is 1 to 3 m / S)
Stirring blade peripheral speed: 10-20m / s
Speed at which the pressure-sensitive adhesive is added: Speed at which the number of parts of the pressure-sensitive adhesive (c) added per minute to 100 parts of the electrode active material particles is 0.1 to 1 part. (3) Stirring conditions in the stirring step Reverse rotation with stirring blades and low speed rotation (preferred peripheral speed is 1 to 3 m / s)
Stirring blade peripheral speed: 20-30m / s
Stirring time: 15-25 minutes.

The electrode active material particle aggregate obtained through the stirring step may be subjected to a treatment such as drying as necessary.

Subsequently, an electrode manufacturing method of the present invention in which an electrode is manufactured using the electrode active material particle aggregate obtained by the electrode active material particle aggregate manufacturing method of the present invention will be described.

The method for producing an electrode of the present invention is characterized by including a coating step of coating the electrode active material particle aggregate obtained by the method for producing an electrode active material particle aggregate of the present invention on a substrate.

It is preferable to use a current collector as the base material used for manufacturing the electrode. The current collector is not particularly limited, but a known metal current collector and a resin current collector composed of a conductive material and a resin (described in JP 2012-150905 A) and the like are preferably used. Can be used.

The metal current collector is, for example, selected from the group consisting of copper, aluminum, titanium, nickel, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony and alloys containing one or more of these, and stainless steel alloys. These metal materials may be used in the form of a thin plate or a metal foil, and the above metal material is formed on the surface of the substrate by a technique such as sputtering, electrodeposition or coating. There may be.

The conductive material constituting the resin current collector is selected from materials having conductivity. Specifically, metal [nickel, aluminum, stainless steel (SUS), silver, copper, titanium, etc.], carbon [graphite and carbon black (acetylene black, ketjen black (registered trademark), furnace black, channel black, thermal lamp) Black) and the like], and mixtures thereof, but are not limited thereto.

These conductive materials may be used alone or in combination of two or more. Further, these alloys or metal oxides may be used. From the viewpoint of electrical stability, aluminum, stainless steel, carbon, silver, copper, titanium and a mixture thereof are preferable, silver, aluminum, stainless steel and carbon are more preferable, and carbon is more preferable. Moreover, as these electrically conductive materials, what coated the electroconductive material (metal thing among the above-mentioned electrically conductive materials) by plating etc. around the particulate ceramic material or the resin material may be used.

The resin constituting the resin current collector includes polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polycycloolefin (PCO), polyethylene terephthalate (PET), polyether nitrile (PEN), polytetra Fluoroethylene (PTFE), styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), epoxy resin, silicone resin or a mixture thereof Is mentioned.

From the viewpoint of electrical stability, polyethylene (PE), polypropylene (PP), polymethylpentene (PMP) and polycycloolefin (PCO) are preferable, and polyethylene (PE), polypropylene (PP) and polymethylpentene are more preferable. (PMP).

In the coating step, the electrode active material particle aggregate obtained by the method for producing the electrode active material particle aggregate of the present invention is coated on a substrate.

In the electrode of the present invention, the agglomerated particles are preferably not bound to each other, that is, the electrode active material layer obtained by applying the electrode active material particle agglomerates on the substrate may be non-bound. preferable. Here, the non-binding body means that the electrode active material particles constituting the electrode active material layer are not bonded to each other. The bond is irreversibly fixed to the electrode active material particles. Means that.

Since the electrode active material particle aggregate obtained by the method for producing an electrode active material particle aggregate of the present invention is formed by integrating the electrode active material particles and the conductive additive with an adhesive, an electrode including an adhesive is produced. In this case, the electrode active material layer is maintained as a non-binding body. When the electrode active material layer is a non-binding body, the electrode active material particle aggregate can freely move to some extent in the electrode active material layer. Therefore, even if expansion / contraction of the electrode active material particles occurs, the volume change can be absorbed by the electrode active material particles moving through the electrode active material particle aggregates. Peeling from the current collector can also be suppressed.

Furthermore, even if the electrode active material particles are self-destructed due to expansion / contraction, they are collected by the pressure-sensitive adhesive (c), so that they do not fall off from the electrode active material layer and become electrically isolated.

In addition, when applying the electrode active material particle aggregate on the substrate, the electrode active material layer is not bound by not using a known electrode binder (a known lithium ion battery electrode binder which is a solvent dry type) in combination. It can be a body.

In order to form an electrode active material layer using the above known electrode binder together, it is necessary to perform a drying step after applying the electrode active material particle aggregate on the substrate. Since the electrode active material particle aggregate obtained by the method for producing the material particle aggregate contains an adhesive, the electrode active material particle aggregate is in powder form without using the above-mentioned known electrode binder. The electrode active material layer can be formed without performing a drying step, for example, by coating on a material and compressing. When an electrode active material layer is formed without performing a drying step, shrinkage and cracking of the electrode active material layer due to heating are unlikely to occur, the electrode active material layer can be thickened, and a high-capacity battery can be obtained. This is preferable.

Application of the electrode active material particle aggregate on the base material is a method of dispersing the electrode active material particle aggregate in the electrolytic solution and a non-aqueous solvent contained in the electrolytic solution, and applying using a known coating apparatus, and For example, a method of applying the electrode active material particle aggregate as a powder on a substrate can be used.

It is preferable to perform a thickness adjusting step for adjusting the thickness of the electrode active material particle aggregate applied on the substrate. The thickness adjusting step is preferably a flattening step using a squeegee. Moreover, it is also preferable to be a step of adjusting the thickness of the electrode active material particle aggregate by applying vibration to the electrode active material particle aggregate applied to the substrate. In addition, the electrode active material particle aggregate is applied to the base material while aligning the thickness by quantitatively supplying the electrode active material particle aggregate to the moving base material, thereby simultaneously performing the coating process and the thickness adjusting process. It may be a form that is performed.

Since the electrode active material particle aggregate obtained by the method for producing an electrode active material particle aggregate of the present invention has high fluidity, the electrode active material particle aggregate can be appropriately spread on the substrate when applied to the substrate. And thickness can be easily adjusted with a thickness adjustment process.

Subsequently, it is preferable to perform a pressurizing step of applying pressure on the electrode active material particle aggregate that has been applied on the substrate and subjected to a thickness adjusting step as necessary. The pressurizing step can be performed using roll rolling or the like, whereby an electrode in which electrode active material particle aggregates are uniformly provided at a predetermined position on the substrate with a predetermined basis weight can be obtained. The force applied when pressurizing by roll rolling is preferably 4.9 kN to 295 kN. For example, the linear pressure when rolling using a roll having a diameter of 250 mm × length of 250 mm is 19.6 kN / m to 1176.5 kN / m is preferable.

The electrode obtained in this manner can be made into a battery by a treatment such as being housed in a battery outer package in combination with an electrolytic solution, a separator, and a counter electrode.

Next, the present invention will be specifically described by way of examples. However, the present invention is not limited to the examples without departing from the gist of the present invention. Unless otherwise specified, “part” means “part by mass” and “%” means “% by mass”.

Production Example 1
(Manufacture of adhesives)
A 4-neck Kolben equipped with a stirrer, thermometer, reflux condenser, dropping funnel and nitrogen gas inlet tube was charged with 5.0 parts of vinyl acetate, 23.7 parts of 2-ethylhexyl acrylate, and 185.5 parts of ethyl acetate 75 The temperature was raised to ° C. 11.1 parts vinyl acetate, 21.0 parts 2-ethylhexyl acrylate, 28.1 parts 2-hydroxyethyl methacrylate, 11.1 parts acrylic acid and 2,2′-azobis (2,4-dimethylvaleronitrile) 200 parts of the monomer mixture obtained by mixing 200 parts and 2,2′-azobis (2-methylbutyronitrile) 0.200 parts was heated to 75 ° C., and nitrogen was introduced into the four-necked Kolben. While blowing, radical polymerization was carried out by continuously dropping with a dropping funnel over 4 hours. After completion of the dropwise addition, a solution prepared by dissolving 0.800 part of 2,2′-azobis (2,4-dimethylvaleronitrile) in 12.4 parts of ethyl acetate was used to start polymerization using a dropping funnel after the start of polymerization. Added continuously over time. Furthermore, after the polymerization was continued for 2 hours at the boiling point, while maintaining the temperature, the inside of the Kolben was gradually reduced with a vacuum pump, and the ethyl acetate was distilled off by maintaining the temperature until no ethyl acetate flow was observed. A polymer was obtained. When the molecular weight of the obtained polymer was measured by GPC, the weight average molecular weight (hereinafter abbreviated as Mw) was 420,000. The measurement conditions for Mw are as described above.

(Example 1)
The following 1st mixing process, 2nd mixing process, and stirring process were performed, and the electrode active material particle aggregate (1) concerning Example 1 was manufactured.

(First mixing step)
A mixer having the shape shown in FIG. 1 [manufactured by Japan Eirich Co., Ltd., Eirich Intensive Mixer, Model EL-1] was prepared, and LiNi _0.8 Co _0.15 Al _0.05 having a number average particle size of 5 μm was placed in the rotating container of the mixer. 95 parts of O ₂ particles [Toda Kogyo Co., Ltd. (hereinafter referred to as NCA)] and 2 parts of carbon nanofiber [Showa Denko Co., Ltd., carbon nanotube VGCF (hereinafter referred to as CNF)] as a conductive auxiliary agent are added. In the first mixing step, the mixture was obtained by mixing at the rotation speed of the rotating container (also referred to as a mixing pan) at 85 rpm (inner diameter of the mixing pan). : 400 mm, peripheral speed 1.8 m / s), the peripheral speed of the stirring blade (also called rotor) is set to 17 m / s, and the dry mixing time is 7 minutes. Was Tsu.

(Second mixing step)
30 parts of an ethyl acetate solution (adhesive concentration: 10% by mass) of an adhesive obtained by dissolving 3 parts of the adhesive produced in Production Example 1 in 27 parts of ethyl acetate (ethyl acetate solution (1) of adhesive) The second mixing step was performed by adding the mixture in the mixing pan of the mixer after performing the first mixing step into three parts in the mixing pan after stirring in the mixer at intervals of 5 minutes. Mixing in the second mixing step is performed by setting the rotation speed of the mixing pan to 85 rpm in the direction opposite to that of the stirring blade, the peripheral speed of the rotor to 17 m / s, and the mixing time with the initial adhesive solution being charged as 0 minutes. This was done for 12 minutes.

(Stirring process)
After the end of the second mixing step, the rotation speed of the mixing pan is set to 85 rpm in the direction opposite to that of the stirring blade, and the circumferential speed of the rotor is set to 24 m / s, so that the ethyl acetate naturally evaporates during mixing. The electrode active material particle aggregate (1) according to Example 1 was manufactured by mixing for 20 minutes with the suction port opened and performing a stirring step.

(Example 2)
Implemented except that the NCA was changed to 98 parts in the first mixing step of Example 1, and the amount of the ethyl acetate solution (1) in the adhesive was changed to 0.098 parts in the second mixing step of Example 1. In the same manner as in Example 1, an electrode active material particle aggregate (2) according to Example 2 was produced.

(Example 3)
Except that the NCA was changed to 88.2 parts in the first mixing step of Example 1, and the input amount of the ethyl acetate solution (1) of the adhesive was changed to 88.2 parts in the second mixing step of Example 1. Produced an electrode active material particle aggregate (3) according to Example 3 in the same manner as in Example 1.

Example 4
In the second mixing step of Example 1, the pressure-sensitive adhesive concentration of the ethyl acetate solution of the pressure-sensitive adhesive was changed to 20% by mass (the pressure-sensitive adhesive ethyl acetate solution (2)), and the pressure-sensitive adhesive ethyl acetate solution (2) was added. An electrode active material particle aggregate (4) according to Example 4 was produced in the same manner as in Example 1 except that the amount was changed to 15 parts.

(Example 5)
In the second mixing step of Example 1, the pressure-sensitive adhesive concentration of the ethyl acetate solution of the pressure-sensitive adhesive was changed to 5 mass% (ethyl acetate solution of the pressure-sensitive adhesive (3)), and further the ethyl acetate solution of the pressure-sensitive adhesive (3) was added. An electrode active material particle aggregate (5) according to Example 5 was produced in the same manner as in Example 1 except that the amount was changed to 60 parts.

(Example 6)
In the second mixing step of Example 1, the pressure-sensitive adhesive concentration of the ethyl acetate solution of the pressure-sensitive adhesive was changed to 0.01 mass% (pressure-sensitive adhesive ethyl acetate solution (4)), and the pressure-sensitive adhesive ethyl acetate solution (4). An electrode active material particle agglomerate (6) according to Example 6 was produced in the same manner as in Example 1 except that the input amount of was changed to 30000 parts.

(Example 7)
In the second mixing step of Example 1, the same procedure as in Example 1 was performed except that 30 parts of the ethyl acetate solution (1) (adhesive concentration: 10% by mass) of the adhesive was added all at once. Thus, an electrode active material particle aggregate (7) according to Example 7 was produced.

(Example 8)
Example 1 The same as Example 1 except that 95 parts of NCA were changed to 95 parts of hard carbon [manufactured by Kureha Corporation, Carbotron PS (F) (hereinafter referred to as HC)] in the first mixing step of Example 1. An electrode active material particle aggregate (8) according to No. 8 was produced.

Example 9
The following 1st mixing process, 2nd mixing process, and stirring process were performed, and the electrode active material particle aggregate (9) concerning Example 9 was manufactured.

(First mixing step)
A mixer [Nippon Coke Co., Ltd., FM mixer, type FM 10C / I] having two differently shaped stirring blades vertically stacked at the center of the bottom of the mixing vessel was prepared. 2 parts of carbon nanofibers were added and dry mixing as the first mixing step was performed to obtain a mixture. Mixing in the first mixing step was performed by setting the peripheral speed of the stirring blade to 17 m / s and the dry mixing time as 10 minutes.

(Second mixing step)
30 parts of an ethyl acetate solution (adhesive concentration: 10% by mass) of an adhesive obtained by dissolving 3 parts of the adhesive produced in Production Example 1 in 27 parts of ethyl acetate (ethyl acetate solution (1) of adhesive) The second mixing step was performed by adding the mixture in the mixer container after the first mixing step into three in 3 minutes and under the stirring of the mixer at intervals of 5 minutes. Mixing in the second mixing step was performed by setting the peripheral speed of the stirring blade to 17 m / s, setting the initial pressure-sensitive adhesive solution to 0 minutes, and setting the mixing time to 12 minutes.

(Stirring process)
After the end of the second mixing step, the peripheral speed of the stirring blade was set at 24 m / s, and the stirring step was performed by mixing for 20 minutes to produce the electrode active material particle aggregate (9) according to Example 9. .

(Comparative Example 1)
100 parts of NCA and 1 part of carbon nanofibers were added to the mixer used in Example 9, and dry blended for 10 minutes. Next, a 40% by mass aqueous dispersion of a styrene-butadiene copolymer (SBR) as a binder [Latex BM-400B, manufactured by Nippon Zeon Co., Ltd.] was bonded to the mixture of NCA and conductive additive in the mixer. Spraying was performed in such an amount that the adsorbent was 1 part in terms of solid content. After adding the aqueous dispersion of the binder, the kneading step was performed for 3 minutes with the peripheral speed of the stirring blade being 17 m / s. Thereafter, the stirring blade was further moved at a peripheral speed of 24 m / s for 2 minutes to perform a crushing process, and then dried under reduced pressure at 50 ° C. for 30 minutes to produce a comparative electrode active material particle aggregate (H1).

(Comparative Example 2)
The following mixing operation was performed to produce a comparative electrode active material particle aggregate (H2) according to Comparative Example 2.

(First mixing step)
Prepare the same mixer as used in Example 1, and mix 95 parts of NCA in the mixing pan of the mixer with the rotating speed of the mixing pan set to 85 rpm in the direction opposite to the stirring blades and the peripheral speed of the rotor set to 24 m / s. 2 parts of carbon nanofibers and 30 parts of an ethyl acetate solution (1) of the same adhesive as used in Example 1 were added at a time, and stirring was continued for 30 minutes after the addition.

Fluidity of electrode active material particle aggregates (1) to (9) obtained in Examples 1 to 9 and comparative electrode active material particle aggregates (H1) to (H2) obtained in Comparative Examples 1 and 2 Were evaluated in the following items, and the results are shown in Table 1 together with the production conditions of the electrode active material particle aggregates.

<1. Fluidity when creating a powder layer>
Evaluation of powder fluidity when the surface of the powder layer made of the electrode active material particle aggregates was scraped with a flat plate was performed by the following method.

(1) Grinding the surface of the powder layer 5 g of electrode on a 100 μm thick PP resin film set on an automatic applicator for applicators [Desktop Test Coater (model: EGPI-1210) manufactured by Eager Corporation] The active material particle aggregate is placed in a mountain shape, and a film applicator having a thickness of 600 μm is translated on the mountain of the electrode active material particle aggregate at a constant speed of 10 mm / s, and the surface of the mountain is rubbed off. It was. In addition, after performing scraping, when linear scratches were observed on the surface, the scraping operation was repeated until a surface having no scratch was obtained.

(2) Average thickness of powder layer The thickness of the powder layer produced on the PP resin film (the height from the surface of the PP resin film to the surface of the powder layer) is measured by Keyence's three-dimensional shape measuring instrument VR. -3200. The measurement was performed 3 times in total at any location while changing the measurement location, and the average value was defined as the average thickness.

(3) Variation of powder layer The average value of the absolute value of the difference between the average thickness and the thickness at three measurement points was calculated, and the value was regarded as variation. The variation indicates that the smaller the value, the higher the smoothness of the surface of the powder layer. If the variation is less than 50 μm, the smoothness is very good, and the determination is ◎, and if it is in the range of 50 to 100 μm, the determination is made. Was evaluated as “good”, and when it exceeded 100 μm, the determination was made “poor”.

<2. Angle of repose of electrode active material particle aggregate>
A glass funnel (the length of the funnel foot: 50 mm, the inner diameter: 4 mm) was placed horizontally so that the tip of the funnel was located 10 cm above the surface of the horizontally placed flat metal plate. An electrode active material particle aggregate having an apparent volume of 15 ml was supplied to the funnel using a 15 ml capacity container, and a conical laminate was formed on the metal plate by the electrode active material particle aggregate dropped from the funnel. The angle formed between the portion corresponding to the generatrix of the laminated body and the surface of the metal flat plate was measured using a Keyence 3D shape measuring instrument VR-3200. The angle was measured at a location where the bottom of the cone was divided into 8 equal portions of 45 degrees, and the average value was taken as the repose angle of the electrode active material particle aggregate.

In Table 1, the mixing pan means a rotating container that rotates while containing the contents, and the rotor means a stirring blade arranged in the rotating container. In addition, the FM mixer used in Example 9 and Comparative Example 1 does not rotate the container but rotates the stirring blade in the container.

From the above results, according to the method for producing an electrode active material particle aggregate of the present invention, an electrode active material particle aggregate having high fluidity can be produced, and the electrode active material particle aggregate is suitable for producing an electrode. Yes.

The method for producing electrode active material particle aggregates of the present invention produces electrodes for bipolar secondary batteries and lithium ion secondary batteries used for mobile phones, personal computers, hybrid vehicles and electric vehicles, in particular. Therefore, it is useful as a method for producing an electrode active material particle aggregate used for the purpose.

This application is based on Japanese Patent Application No. 2018-108625 filed on June 6, 2018, the disclosure content of which is incorporated by reference in its entirety.

DESCRIPTION OF SYMBOLS 1 Mixer 3 Stirring blade 4 Rotating container 5 Head part 6 Bar-shaped member 7 Bottom plate B Rotating direction B of ₁ rotating container ₂ Rotating direction CL of ₁ rotating container CL Rotating center axis CL of ₂ rotating blades ₂ Rotating center axis H of ₂ stirring blades Horizontal plane

Claims (8)

1. A method for producing an electrode active material particle aggregate comprising electrode active material particles (a), a conductive additive (b) and an adhesive (c),
   A first mixing step of dry mixing the electrode active material particles (a) and the conductive additive (b) to obtain a mixture;
   In the form of a solution, 0.01 to 10% by mass of the pressure-sensitive adhesive (c) with respect to the total mass of the electrode active material particles (a) is stirred with respect to the mixture obtained in the first mixing step. In addition, a second mixing step to obtain a mixture;
   And a stirring step of stirring the mixture obtained in the second mixing step. A method for producing electrode active material particle aggregates.
2. The method for producing an electrode active material particle aggregate according to claim 1, wherein the concentration of the pressure-sensitive adhesive (c) in the solution is 0.01 to 20% by mass.
3. The method for producing an aggregate of electrode active material particles according to claim 1 or 2, wherein the pressure-sensitive adhesive contains a copolymer containing at least 2-ethylhexyl (meth) acrylate and (meth) acrylic acid as constituent monomers.
4. The total mass of 2-ethylhexyl (meth) acrylate and (meth) acrylic acid in the constituent monomer of the copolymer is 10% by mass or more based on the total mass of the constituent monomers of the copolymer. The manufacturing method of the electrode active material particle aggregate of Claim 3.
5. At least one of the dry mixing in the first mixing step, the stirring in the second mixing step, and the stirring in the stirring step,
   A rotating container that rotates with the contents stored therein, and a stirring blade that is disposed in parallel to the rotation center axis at a position that is inward of the rotation container and eccentric from the rotation center axis of the rotation container,
   The method for producing an electrode active material particle aggregate according to any one of claims 1 to 4, wherein the method is performed using a mixer in which the rotating container and the stirring blade rotate to mix the contents.
6. A head portion that is disposed in parallel with the rotation center axis of the rotating container and is driven to rotate; and at least one rod-like member attached to the head portion and extending to the vicinity of the bottom plate of the rotating container; The method for producing an electrode active material particle aggregate according to claim 5, wherein the rod-shaped member moves circumferentially in the rotary container.
7. An electrode comprising an application step of applying an electrode active material particle aggregate obtained by the method for producing an electrode active material particle aggregate according to any one of claims 1 to 6 on a substrate. Manufacturing method.
8. The method for producing an electrode according to claim 7, further comprising a pressurizing step of pressurizing the electrode active material particle aggregate applied on the substrate.

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