JP2019164887A - Production method of paste for negative electrode production, negative electrode for battery, battery and production method of negative electrode for battery - Google Patents

Abstract

To provide a production method of a paste for negative electrode production, by which a negative electrode of a battery superior in the adhesion of a current collector layer and a negative electrode active material layer can be obtained with stability.SOLUTION: A production method of a paste for negative electrode production according to the present invention comprises the steps of: (A) preparing a mixture (M1) containing at least a negative electrode active material and a first thickener by mixing the negative electrode active material and the first thickener; (B) preparing a paste precursor by adding one or more liquid components selected from emulsion aqueous solutions each containing an aqueous medium and an aqueous binder to the mixture (M1) and mixing them in a wet manner; and (C) preparing the paste for negative electrode production by further adding the one or more liquid components to the paste precursor and mixing them in a wet manner. The step (B) comprises the step (B1) of obtaining a mixture (M2) by making the one or more liquid components fit in with the mixture (M1), the step (B2) of obtaining a mixture (M3) by mixing a second thickener and the one or more liquid components in the mixture (M2) and the step (B3) of obtaining the paste precursor by stiffening the mixture (M3) at least in this order.SELECTED DRAWING: None

Description

  The present invention relates to a method for manufacturing a negative electrode manufacturing paste, a battery negative electrode, a battery, and a battery negative electrode manufacturing method.

  In general, a negative electrode used in a battery is mainly composed of a negative electrode active material layer and a current collector layer. The negative electrode active material layer can be obtained, for example, by applying and drying a negative electrode manufacturing paste containing a negative electrode active material, a thickener, an aqueous binder, and the like on the surface of a current collector layer such as a metal foil.

  As a manufacturing method of the negative electrode for batteries, for example, the method described in Patent Document 1 can be mentioned.

  In Patent Document 1 (Japanese Patent No. 5339689), carbon powder 1a and CMC powder 1b are charged and mixed in a powder-only state to produce a powder mixture 1, and then the viscosity, particle size, and peel strength of the paste Of the lithium-ion secondary battery, in which the amount of the dispersion medium input and the kneading time are determined based on the correlation with each other and the water as the dispersion medium is charged in two steps, a rough kneading process and a kneading process. A method for producing a paste used for production is described.

Japanese Patent No. 5339689

According to the study by the present inventors, the negative electrode for a battery obtained by a conventional manufacturing method may have low peel strength, and there is room for improvement in the adhesion between the current collector layer and the negative electrode active material layer. Became clear.
When the peel strength of the negative electrode for the battery is low, the productivity of the electrode or the battery is reduced, or the negative electrode active material layer is powdered off in the process of assembling the battery. As a result, the quality of the battery, the cycle characteristics of the battery, etc. There is a concern that problems may occur.

  The present invention has been made in view of the above circumstances, and a method for producing a paste for producing a negative electrode capable of stably obtaining a negative electrode for a battery having excellent adhesion between a current collector layer and a negative electrode active material layer Is to provide.

  The present inventors have intensively studied to achieve the above-mentioned problems. As a result, a negative electrode for a battery having excellent adhesion between the current collector layer and the negative electrode active material layer can be stably obtained by using a method for manufacturing a negative electrode manufacturing paste in which a thickener is mixed in two stages. The present invention has been completed by finding out that it can be obtained.

That is, according to the present invention,
(A) preparing a mixture (M1) containing at least the negative electrode active material and the first thickener by mixing the negative electrode active material and the first thickener;
(B) a step of preparing a paste precursor by adding one or two or more liquid components selected from an aqueous emulsion containing an aqueous medium and an aqueous binder to the mixture (M1) and wet-mixing the mixture (M1); ,
In the paste precursor, the liquid component is further added and wet mixed to prepare a negative electrode manufacturing paste (C);
A method for producing a paste for producing a negative electrode, comprising:
The step (B)
A step (B1) of obtaining the mixture (M2) by allowing the liquid component to be mixed with the mixture (M1);
A step (B2) of obtaining a mixture (M3) by mixing the second thickener and the liquid component in the mixture (M2);
There is provided a method for producing a paste for producing a negative electrode, comprising at least a step (B3) of obtaining the paste precursor by kneading the mixture (M3).

Moreover, according to the present invention,
A current collector layer;
There is provided a negative electrode for a battery comprising a negative electrode active material layer provided on at least one surface of the current collector layer and formed by a solid content of the negative electrode production paste of the present invention.

Moreover, according to the present invention,
A battery comprising at least a positive electrode, an electrolyte, and a negative electrode,
A battery is provided in which the negative electrode includes the negative electrode for a battery of the present invention.

According to the present invention,
The negative electrode production paste obtained by the method for producing a negative electrode production paste of the present invention is applied to a current collector layer, dried, and the aqueous medium is removed to thereby form the negative electrode active material on the current collector layer. A method for producing a negative electrode for a battery including a step of forming a material layer is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the paste for negative electrode manufacture which can obtain stably the negative electrode for batteries excellent in the adhesiveness of a collector layer and a negative electrode active material layer can be provided.

It is sectional drawing which shows an example of the structure of the negative electrode for batteries of embodiment which concerns on this invention. It is sectional drawing which shows an example of the structure of the battery of embodiment which concerns on this invention.

Embodiments of the present invention will be described below with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate. Also, in the figure, each component schematically shows the shape, size, and arrangement relationship to the extent that the present invention can be understood, and is different from the actual size.
In the present embodiment, unless otherwise specified, a layer including a negative electrode active material is referred to as a negative electrode active material layer, and a layer obtained by forming a negative electrode active material layer on a current collector layer is referred to as an electrode. In the present embodiment, the numerical range “A to B” represents A or more and B or less unless otherwise specified.

<Method for producing paste for producing negative electrode>
The manufacturing method of the negative electrode manufacturing paste according to the present embodiment is a step of preparing a mixture (M1) containing at least the negative electrode active material and the first thickener by mixing the negative electrode active material and the first thickener ( A) and a step of preparing a paste precursor by adding one or two or more liquid components selected from an aqueous emulsion solution containing an aqueous medium and an aqueous binder to the mixture (M1) and wet-mixing them ( B) and a step (C) of preparing a paste for producing a negative electrode by further adding a liquid component to the paste precursor and performing wet mixing.
And in the manufacturing method of the paste for negative electrode manufacture which concerns on this embodiment, the said process (B) is a process (B1) which obtains a mixture (M2) by making the said liquid component blend into the said mixture (M1), and the said A step (B2) of obtaining a mixture (M3) by mixing the second thickener and the liquid component in the mixture (M2), and a step of obtaining the paste precursor by kneading the mixture (M3) ( B3) at least in this order.
Here, in the negative electrode production paste according to the present embodiment, the first thickener and the second thickener are dissolved in the negative electrode production paste and are not in a powder state.
The battery according to the present embodiment is, for example, a lithium ion primary battery or a lithium ion secondary battery, and preferably a lithium ion secondary battery.

As described above, according to the study by the present inventors, the negative electrode for a battery obtained by a conventional manufacturing method may have a low peel strength, which improves the adhesion between the current collector layer and the negative electrode active material layer. It became clear that there was room for.
When the peel strength of the negative electrode for the battery is low, the productivity of the electrode or the battery is reduced, or the negative electrode active material layer is powdered off in the process of assembling the battery. There is a concern that problems may occur.

The present inventors have intensively studied to achieve the above-mentioned problems. As a result, in the stage before the step (B3) of kneading the slurry, by mixing the thickener in two stages, the first thickener and the second thickener, The present invention was completed by finding that a negative electrode for a battery excellent in adhesiveness with the negative electrode active material layer can be stably obtained.
Here, by mixing the thickener in two stages of the first thickener in the step (A) and the second thickener in the step (B2), the current collector layer and the negative electrode active material layer are mixed. The reason why a negative electrode for a battery having excellent adhesiveness can be stably obtained is not necessarily clear, but the following reasons are conceivable.
First, in the step (A), it is considered that the first thickener is adsorbed on the surface of the negative electrode active material by mixing the negative electrode active material and the first thickener.
Further, after obtaining the mixture (M2) by blending the liquid component into the mixture (M1), by mixing the second thickener, the first thickener remains adsorbed on the surface of the negative electrode active material, It is believed that the second thickener can be dispersed in the liquid component.
In the thus obtained negative electrode manufacturing paste precursor, most of the negative electrode active material exists as an aggregate in which the first thickener excellent in adsorptivity with the aqueous binder is adsorbed on the surface, and the second thickener is present. It is considered that the liquid component is present in a free state without being adsorbed on the surface of the negative electrode active material. As a result, the aqueous binder is efficiently adsorbed on the aggregate, a three-dimensional network is developed by the interaction between the materials, and the second thickener not adsorbed on the negative electrode active material is contained in the liquid. Disperse in a moderately free state.
For this reason, in the step of subsequently applying the negative electrode manufacturing paste to the current collector layer and drying, further removing the aqueous medium and forming the negative electrode active material layer on the current collector layer, It is thought that the 2nd thickener disperse | distributed in free state in said paste suppresses the movement to the negative electrode active material layer surface of the aqueous binder at the time of drying. Furthermore, since the three-dimensional network by the interaction between each material has developed, it is thought that the movement to the surface of the negative electrode active material layer of the aqueous binder at the time of drying is further suppressed. As a result of these synergistic effects, it is considered that the aqueous binder can be prevented from being unevenly distributed on the surface of the negative electrode active material layer.
As a result of suppressing the surface uneven distribution of the aqueous binder in the negative electrode active material layer, the amount of the aqueous binder at the interface between the current collector layer and the negative electrode active material layer can be increased, and the current collector layer and the negative electrode active material It is considered that the adhesion with the layer, that is, the peel strength can be improved.

That is, according to the manufacturing method of the negative electrode manufacturing paste according to the present embodiment, the thickener is mixed in two stages of the first thickener in the step (A) and the second thickener in the step (B2). By doing so, uneven distribution of the water-based binder on the surface of the negative electrode active material layer can be suppressed, and adhesion between the current collector layer and the negative electrode active material layer, that is, peel strength can be improved.
As described above, according to this embodiment, it is possible to provide a negative electrode manufacturing paste capable of stably obtaining a negative electrode for a battery excellent in adhesiveness between a current collector layer and a negative electrode active material layer.

From the viewpoint of improving the dispersion stability of the negative electrode manufacturing paste, the pH of the negative electrode manufacturing paste according to the present embodiment is, for example, 6.0 or more and 8.0 or less, preferably 6.5 or more and 7.5 or less. More preferably, it is 6.8 or more and 7.2 or less.
The method for adjusting the pH of the negative electrode production paste according to the present embodiment is not particularly limited. For example, the mixing ratio of each material constituting the negative electrode production paste, the type of each material constituting the negative electrode production paste, and the like. It can be adjusted by adjusting.

<Constituent material of paste for producing negative electrode>
Next, each material which comprises the paste for negative electrode manufacture which concerns on this embodiment is demonstrated. The negative electrode manufacturing paste according to this embodiment includes a negative electrode active material, an aqueous binder, a thickener (the first thickener and the second thickener are collectively referred to as a thickener), and an aqueous medium. And, if necessary, a conductive aid.

(Negative electrode active material)
In the present embodiment, when the negative electrode active material is used as the electrode active material and the negative electrode manufacturing paste is a paste for forming a negative electrode for a battery, the effect of improving the peel strength of the present embodiment is particularly effective. Obtainable.

The negative electrode active material is not particularly limited as long as it is a normal negative electrode active material that can be used for a negative electrode of a battery. When the battery is a lithium ion battery, for example, carbon materials such as natural graphite, artificial graphite, resin charcoal, carbon fiber, activated carbon, hard carbon, and soft carbon; lithium metals such as lithium metal and lithium alloy; silicon and tin And conductive polymers such as polyacene, polyacetylene, and polypyrrole. Among these, carbon materials are preferable, and graphite materials such as natural graphite and artificial graphite are particularly preferable.
A negative electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the negative electrode active material is preferably 70 parts by mass or more and 99.97 parts by mass or less, and 85 parts by mass or more and 99.85 parts by mass, when the total solid content of the negative electrode production paste is 100 parts by mass. The following is more preferable.

The graphite material is not particularly limited as long as it is a normal graphite material that can be used for the negative electrode of the battery. When the said battery is a lithium ion battery, the artificial graphite etc. which are manufactured by heat-processing natural graphite, petroleum-type, and coal-type coke are mentioned, for example.
Here, natural graphite refers to graphite that is naturally produced as ore. There are no particular restrictions on the origin, properties, and types of natural graphite used as the core material of this embodiment.
Artificial graphite refers to graphite produced by an artificial technique and graphite close to perfect crystals of graphite. Such artificial graphite can be obtained, for example, by using a tar or coke obtained from coal residue, crude oil distillation residue, or the like as a raw material, followed by a firing step and a graphitization step.

Further, the graphite material has graphite powder as a core material, and at least a part of the surface of the graphite powder is coated with a carbon material having lower crystallinity than the graphite powder (hereinafter also referred to as surface-coated graphite). ) Is preferred. In particular, the edge portion of the graphite powder is preferably covered with the carbon material. By covering the edge portion of the graphite powder, the irreversible reaction between the edge portion and the electrolyte can be suppressed, and as a result, the initial charge / discharge efficiency can be prevented from lowering due to the increase in the irreversible capacity. it can.
In addition, when surface-coated graphite is used, the binding property with the binder can be improved as compared with the case of graphite alone, so that the amount of the binder can be reduced. As a result, the battery characteristics of the obtained battery can be improved.
Here, the carbon material having lower crystallinity than the graphite powder is, for example, amorphous carbon such as soft carbon and hard carbon.

  Examples of the graphite powder used as the core material include artificial graphite produced by heat-treating natural graphite, petroleum-based and coal-based coke. In this embodiment, these graphite powders may be used alone or in combination of two or more. Among these, natural graphite is preferable from the viewpoint of cost.

  The surface-coated graphite according to the present embodiment is obtained by carbonizing the organic compound after the carbon powder is carbonized by the firing process and becomes a carbon material having lower crystallinity than the graphite powder and the graphite powder. It can produce by doing.

The organic compound mixed with the graphite powder is not particularly limited as long as it is carbonized by firing to obtain a carbon material having lower crystallinity than the graphite powder. For example, petroleum-based tar, coal-based tar Tars such as petroleum pitch, coal pitch, etc .; thermoplastic resins such as polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl alcohol, polyvinylidene chloride, polyacrylonitrile; heat of phenol resin, furfuryl alcohol resin, etc. Examples thereof include curable resins; natural resins such as cellulose; aromatic hydrocarbons such as naphthalene, alkylnaphthalene, and anthracene.
In this embodiment, these organic compounds may be used individually by 1 type, and may be used in combination of 2 or more type. Further, these organic compounds may be used by dissolving or dispersing in a solvent as necessary.
Among the above organic compounds, tar and pitch are preferable from the viewpoint of price.

The ratio of the carbon material derived from the organic compound in the surface-coated graphite according to the present embodiment (hereinafter referred to as “coating amount”) is preferably 0.7% by mass or more and 8.% by mass when the negative electrode active material is 100% by mass. 0% by mass or less.
By setting the coating amount of the carbon material to the upper limit value or less, the area for storing and releasing lithium ions is increased, and the rate characteristics of the obtained lithium ion battery can be improved.
By making the coating amount of the carbon material equal to or more than the above lower limit value, it is possible to suppress a decrease in initial charge / discharge efficiency due to an increase in irreversible capacity. Moreover, stability of the paste for negative electrode manufacture obtained can be improved by making the coating amount of a carbon material more than the said lower limit.
Here, the coating amount can be calculated by thermogravimetric analysis. More specifically, when the temperature of the negative electrode active material is increased to 900 ° C. at a temperature increase rate of 5 ° C./min in an oxygen atmosphere using a thermogravimetric analyzer (for example, TGA7 analyzer manufactured by Perkin Elma), the mass The reduced mass from the temperature at which the decrease starts to the temperature at which the mass decrease rate becomes moderate and then the mass decrease accelerates can be used as the coating amount.

The specific surface area of the negative electrode active material by nitrogen adsorption BET method is preferably 1.0 m ² / g or more and 6.0 m ² / g or less, more preferably 2.0 m ² / g or more and 5.0 m ² / g or less. is there.
By making a specific surface area below the said upper limit, the fall of the initial charging / discharging efficiency by the increase in an irreversible capacity | capacitance can be suppressed. Moreover, stability of the paste for negative electrode manufacture obtained can be improved by making a specific surface area below into the said upper limit.
By setting the specific surface area to be equal to or greater than the above lower limit, the area for inserting and extracting lithium ions is increased, and the rate characteristics of the obtained lithium ion battery can be improved.
Moreover, the binding property of an aqueous binder can be improved by making a specific surface area into the said range.

The average particle size of the negative electrode active material is preferably 1 μm or more, more preferably 3 μm or more, further preferably 5 μm or more, and particularly preferably 8 μm or more, from the viewpoint of suppressing side reactions during charge / discharge and suppressing the decrease in charge / discharge efficiency. From the viewpoint of input / output characteristics and electrode production (such as electrode surface smoothness), it is preferably 50 μm or less, more preferably 40 μm or less, and particularly preferably 30 μm or less. Here, the average particle diameter means a particle diameter (median diameter: d ₅₀ ) at an integrated value of 50% in a particle size distribution (volume basis) by a laser diffraction scattering method.

(Water-based binder)
The water-based binder is not particularly limited as long as it can be electrode-molded and has sufficient electrochemical stability. For example, a rubber-based binder resin or an acrylic-based binder resin can be used. In the present embodiment, the aqueous binder resin refers to a resin that can be dispersed in water to form an aqueous emulsion solution.
The aqueous binder according to the present embodiment is preferably formed of latex particles and dispersed in water to be used as an aqueous emulsion solution. That is, the aqueous binder according to the present embodiment is preferably formed of latex particles of an aqueous binder. Thereby, a water-based binder resin can be contained in a negative electrode active material layer, without inhibiting the contact between negative electrode active materials, between conductive support agents, and between a negative electrode active material and a conductive support agent.

Examples of the rubber binder resin include styrene / butadiene copolymer rubber.
As the acrylic binder resin, for example, a polymer (homopolymer or acrylic acid, methacrylic acid, acrylic ester, methacrylic ester, acrylate, or methacrylate unit (hereinafter referred to as “acryl unit”)). Copolymer) and the like. Examples of the copolymer include a copolymer containing an acrylic unit and a styrene unit, and a copolymer containing an acrylic unit and a silicon unit.
These aqueous binder resins may be used alone or in combination of two or more. Among these, styrene / butadiene copolymer rubber is particularly preferable from the viewpoints of excellent binding properties, affinity with an electrolytic solution, price, electrochemical stability, and the like.

  The content of the aqueous binder is preferably 0.01 parts by mass or more and 10.0 parts by mass or less, and 0.05 parts by mass or more and 5. parts by mass or less, when the total solid content of the negative electrode production paste is 100 parts by mass. More preferably, it is 0 parts by mass or less. When the content of the aqueous binder is within the above range, the balance of the coating property of the paste for producing a negative electrode, the binding property of the binder, and the battery characteristics is further improved.

As the aqueous binder, for example, a powdery material is dispersed in an aqueous medium and used as an aqueous emulsion solution. Thereby, the dispersibility of a water-based binder can be improved, without inhibiting the contact between negative electrode active materials, between conductive support agents, and between a negative electrode active material and a conductive support agent.
The aqueous medium in which the aqueous binder is dispersed is not particularly limited as long as the aqueous binder can be dispersed, but distilled water, ion exchange water, city water, industrial water, and the like can be used. Among these, distilled water and ion exchange water are preferable. The water may be mixed with water such as alcohol and a highly hydrophilic solvent.

Styrene-butadiene copolymer rubber is a copolymer containing styrene and 1,3-butadiene as main components. Here, the main component is a total content of styrene-butadiene copolymer rubber in which the total content of styrene-derived structural units and 1,3-butadiene-derived structural units in the styrene-butadiene copolymer rubber is This refers to the case of 50% by mass or more.
The mass ratio (St / BD) between the structural unit derived from styrene (hereinafter also referred to as St) and the structural unit derived from 1,3-butadiene (hereinafter also referred to as BD) is, for example, 10/90 to 90 / 10.

The styrene / butadiene copolymer rubber may be copolymerized with monomer components other than styrene and 1,3-butadiene. Examples thereof include conjugated diene monomers, unsaturated carboxylic acid monomers, and other known monomers that can be copolymerized.
Examples of the conjugated diene monomer include isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, piperylene and the like.
Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid and the like.

The method for producing the styrene / butadiene copolymer rubber is not particularly limited, but it is preferably produced by an emulsion polymerization method. When the emulsion polymerization method is used, latex particles containing styrene / butadiene copolymer rubber can be obtained.
Conventionally known methods can be used for emulsion polymerization. For example, styrene, 1,3-butadiene, and the above-mentioned various copolymerizable monomer components are preferably produced by emulsion polymerization in water with the addition of a polymerization initiator, preferably in the presence of an emulsifier. Can do.

(Thickener)
A thickener will not be specifically limited if it improves the applicability | paintability of the paste for negative electrode manufacture. Examples of the thickener include water-soluble polymers such as a cellulose-based water-soluble polymer; polycarboxylic acid; polyethylene oxide; polyvinyl pyrrolidone; polyacrylic acid salt such as sodium polyacrylate; These thickeners may be used individually by 1 type, and may be used in combination of 2 or more type.
Among these, cellulose-based water-soluble polymers are preferable.

The cellulose-based water-soluble polymer is not particularly limited as long as it improves the coatability of the negative electrode manufacturing paste. Examples of the cellulose-based water-soluble polymer include cellulose polymers such as carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, methylethylhydroxycellulose, methylcellulose, hydroxypropylcellulose, and ammonium salts and alkali metal salts of these cellulose polymers. 1 type, or 2 or more types selected from the cellulose-type polymer salt etc. of this can be used.
Among these, it is preferable to include at least one selected from carboxymethyl cellulose and carboxymethyl cellulose salt, one or more selected from carboxymethyl cellulose, ammonium salt of carboxymethyl cellulose, sodium salt of carboxymethyl cellulose and potassium salt of carboxymethyl cellulose It is more preferable to contain.

The solubility of the cellulose-based water-soluble polymer in an aqueous medium can be improved, the solid content concentration of the negative electrode manufacturing paste can be increased, the elastic modulus of the obtained negative electrode manufacturing paste can be improved, etc. Therefore, the degree of etherification of the cellulose-based water-soluble polymer is preferably 0.50 or more and 1.0 or less, and more preferably 0.70 or more and 0.90 or less.
Here, the degree of etherification refers to the degree of substitution of a hydroxyl group with a carboxymethyl group or the like per anhydroglucose unit in a cellulose-based water-soluble polymer.

The weight average molecular weight Mw (polyethylene glycol equivalent value) of the cellulose-based water-soluble polymer measured by gel permeation chromatography (GPC) is preferably 100,000 or more, and more preferably 200,000 or more. When the weight average molecular weight Mw of the cellulose-based water-soluble polymer is not less than the above lower limit, the storage elastic modulus of the paste for producing a negative electrode according to this embodiment can be effectively increased.
Moreover, the weight average molecular weight Mw (polyethylene glycol equivalent value) of the cellulose-based water-soluble polymer measured by GPC is preferably 900000 or less, and more preferably 800000 or less. When the weight-average molecular weight Mw of the cellulose-based water-soluble polymer is not more than the above upper limit, the solubility of the cellulose-based water-soluble polymer in the aqueous medium can be improved, and the solid content concentration of the negative electrode manufacturing paste can be increased. As a result, the storage elastic modulus of the negative electrode manufacturing paste according to the present embodiment can be effectively increased.

  The content of the thickener (total content of the first thickener and the second thickener) is 0.01 parts by mass or more and 10.10 parts by mass when the total solid content of the paste for negative electrode production is 100 parts by mass. It is preferably 0 parts by mass or less, and more preferably 0.05 parts by mass or more and 5.0 parts by mass or less. When the content of the thickener is within the above range, the balance of the coating property of the paste for producing a negative electrode, the binding property of the binder, and the battery characteristics is further improved.

(Conductive aid)
From the viewpoint of improving the electronic conductivity of the obtained electrode, the negative electrode producing paste according to this embodiment preferably further contains a conductive additive.
The conductive auxiliary agent is not particularly limited as long as it has electronic conductivity and improves the conductivity of the electrode. Examples of the conductive additive according to the present embodiment include acetylene black, ketjen black, carbon black, carbon nanofibers, and carbon materials such as graphite having a smaller particle diameter than graphite used as an active material. These conductive aids may be used alone or in combination of two or more.

The content of the conductive assistant is preferably 0.01 parts by mass or more and 10.0 parts by mass or less, and 0.05 parts by mass or more and 5 parts by mass or less, when the total solid content of the paste for negative electrode production is 100 parts by mass. More preferably, it is 0.0 parts by mass or less.
When the content of the conductive auxiliary agent is within the above range, the balance between the coating property of the negative electrode producing paste and the binding property of the binder is further improved.

The specific surface area of the conductive aid by the nitrogen adsorption BET method is preferably 50 m ² / g or more and 1000 m ² / g or less from the viewpoint of the balance between the coating property of the negative electrode production paste and the conductivity of the electrode.

(Aqueous medium)
It does not specifically limit about the aqueous medium which concerns on this embodiment, For example, distilled water, ion-exchange water, city water, industrial water etc. can be used. Among these, distilled water and ion exchange water are preferable. The water may be mixed with water such as alcohol and a highly hydrophilic solvent.

In the negative electrode production paste according to this embodiment, when the total solid content of the negative electrode production paste is 100 parts by mass, the content of the negative electrode active material is preferably 70 parts by mass or more and 99.97 parts by mass or less, More preferably, it is 85 to 99.85 parts by mass. Further, the content of the aqueous binder is preferably 0.01 parts by mass or more and 10.0 parts by mass or less, more preferably 0.05 parts by mass or more and 5.0 parts by mass or less. Further, the content of the thickener (the total content of the first thickener and the second thickener) is preferably 0.01 parts by mass or more and 10.0 parts by mass or less, more preferably 0.05 parts by mass. Part to 5.0 parts by weight. Further, the content of the conductive assistant is preferably 0.01 parts by mass or more and 10.0 parts by mass or less, and more preferably 0.05 parts by mass or more and 5.0 parts by mass or less.
When the content of each component constituting the negative electrode production paste is within the above range, the balance between the quality stability of the negative electrode production paste and the battery characteristics of the obtained battery is particularly excellent.

<Method for producing paste for producing negative electrode>
Next, the manufacturing method of the paste for water electrode manufacture which concerns on this embodiment is demonstrated.
The manufacturing method of the negative electrode manufacturing paste according to the present embodiment includes a negative electrode active material, an aqueous binder, a thickener, and an aqueous medium, and further includes a conductive additive as necessary. It is a manufacturing method of a paste, Comprising: At least the following processes (A)-(C) are included.

Step (A): Step of preparing a mixture (M1) containing at least the negative electrode active material and the first thickener by mixing the negative electrode active material and the first thickener Step (B): The mixture (M1) ) In which a paste precursor is prepared by adding one or two or more liquid components selected from an aqueous emulsion containing an aqueous medium and an aqueous binder and wet mixing Step (C): the paste precursor A step of preparing a paste for producing a negative electrode by further adding the liquid component to the body and performing wet mixing

In step (A), the negative electrode active material and the first thickener are mixed to prepare a mixture (M1) containing at least the negative electrode active material and the first thickener. At this time, you may mix and mix a conductive support agent.
In the step (A), it is preferable to dry-mix a plurality of powdered materials including at least the negative electrode active material and the first thickener in a powder state. By dry-mixing the negative electrode active material and the first thickener in a powder state, a powder mixture containing the negative electrode active material and the first thickener can be prepared. At this time, you may mix a powder with a conductive support agent. In this embodiment, a 1st thickener can be made to adsorb | suck to the surface of a negative electrode active material by performing a process (A).
Here, although the step (A) may be performed by wet mixing, the solid content concentration in the step (A) is preferably 95% by mass or more and 100% by mass or less, for example. By making it into the said range of solid content concentration in a process (A), a 1st thickener can be more effectively adsorbed on the surface of a negative electrode active material.

  As the mixer for performing the step (A), a planetary motion type mixer is preferably used, and a planetary motion type planetary mixer is more preferably used. By using such a mixer, the negative electrode active material and the first thickener can be sufficiently mixed while suppressing scattering of the negative electrode active material and the first thickener. Note that the planetary motion mixer refers to a mixer having a rotation and revolution function as a stirring mechanism. The planetary motion type planetary mixer is a mixer having blades having rotation and revolution functions as a stirring mechanism.

Shear rate of mixing in step (A) is preferably in the range of 1.0 sec ^-1 or more 26.0Sec ^-1 or less, in the range of 6.5Sec ^-1 or more 19.5Sec ^-1 or less Is more preferable.
When the shear rate of mixing in the step (A) is within the above range, the negative electrode active material and the first thickener can be sufficiently mixed while suppressing the scattering of the negative electrode active material and the first thickener. it can.

  Although the mixing time in a process (A) is not specifically limited, For example, 5 minutes or more and 120 minutes or less, Preferably they are 10 minutes or more and 60 minutes or less.

  In the step (B), one or two or more liquid components selected from an aqueous emulsion containing an aqueous medium and an aqueous binder are added to the mixture (M1) obtained in the step (A) and wet-mixed. To prepare a paste precursor.

  As the mixer for performing the wet mixing in the step (B), it is preferable to use a planetary motion type mixer, and it is more preferable to use a planetary motion type planetary mixer. By using such a mixer, the dispersibility of each material can be enhanced while suppressing the scattering of each material constituting the paste for producing a negative electrode.

  Here, the step (B) is a step (B1) of obtaining the mixture (M2) by blending the liquid component into the mixture (M1), and the second thickener and the liquid component are mixed into the mixture (M2). The step (B2) for obtaining the mixture (M3) by doing this and the step (B3) for obtaining the paste precursor by kneading the mixture (M3) are at least three steps in this order. .

  The step (B1) of obtaining the mixture (M2) by blending the liquid component into the mixture (M1) is one or more liquids selected from emulsion aqueous solutions containing an aqueous medium and an aqueous binder in the mixture (M1). This is the process of blending the ingredients. The mixture (M2) obtained in the step (B1) is in a state where the liquid component is familiar to the powder of the negative electrode active material, for example, but is not in a clay state and is in a fluid state. That is, in the step (B1), it is preferable to knead the mixture (M1) in a fluid state to obtain a mixture (M2) in a fluid state. By including this blending step (B1), it is possible to prevent the mixture from rising on the edge of the mixer during wet mixing, uneven wetting of the mixture, and scattering of the mixture during kneading within a certain range. Can be suppressed.

Shear rate of wet mixing in the step (B1), it is preferably, 26.0Sec ^-1 or more 40.0Sec ^-1 within the range in the range of 6.5Sec ^-1 or more 55.5Sec ^-1 or less It is more preferable.
If the shear rate of the wet mixing in the step (B1) is within the above range, the mixture may rise on the edge of the mixer during wet mixing, the mixture may be unevenly wet, or the mixture may scatter during kneading. The liquid component can be fully adapted to the mixture while suppressing the above and the like more effectively.

  Although the mixing time of the wet mixing in the step (B1) is not particularly limited, for example, it is preferably 0.5 minutes or more and 60 minutes or less, and more preferably 10 minutes or more and 30 minutes or less.

In the step (B1), the solid content concentration of the mixture (M2) is preferably adjusted to 71% by mass to 95% by mass, more preferably 73% by mass to 94% by mass, and more preferably 74% by mass or more. It is more preferable to adjust to 91 mass% or less, and it is especially preferable to adjust to 77 mass% or more and 86 mass% or less.
In the step (B1), by setting the solid content concentration of the mixture (M2) to the lower limit value or more, the first thickener is easily adsorbed on the surface of the negative electrode active material. Excess dispersion of the sticking agent is further suppressed. It is considered that most of the negative electrode active material is dispersed in the aqueous medium in the subsequent step (B2) and step (B3), in the state of the aggregate with the first thickener adsorbed on the surface. Since the first thickener is more adsorbable with the aqueous binder than the negative electrode active material itself, the aqueous binder is efficiently adsorbed on the aggregate, and a three-dimensional network based on the interaction between the materials is formed. It is considered to develop. As a result, the adhesion between the current collector layer and the negative electrode active material layer, that is, the peel strength, can be further improved in the negative electrode obtained by subsequently applying and drying the negative electrode production paste on the current collector. it can.
In the method for manufacturing a negative electrode manufacturing paste according to the present embodiment, the solid content concentration of the mixture (M2) in the step (B1) is set to be equal to or lower than the above upper limit value, so that the mixture containing the negative electrode active material is Therefore, it is possible to effectively suppress the rising, and thus it is possible to obtain a negative electrode manufacturing paste having a stable viscosity and mixing ratio.

Moreover, a process (B2) is a process of obtaining a mixture (M3) by mixing a 2nd thickener and the said liquid component with a mixture (M2).
In the step (B2), it is preferable to mix the second thickener in a powder state with the mixture (M2). By doing so, it is possible to knead the mixture (M2) while suppressing a decrease in the solid content concentration of the mixture (M2), and knead the mixture (M2) while applying higher shear. it can.

  It is preferable that the 1st thickener mixed at the process (A) and the 2nd thickener mixed at the process (B2) are the same types. By doing so, the design of the negative electrode manufacturing paste and the management of the thickener are further facilitated.

In the method for producing a paste for producing a water electrode according to this embodiment, it is preferable that the amount of the second thickener mixed is larger than the amount of the first thickener mixed.
More specifically, the mixing amount of the first thickener is preferably 45% by mass or less when the total mixing amount of the first thickener and the second thickener is 100% by mass, It is more preferably at most mass%, further preferably at most 35 mass%, particularly preferably at most 30 mass%. By doing this, the amount of the second thickener dispersed in the negative electrode manufacturing paste in a free state can be increased, so that the movement of the aqueous binder to the negative electrode active material layer surface during drying is further suppressed. Can do. As a result, since the aqueous binder can be further suppressed from being unevenly distributed on the surface of the negative electrode active material layer, the amount of the aqueous binder at the interface between the current collector layer and the negative electrode active material layer can be increased. The adhesion between the body layer and the negative electrode active material layer, that is, the peel strength can be further improved.
The mixing amount of the first thickener is preferably 1% by mass or more, preferably 5% by mass or more when the total mixing amount of the first thickener and the second thickener is 100% by mass. More preferably, it is more preferably 10% by mass or more. By doing so, the amount of the first thickener adsorbed on the surface of the negative electrode active material can be increased, and as a result, a three-dimensional network due to the interaction between the materials further develops, The movement of the aqueous binder to the negative electrode active material layer surface can be further suppressed. As a result, since the aqueous binder can be further suppressed from being unevenly distributed on the surface of the negative electrode active material layer, the amount of the aqueous binder at the interface between the current collector layer and the negative electrode active material layer can be increased. The adhesion between the body layer and the negative electrode active material layer, that is, the peel strength can be further improved.
Further, in the step (A), when the first thickener is not mixed at all, the paste precursor aggregates in the step (B), and a desired paste for producing a negative electrode can be prepared. There wasn't. The reason why such agglomeration of the paste precursor occurs is not necessarily clear, but if the first thickener is not mixed at all, the negative electrode active material and the thickener are not uniformly mixed, and many of the negative electrode active materials are formed on the surface. The second thickener added in the step (B2) does not exist as an aggregate in which the first thickener excellent in adsorptivity with the water-based binder is adsorbed, and is around some negative electrode active materials. It becomes a state that is unevenly distributed only. If it does so, it will be thought that adsorption | suction of an aqueous binder advances preferentially to the negative electrode active material in which said thickener was unevenly distributed in the step which added the aqueous binder.

Step (B3) is a step of obtaining a paste precursor by kneading the mixture (M3) obtained in step (2). The paste precursor obtained in the step (B3) is in a clay state, for example. That is, in the step (B3), the mixture (M3) becomes a clay state as the kneading proceeds, and as a result, it is preferable to obtain a paste precursor in a clay state.
Here, it is preferable to set the solid content concentration of the paste precursor in the step (B3) to be lower than the solid content concentration of the mixture (M2) in the step (B1). Thereby, the mixture (M3) becomes a clay state as the kneading progresses, and as a result, higher shear can be applied, and the mixture (M3) can be sufficiently kneaded.

In the step (B3), the solid content concentration of the mixture (M3) is preferably adjusted to 55% by mass or more and less than 75% by mass, more preferably adjusted to 56% by mass or more and 72% by mass or less, and 57% by mass or more. It is more preferable to adjust to 70 mass% or less, and it is especially preferable to adjust to 59 mass% or more and 66 mass% or less.
In the step (B3), by setting the solid content concentration of the mixture (M3) to the lower limit value or more, the adsorption state of the first thickener adsorbed on the negative electrode active material can be maintained. Excessive dispersion of the first thickener in is suppressed. The aqueous binder added in the subsequent paste preparation step (C) for negative electrode production is efficiently adsorbed by the active material adsorbed by the first thickener, and a three-dimensional network based on the interaction between the materials is formed. Develop. As a result, the adhesion between the current collector layer and the negative electrode active material layer, that is, the peel strength, can be further improved in the negative electrode obtained by subsequently applying and drying the negative electrode production paste on the current collector. it can.
By setting the solid content concentration of the mixture (M3) to be equal to or higher than the lower limit, it is possible to suppress the solid mixture from being in a so-called lumpy state and to produce a uniform paste.
By setting the solid content concentration of the mixture (M3) to the upper limit value or less, the second thickener can be more uniformly dispersed in the aqueous medium. Thus, in the step of subsequently applying the negative electrode manufacturing paste to the current collector layer and drying, further removing the aqueous medium, and forming the negative electrode active material layer on the current collector layer, The second thickener dispersed in the paste further suppresses the movement of the aqueous binder to the negative electrode active material layer surface during drying, and as a result, the aqueous binder is unevenly distributed on the surface of the negative electrode active material layer. This can be further suppressed.
In addition, by setting the solid content concentration of the mixture (M3) to be equal to or lower than the above upper limit value, it is possible to effectively suppress the mixture (M3) from rising on the edge of the mixer during wet mixing. A paste for negative electrode production with a mixing ratio can be obtained.

  The step (B3) is preferably performed in one step from the viewpoint of simplifying the manufacturing process or shortening the manufacturing time. That is, in the step (B3), the solid content concentration of the mixture (M3) and the solid content concentration of the paste precursor are preferably the same.

  Although the mixing time of the said wet mixing in a process (B3) is not specifically limited, For example, they are 5 minutes or more and 120 minutes or less.

Shear rate of wet mixing in the step (B3), it is preferably, 20.0Sec ^-1 or more 65.0Sec ^-1 within the range in the range of 10.0 seconds ^-1 or more 70.0Sec ^-1 or less Preferably, it is in the range of 30.0 sec ⁻¹ or more and 60.0 sec ⁻¹ or less.

  In the negative electrode manufacturing paste preparation step (C), one or more selected from emulsion aqueous solutions containing an aqueous medium and an aqueous binder in the paste precursor obtained in the step (B) of preparing the paste precursor. The above-mentioned paste for producing a negative electrode is prepared by further adding the liquid component and wet mixing.

As a mixer for performing wet mixing in the paste preparation step (C) for producing a negative electrode, a planetary motion type mixer is preferably used, and a planetary motion type planetary mixer is more preferably used. By using such a mixer, it is possible to sufficiently mix while stirring at a low speed. Therefore, the dispersibility of each material which comprises the paste for negative electrode manufacture can be improved, suppressing the cutting | disconnection of the molecular chain of a thickener by stirring mixing, and suppressing aggregation of aqueous binders. And as a result, the paste for negative electrode manufacture more excellent by quality stability can be obtained.
Moreover, since the obtained paste for negative electrode manufacture is further excellent in dispersibility, when such a paste for negative electrode manufacture is used, a more uniform negative electrode active material layer can be obtained. As a result, a battery having further excellent battery characteristics can be obtained.

In this embodiment, the shear rate of the wet mixing in the negative electrode manufacturing paste preparation step (C) is not particularly limited, but is, for example, in the range of 5.0 sec ⁻¹ or more and 60.0 sec ⁻¹ or less.

  Although the mixing time of the said wet mixing in the paste preparation process (C) for negative electrode manufacture is not specifically limited, For example, they are 5 minutes or more and 60 minutes or less.

  The solid content concentration of the negative electrode production paste in the negative electrode production paste preparation step (C) can be adjusted by adjusting the concentration and addition amount of the liquid component.

The manufacturing method of the negative electrode manufacturing paste according to the present embodiment may further include a defoaming step (D): a step of vacuum defoaming. Thereby, the bubbles entrained in the paste can be removed, and the applicability of the paste can be improved.
The vacuum defoaming may be performed by removing the bubbles by applying a sealing process to the container or the shaft of the mixer, or may be performed after moving to another container.

<Battery negative electrode>
FIG. 1 is a cross-sectional view showing an example of the structure of a battery negative electrode 100 according to an embodiment of the present invention. The battery negative electrode 100 according to the present embodiment is provided on at least one surface of the current collector layer 101 and the current collector layer 101, and is formed by a solid content of the negative electrode manufacturing paste according to the present embodiment. Negative electrode active material layer 103.

As the current collector layer 101 used for manufacturing the battery negative electrode 100 according to the present embodiment, for example, a normal current collector usable for a battery can be used.
When the battery is a lithium ion battery, for example, copper, stainless steel, nickel, titanium, or an alloy thereof can be used as the negative electrode current collector, and among these, copper is particularly preferable.
Although it does not specifically limit about the shape of a collector, For example, a foil-shaped thing can be used in the range whose thickness is 0.001-0.5 mm.

  The thickness and density of the negative electrode active material layer 103 according to the present embodiment are not particularly limited because they are appropriately determined according to the intended use of the battery, and can be set according to generally known information.

<Method for producing negative electrode for battery>
Next, a method for manufacturing the battery negative electrode 100 according to this embodiment will be described.
The manufacturing method of the battery negative electrode 100 according to the present embodiment is performed by applying the negative electrode manufacturing paste obtained by the negative electrode manufacturing paste manufacturing method according to the present embodiment to the current collector layer 101 and then drying the paste. A step of forming the negative electrode active material layer 103 on the current collector layer 101 by removing the medium is included. Thereby, the negative electrode 100 for batteries excellent in adhesiveness between the current collector layer 101 and the negative electrode active material layer 103 can be stably obtained.

  That is, the battery negative electrode 100 according to this embodiment is obtained by applying the negative electrode manufacturing paste according to this embodiment on the negative electrode current collector layer 101 and drying it, and removing the aqueous medium to thereby collect the current collector layer 101. It can be obtained by forming the negative electrode active material layer 103 thereon.

  As a method for applying the negative electrode manufacturing paste according to the present embodiment on the current collector layer 101, generally known methods can be used. Examples thereof include a reverse roll method, a direct roll method, a doctor blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, a dip method, and a squeeze method.

  The negative electrode manufacturing paste according to the present embodiment may be applied to only one surface of the current collector layer 101 or may be applied to both surfaces. In the case of applying to both surfaces of the current collector layer 101, it may be applied sequentially on each side or on both sides simultaneously. Moreover, you may apply | coat to the surface of the electrical power collector layer 101 continuously or intermittently. The thickness, length and width of the coating layer can be appropriately determined according to the size of the battery.

  A generally known method can be used for drying the applied negative electrode manufacturing paste. For example, hot air, vacuum, infrared rays, far infrared rays, electron beams, and low temperature winds can be used alone or in combination. The drying temperature is, for example, in the range of 30 ° C. or higher and 350 ° C. or lower.

The battery negative electrode 100 according to the present embodiment may be pressed as necessary. As a pressing method, a generally known method can be used. For example, a die press method, a calendar press method, etc. are mentioned. Although a press pressure is not specifically limited, For example, it is the range of 0.2-3 t / cm < ² >.

  The thickness and density of the battery negative electrode 100 according to the present embodiment are not particularly limited because they are appropriately determined according to the intended use of the battery, and can be set according to generally known information.

<Battery>
Next, the battery 150 according to this embodiment will be described. FIG. 2 is a cross-sectional view showing an example of the structure of the battery 150 according to the embodiment of the present invention.

The battery 150 according to the present embodiment includes at least a positive electrode 120, an electrolyte 110, and a negative electrode 130, and the negative electrode 130 includes the negative electrode for a battery 100 according to the present embodiment. Further, the battery 150 according to the present embodiment may include a separator as necessary.
In the battery 150 according to the present embodiment, the negative electrode 130 includes the battery electrode 100 according to the present embodiment, so that powdering of the negative electrode active material layer during assembly of the battery is suppressed, and the battery quality and battery cycle are reduced. Good characteristics.
The battery 150 according to this embodiment can be manufactured according to a known method.
For example, a laminated body or a wound body can be used as the electrode. As the exterior body, a metal exterior body or an aluminum laminate exterior body can be used as appropriate. The shape of the battery may be any shape such as a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, and a flat shape.

  The positive electrode 120 of the battery can be manufactured by a known manufacturing method. For example, a paste produced by using a method such as coating / drying a positive electrode current collector with a paste containing at least a positive electrode active material and a binder, and further containing a conductive additive and a thickener as necessary. .

The positive electrode active material is not particularly limited as long as it is a normal positive electrode active material that can be used for the positive electrode of the battery. When the battery is a lithium ion battery, for example, lithium and transition metal composite oxides such as lithium nickel composite oxide, lithium cobalt composite oxide, lithium manganese composite oxide, lithium-manganese-nickel composite oxide; TiS ₂ , transition metal sulfides such as FeS and MoS ₂ ; transition metal oxides such as MnO, V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ , olivine-type lithium phosphorus oxide, and the like.
The olivine-type lithium phosphorus oxide is, for example, at least one member selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B, Nb, and Fe. It contains elements, lithium, phosphorus, and oxygen. In order to improve the characteristics of these compounds, some elements may be partially substituted with other elements.

  Among these, olivine type lithium iron phosphorus oxide, lithium cobalt composite oxide, lithium nickel composite oxide, lithium manganese composite oxide, and lithium-manganese-nickel composite oxide are preferable. These positive electrode active materials have a high working potential, a large capacity, and a large energy density. A positive electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type.

  The binder resin used for the positive electrode is appropriately selected according to the application. For example, a fluorine-based binder resin that can be dissolved in a solvent, an aqueous binder that can be dispersed in water, or the like can be used.

  The fluorine-based binder resin is not particularly limited as long as electrode molding is possible and it has sufficient electrochemical stability, and examples thereof include polyvinylidene fluoride-based resins and fluorine rubber. These fluorine-based binder resins may be used alone or in combination of two or more. Among these, a polyvinylidene fluoride resin is preferable. The fluorine-based binder resin can be used by being dissolved in a solvent such as N-methyl-pyrrolidone (NMP), for example.

  Moreover, as the water-based binder resin, the thickener, and the conductive assistant, the same materials as those constituting the negative electrode manufacturing paste according to the present embodiment can be used.

As the positive electrode current collector, aluminum, stainless steel, nickel, titanium, or an alloy thereof can be used, and among these, aluminum is particularly preferable.

Any known lithium salt may be used as the electrolyte in the battery electrolyte, and may be selected according to the type of active material. For _{example, LiClO 4, LiBF 6, LiPF} 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 Cl 10, LiAlCl 4, LiCl, LiBr, LiB (C 2 H 5) 4, CF 3 Examples include SO ₃ Li, CH ₃ SO ₃ Li, LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, and lower fatty acid carboxylate lithium.

  The solvent for dissolving the electrolyte is not particularly limited as long as it is usually used as a liquid component for dissolving the electrolyte. Ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate Carbonates such as (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC) and vinylene carbonate (VC); lactones such as γ-butyrolactone and γ-valerolactone; trimethoxymethane, 1,2-dimethoxyethane Ethers such as diethyl ether, 2-ethoxyethane, tetrahydrofuran and 2-methyltetrahydrofuran; sulfoxides such as dimethyl sulfoxide; oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane Nitrogenous compounds such as acetonitrile, nitromethane, formamide, dimethylformamide; organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate; phosphate triesters and diglymes; Sulfolanes such as sulfolane and methylsulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; sultones such as 1,3-propane sultone, 1,4-butane sultone, naphtha sultone, and the like. These may be used individually by 1 type and may be used in combination of 2 or more type.

As a separator, a porous separator is mentioned, for example. Examples of the separator include membranes, films, and nonwoven fabrics.
Examples of the porous separator include polyolefin-based porous separators such as polypropylene and polyethylene; porous separators formed of polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride hexafluoropropylene copolymer, etc. Is mentioned.

As mentioned above, although embodiment of this invention was described, these are illustrations of this invention and various structures other than the above are also employable.
Further, the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within a scope that can achieve the object of the present invention are included in the present invention.

  Hereinafter, although an example and a comparative example explain the present invention, the present invention is not limited to these.

(Example 1)
<Preparation of aqueous negative electrode production paste>
(1) Step (A)
A planetary motion type planetary mixer (pot size: 5 L) and graphite coated with amorphous carbon on the surface (average particle diameter d ₅₀ : 16 μm, specific surface area by nitrogen adsorption BET method: 3.4 m ² / g) 1500 g, carboxymethylcellulose powder (Nippon Paper's Sunrose (registered trademark) MAC series, etherification degree: 0.73, weight average molecular weight Mw: 300000 (polyethylene glycol equivalent)), 2.95 g, and conductivity As an auxiliary agent, 6.2 g of carbon black (specific surface area by nitrogen adsorption BET method: 60 m ^{2 /} g) in which primary particles of about 30 nm aggregated in a chain shape was added. Subsequently, dry mixing was performed for 20 minutes under the conditions of a shear rate of 13.1 sec ⁻¹ and a temperature of 25 ° C. to obtain a powder mixture.
Hereinafter, the average particle size _{d 50} is manufactured by Microtrac, it was measured by MT3000 device, specific surface area, Quantachrome Corporation, Inc., using a Quanta Sorb, determined by nitrogen adsorption BET method.

Here, the graphite whose surface was coated with amorphous carbon was produced as follows.
Natural graphite having an average particle diameter d ₅₀ of 16 μm and a specific surface area of 3.4 m ² / g was used as a core material.
99.0 parts by mass of this natural graphite powder and 1.0 part by mass of coal-based pitch powder were mixed in a solid phase by simple mixing using a V blender. The obtained mixed powder was put into a graphite crucible and heat-treated at 1300 ° C. for 1 hour under a nitrogen stream to obtain graphite whose surface was coated with amorphous carbon.

(2) Step (B1)
Subsequently, water was added to the planetary motion type planetary mixer in which the dry mixing step (A) was completed so that the solid content concentration of the resulting mixture (M2) was 80% by mass. Thereafter, wet mixing was performed for 20 minutes under conditions of a shear rate of 32.7 sec ⁻¹ , temperature: 25 ° C., and atmospheric pressure, and water was blended into the powder mixture to obtain a mixture (M2).

(3) Step (B2)
Next, carboxymethylcellulose powder (Sunrose (registered trademark) MAC series manufactured by Nippon Paper Industries Co., Ltd., degree of etherification: 0.73, weight average molecular weight Mw: 300,000 (in terms of polyethylene glycol)) was added to the mixture (M2) 12.58 g Then, water was added so that the solid content concentration of the resulting mixture (M3) was 63% by mass to obtain a mixture (M3).

(4) Step (B3)
Next, the mixture (M3) was wet-mixed for 30 minutes under conditions of a shear rate of 52.3 sec ⁻¹ , temperature: 25 ° C., and atmospheric pressure to obtain a paste precursor for negative electrode production.

(5) Step (C)
Next, an aqueous SBR emulsion solution having a solid content concentration of 71% by mass in which styrene-butadiene copolymer rubber (SBR) was dispersed in water as an aqueous binder resin was prepared. 77.64 g of the obtained aqueous SBR emulsion solution was added to the planetary motion type planetary mixer in which the step (B3) was completed.
Thereafter, wet mixing was performed for 15 minutes under conditions of a shear rate of 32.7 sec ⁻¹ and a temperature of 25 ° C.

(6) Step (D)
Next, vacuum defoaming was performed to obtain a paste for producing a negative electrode.
The final solid content concentration of the negative electrode manufacturing paste was adjusted to 51 mass% by adding water in the step (C) of preparing the negative electrode manufacturing paste.

<Production of negative electrode>
The obtained paste for negative electrode production was applied to both surfaces of a copper foil as a current collector layer using a die coater and dried. Next, the obtained electrode was pressed to obtain a negative electrode.

<Evaluation>
(1) Viscosity Measurement of Negative Electrode Manufacturing Paste Using a B-type viscometer (Brookfield, rotational viscometer), the viscosity of the negative electrode manufacturing paste was measured at 25 ° C. and a shear rate of 3.4 s ⁻¹ . .

(2) Peel strength test The peel strength of the obtained negative electrode was measured by the following procedure. The negative electrode was cut out over a width of 20 mm and a length of 10 cm, and one side of the negative electrode was attached to a plate on which a double-sided tape was stretched. Next, the plate was fixed, and the negative electrode was peeled off in the 90 ° direction at a speed of 100 mm / min. The peel strength (mN / mm) at that time was measured three times, and the average value was taken as the peel strength. Here, the peel strength of the negative electrode was measured on both sides of the negative electrode. Here, in Table 1, the paste was first applied, and the dried side was designated as A side, and the side opposite to the A side was designated as B side.

  The obtained evaluation results are shown in Table 1.

(Examples 2 to 4)
Table 1 shows the mixing ratio of the first thickener and the second thickener (the total amount of the first thickener and the second thickener is 100% by mass) and the solid content concentration of the mixture (M2). A water-based negative electrode producing paste was prepared and evaluated in the same manner as in Example 1 except that each value was changed to the indicated value. The obtained results are shown in Table 1, respectively.

(Comparative Example 1)
In step (A), carboxymethylcellulose powder was not added, but in step (B2), carboxymethylcellulose powder (Sunrose (registered trademark) MAC series manufactured by Nippon Paper Industries Co., Ltd., degree of etherification: 0.73, weight average molecular weight Except for adding 15.53 g of Mw: 300,000 (polyethylene glycol equivalent)), an attempt was made to produce a paste for producing an aqueous negative electrode in the same manner as in Example 1, but in this case, a large amount of aggregation of the negative electrode active material occurred, The aqueous negative electrode production paste could not be adjusted.

(Comparative Example 2)
In step (A), 15.53 g of carboxymethylcellulose powder (Nippon Paper's Sunrose (registered trademark) MAC series, degree of etherification: 0.73, weight average molecular weight Mw: 300,000 (in terms of polyethylene glycol)) was added. Then, in the step (B2), a paste for producing an aqueous negative electrode was prepared in the same manner as in Example 1 except that carboxymethylcellulose powder was not added, and each evaluation was performed. The obtained results are shown in Table 1.

DESCRIPTION OF SYMBOLS 100 Negative electrode 101 for batteries 101 Base material layer 103 Negative electrode active material layer 110 Electrolyte 120 Positive electrode 130 Negative electrode 150 Battery

Claims (23)

A step (A) of preparing a mixture (M1) containing at least the negative electrode active material and the first thickener by mixing the negative electrode active material and the first thickener;
(B) a step of preparing a paste precursor by adding one or more liquid components selected from an aqueous emulsion containing an aqueous medium and an aqueous binder to the mixture (M1) and wet-mixing the mixture (M1); ,
In the paste precursor, the liquid component is further added and wet mixed to prepare a negative electrode manufacturing paste (C);
A method for producing a paste for producing a negative electrode, comprising:
The step (B)
A step (B1) of obtaining the mixture (M2) by allowing the liquid component to be mixed with the mixture (M1);
A step (B2) of obtaining a mixture (M3) by mixing the second thickener and the liquid component in the mixture (M2);
The manufacturing method of the paste for negative electrode manufacture which contains the process (B3) which obtains the said paste precursor by kneading the said mixture (M3) at least in this order. In the manufacturing method of the paste for negative electrode manufacture of Claim 1,
In the step (A), a method for producing a paste for producing a negative electrode, wherein a plurality of powdery substances including at least the negative electrode active material and the first thickener are dry-mixed in a powder state. In the manufacturing method of the paste for negative electrode manufacture of Claim 1 or 2,
The manufacturing method of the paste for negative electrode manufacture whose said 1st thickener mixed at the said process (A) and the said 2nd thickener mixed at the said process (B2) are the same kind. In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 3,
In the step (B2), a method for producing a paste for producing a negative electrode, wherein the second thickener is mixed in a powder state. In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 4,
A method for producing a paste for producing a negative electrode, wherein the amount of the second thickener mixed is larger than the amount of the first thickener mixed. In the manufacturing method of the paste for negative electrode manufacture of Claim 5,
The paste for negative electrode production, wherein the mixing amount of the first thickener is 1% by mass or more and 45% by mass or less when the total mixing amount of the first thickener and the second thickener is 100% by mass. Manufacturing method. In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 6,
The manufacturing method of the paste for negative electrode manufacture by which the solid content concentration of the said mixture (M3) and the solid content concentration of the said paste precursor are the same in the said process (B3). In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 7,
The manufacturing method of the paste for negative electrode manufacture which sets solid content concentration of the said paste precursor in the said process (B3) lower than solid content concentration of the said mixture (M2) in the said process (B1). In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 8,
The manufacturing method of the paste for negative electrode manufacture whose solid content concentration of the said mixture (M2) in the said process (B1) is 71 mass% or more and 95 mass% or less. In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 9,
The manufacturing method of the paste for negative electrode manufacture whose solid content concentration of the said mixture (M3) in the said process (B3) is 55 to less than 75 mass%. In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 10,
Manufacturing method of producing a negative electrode paste to set a shear rate of wet mixing in the step (B3) in the range of 10.0 seconds ^-1 or more 70.0Sec ^-1 or less. In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 11,
The manufacturing method of the paste for negative electrode manufacture whose pH of the said paste for negative electrode manufacture is 6.0 or more and 8.0 or less. In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 12,
The manufacturing method of the paste for negative electrode manufacture in which the said thickener contains a cellulose water-soluble polymer. In the manufacturing method of the paste for negative electrode manufacture of Claim 13,
The manufacturing method of the paste for negative electrode manufacture whose etherification degree of the said cellulose water-soluble polymer is 0.50 or more and 1.0 or less. In the manufacturing method of the paste for negative electrode manufacture of Claim 13 or 14,
The manufacturing method of the paste for negative electrode manufacture whose weight average molecular weight Mw of the said cellulose water-soluble polymer is 100,000 or more. In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 15,
The manufacturing method of the paste for negative electrode manufacture in which the said water-system binder contains a styrene butadiene copolymer rubber. In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 16,
When the total solid content of the negative electrode manufacturing paste is 100 parts by mass,
The content of the negative electrode active material is 70 parts by mass or more and 99.97 parts by mass or less,
The total content of the first thickener and the second thickener is 0.01 parts by mass or more and 10.0 parts by mass or less,
The manufacturing method of the paste for negative electrode manufacture whose content of the said aqueous binder is 0.01 mass part or more and 10.0 mass parts or less. In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 17,
The manufacturing method of the paste for negative electrode manufacture in which the said negative electrode active material contains a carbon material. In the manufacturing method of the paste for negative electrode manufacture as described in any one of Claims 1 thru | or 18,
The manufacturing method of the paste for negative electrode manufacture which further contains the conductive support agent by which the said paste for negative electrode manufacture was comprised with the material containing a carbon material. In the manufacturing method of the paste for negative electrode manufacture according to claim 19,
The manufacturing method of the paste for negative electrode manufacture whose specific surface area by the nitrogen adsorption BET method of the said conductive support agent is 50 m < ² > / g or more.   21. A negative electrode active material layer provided on at least one surface of the current collector layer and the solid content of the paste for producing a negative electrode according to any one of claims 1 to 20 And a negative electrode for a battery. A battery comprising at least a positive electrode, an electrolyte, and a negative electrode,
A battery, wherein the negative electrode comprises the negative electrode for a battery according to claim 21.   A negative electrode manufacturing paste obtained by the method for manufacturing a negative electrode manufacturing paste according to any one of claims 1 to 20 is applied to a current collector layer and dried to remove the aqueous medium. The manufacturing method of the negative electrode for batteries including the process of forming a negative electrode active material layer on the said collector layer.

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