JP2016021391A - Conductive material fluid dispersion for electrochemical devices, slurry for electrochemical device positive electrodes, positive electrode for electrochemical devices, and electrochemical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive material fluid dispersion for electrochemical devices, which allows a conductive material to disperse well, and allows an electrochemical device to exhibit a superior output characteristic.SOLUTION: A conductive material fluid dispersion for electrochemical devices, comprises: a conductive material; an ethylene-vinyl alcohol-based polymer; and a pyrrolidone-based solvent. The conductive material fluid dispersion includes 1-9 pts.mass of the ethylene-vinyl alcohol-based polymer to 100 pts.mass of the conductive material.SELECTED DRAWING: None

Description

  The present invention relates to a conductive material dispersion for an electrochemical element, a slurry for an electrochemical element positive electrode, a positive electrode for an electrochemical element, and an electrochemical element.

  Electrochemical elements such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors are small and light, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications. . Here, for example, an electrode for a lithium ion secondary battery usually includes a current collector and an electrode mixture layer formed on the current collector. In addition to the positive electrode active material, the electrode mixture layer, for example, the positive electrode mixture layer usually contains a conductive material for improving conductivity and a binder for binding these components in the dispersion medium. The positive electrode slurry is applied on a current collector and dried.

  Here, attempts have been made to improve electrode slurries such as positive electrode slurries in order to achieve improved performance of electrochemical devices. Specifically, a conductive material dispersion liquid obtained by premixing a conductive material, a dispersant, and a dispersion medium in order to improve the dispersibility of a conductive material such as carbon black that easily aggregates and improve the performance of an electrochemical device. And an electrode active material are combined to form an electrode slurry, and a technique for forming an electrode using the electrode slurry has been proposed.

  For example, in Patent Document 1, a conductive material dispersion containing carbon black as a conductive material, a polyvinyl alcohol resin having specific properties as a dispersant, and N-methyl-2-pyrrolidone (NMP) as a dispersion medium. In addition, a dispersion having a specific relationship between the BET specific surface area of the carbon black and the addition amount of the polyvinyl alcohol resin, and further adding the addition amount of the polyvinyl alcohol resin to the carbon black within a specific range is used for the lithium ion secondary battery. It has been proposed to be used for forming an electrode mixture layer. And in patent document 1, this electrically conductive material dispersion liquid is excellent in the dispersibility and storage stability of carbon black, and uses the electrode slurry which added the electrode active material to the said dispersion liquid, and an electrode compound-material layer with low surface resistance. Has been reported to be able to form.

  Further, for example, in Patent Document 2, a conductive material dispersion containing carbon black as a conductive material, polyvinyl acetal resin as a dispersant, and NMP as a dispersion medium is used to form an electrode mixture layer of a lithium ion secondary battery. It has been proposed to use. And in patent document 2, this electrically conductive material dispersion liquid is excellent in the dispersibility and storage stability of carbon black, and internal resistance can be reduced by using the slurry for electrodes which added the electrode active material to the said dispersion liquid. It has been reported that an electrode mixture layer can be formed.

Patent No. 5454725 JP 2011-184664 A

However, in the above conventional technique, the dispersibility of the conductive material in the conductive material dispersion and the electrode slurry may be insufficient, and in addition, the dispersibility of the conductive material may be impaired due to a change in viscosity over time. It was. In the electrode mixture layer formed using such a conductive material dispersion and the electrode slurry, it is difficult to form a suitable network between the conductive materials, and the electric power using the electrode including the electrode mixture layer is used. With chemical elements, sufficient output characteristics could not be obtained.
Therefore, the above conventional technology still has room for improvement in terms of ensuring the dispersibility of the conductive material and improving the output characteristics of the electrochemical element.

Then, an object of this invention is to provide the electrically conductive material dispersion liquid for electrochemical elements which can disperse | distribute a electrically conductive material favorably and can exhibit the output characteristic excellent in the electrochemical element.
Another object of the present invention is to provide a slurry for a positive electrode for an electrochemical element that can disperse a conductive material well and exhibit excellent output characteristics for the electrochemical element.
Furthermore, the present invention provides a positive electrode for an electrochemical element that includes a positive electrode mixture layer in which a conductive material is well dispersed and can exhibit excellent output characteristics in an electrochemical element, and an electrochemical element that has excellent output characteristics. The purpose is to provide.

  The present inventors have intensively studied for the purpose of solving the above problems. Then, the present inventors use an ethylene-vinyl alcohol-based polymer (copolymer) as a dispersant in a specific blending ratio in a conductive material dispersion using a pyrrolidone-based solvent as a dispersion medium. It was found that the dispersibility and storage stability of the electroconductive material can be made excellent, and the output characteristics of the electrochemical device produced using this conductive material dispersion can be improved, and the present invention has been completed. .

  That is, the present invention aims to advantageously solve the above-mentioned problems, and the conductive material dispersion for an electrochemical element of the present invention comprises a conductive material, an ethylene-vinyl alcohol polymer, and a pyrrolidone solvent. 1 to 9 parts by mass of the ethylene-vinyl alcohol polymer per 100 parts by mass of the conductive material. Thus, if a specific amount of ethylene-vinyl alcohol polymer is used in a conductive material dispersion using a pyrrolidone solvent as a dispersion medium, the dispersibility and storage stability of the conductive material in the conductive material dispersion are improved. On the other hand, the electrochemical device manufactured using the conductive material dispersion can exhibit excellent output characteristics.

Here, in the conductive material dispersion for an electrochemical element of the present invention, the saponification degree of the ethylene-vinyl alcohol polymer is preferably 96.0 mol% or more. This is because if an ethylene-vinyl alcohol polymer having a saponification degree of 96.0 to 100 mol% is used, the storage stability of the conductive material dispersion can be further improved.
The saponification degree of the ethylene-vinyl alcohol polymer can be determined by a nuclear ceramic resonance (NMR) method.

And as for the electrically conductive material dispersion liquid for electrochemical elements of this invention, it is preferable that the ethylene content rate of the said ethylene-vinyl alcohol-type polymer is 40 mol% or more and 50 mol% or less. This is because an ethylene-vinyl alcohol polymer having an ethylene content of 40 to 50 mol% has a high conductive material dispersibility.
The ethylene content of the ethylene-vinyl alcohol polymer can be determined by a nuclear ceramic resonance (NMR) method.

  Moreover, it is preferable that the electrically conductive material dispersion liquid for electrochemical elements of the present invention further contains a fluororesin. By using a fluororesin, the adhesion between the electrode mixture layer formed from the conductive material dispersion and the current collector can be secured, and the electrical characteristics such as the output characteristics of the electrochemical element can be further improved. It is.

  In addition, the conductive material dispersion for an electrochemical element of the present invention preferably contains 10 parts by mass or more and 200 parts by mass or less of the fluororesin per 100 parts by mass of the conductive material. By setting the blending amount of the fluororesin to 10 to 200 parts by mass per 100 parts by mass of the conductive material, the adhesion between the electrode mixture layer formed from the conductive material dispersion and the current collector is sufficiently improved, and electrochemical This is because electrical characteristics such as output characteristics of the element can be secured at a high level.

Furthermore, in the conductive material dispersion for an electrochemical element of the present invention, the viscosity of the 10 mass% N-methyl-2-pyrrolidone solution of the fluororesin is preferably 10 mPa · s or more and 1800 mPa · s or less. By using a fluororesin having a viscosity of 10 mass% NMP solution of 10 to 1800 mPa · s, it is possible to further improve the adhesion between the electrode mixture layer formed from the conductive material dispersion and the current collector, The conductive material dispersibility of the ethylene-vinyl alcohol polymer is ensured. As a result, electrical characteristics such as output characteristics of the electrochemical element can be secured at a high level.
In addition, the viscosity of the 10 mass% NMP solution of a fluororesin can be measured using a B-type viscometer under the conditions of a temperature of 25 ° C., a rotation speed of 60 rpm, and a rotation time of 60 seconds.

  Moreover, the slurry for electrochemical element positive electrodes of this invention is characterized by including one of the above-mentioned electroconductive element dispersions for electrochemical elements and a positive electrode active material. In the positive electrode slurry prepared using any of the conductive material dispersions described above, the conductive material is well dispersed, and the positive electrode slurry is excellent in storage stability. The state can be maintained for a long time. Moreover, if the positive electrode prepared using the said slurry for positive electrodes is used, the output characteristic excellent in the electrochemical element can be exhibited.

  Moreover, the positive electrode for electrochemical devices of this invention is equipped with the positive electrode compound-material layer prepared using the above-mentioned slurry for positive electrodes of electrochemical devices on a collector. A positive electrode including a positive electrode mixture layer formed from the above-described positive electrode slurry can exhibit excellent output characteristics in an electrochemical element.

  Moreover, the electrochemical element of this invention is provided with the above-mentioned positive electrode for electrochemical elements. An electrochemical element provided with the above-mentioned positive electrode for an electrochemical element exhibits excellent output characteristics.

ADVANTAGE OF THE INVENTION According to this invention, the electrically conductive material can be disperse | distributed favorably and the electrically conductive element dispersion liquid for electrochemical elements which can exhibit the output characteristic excellent in the electrochemical element can be provided.
Moreover, according to this invention, the slurry for electrochemical element positive electrodes which can disperse | distribute a electrically conductive material favorably and can exhibit the output characteristic excellent in the electrochemical element can be provided.
Furthermore, according to the present invention, the positive electrode for an electrochemical element that has an electrode mixture layer in which a conductive material is well dispersed and can exhibit excellent output characteristics in an electrochemical element, and electrochemical that has excellent output characteristics An element can be provided.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the electroconductive element-use conductive material dispersion liquid of the present invention is used as a material for producing an electrochemical element electrode slurry, preferably an electrochemical element positive electrode slurry. And the slurry for electrochemical element positive electrodes of this invention is formed using the electrically conductive material dispersion liquid for electrochemical elements of this invention. In addition, the positive electrode for electrochemical devices of the present invention is characterized by including a positive electrode mixture layer formed using the slurry for positive electrodes of electrochemical devices of the present invention. Moreover, the electrochemical element of this invention is equipped with the positive electrode for electrochemical elements of this invention, It is characterized by the above-mentioned.

(Conductive material dispersion for electrochemical devices)
The conductive material dispersion for an electrochemical element of the present invention contains a conductive material and an ethylene-vinyl alcohol polymer in a pyrrolidone solvent, and optionally further contains a fluororesin. And the electrically conductive material dispersion liquid for electrochemical elements of the present invention is characterized in that the blending amount of the ethylene-vinyl alcohol polymer is 1 to 9 parts by mass per 100 parts by mass of the electrically conductive material.
As described above, the conductive material dispersion containing a specific amount of the ethylene-vinyl alcohol polymer is excellent in the dispersibility of the conductive material, and further, the viscosity change with time is suppressed, and the excellent conductive material dispersion state is maintained for a long time. can do. Moreover, the electrode provided with the electrode compound-material layer formed using the said electrically-conductive material dispersion liquid can exhibit the output characteristic excellent in the electrochemical element.

<Conductive material>
The conductive material is for ensuring electrical contact between the electrode active materials in the electrode mixture layer. The conductive material used in the conductive material dispersion of the present invention is not particularly limited, and carbon black (for example, acetylene black, ketjen black (registered trademark), furnace black, etc.), single-walled or multi-walled carbon nanotubes (Multi-walled carbon nanotubes include cup-stacked types), carbon nanohorns, vapor-grown carbon fibers, milled carbon fibers obtained by crushing polymer fibers after firing, single-layer or multilayer graphene, and nonwoven fabrics made of polymer fibers A conductive carbon material such as a carbon non-woven sheet obtained as well as various metal fibers or foils can be used. These can be used individually by 1 type or in combination of 2 or more types. Among these, a conductive carbon material is preferable because it is excellent in chemical stability. Also, from the viewpoint of increasing the contact frequency between adjacent conductive carbon materials, achieving highly efficient electron transfer while forming a stable conductive path, and exhibiting excellent conductivity, carbon black and fibers A conductive carbon material that is in the form of a sheet or a sheet is more preferable.
Here, in the present invention, that the conductive carbon material is “fibrous” means that the aspect ratio of the conductive carbon material measured by a transmission electron microscope (TEM) is 10 or more, and the fibrous conductivity. Examples of the carbon material include the single-walled or multi-walled carbon nanotubes, carbon nanohorns, vapor-grown carbon fibers, and milled carbon fibers described above.
Further, in the present invention, the conductive carbon material being “sheet-like” means that the conductive carbon material has a structure spreading in a plane, and the sheet-like conductive carbon material includes, for example, the single layer described above. Or a multilayer graphene, a carbon nonwoven fabric sheet, etc. are mentioned. The sheet-like conductive carbon material having a structure extending in a planar shape does not include a fibrous conductive carbon material.

The average particle size of carbon black is preferably 10 nm or more, more preferably 15 nm or more, still more preferably 20 nm or more, preferably 100 nm or less, more preferably 70 nm or less, and even more preferably 50 nm or less. If the average particle size of the carbon black is within the above range, the storage stability of the conductive material dispersion is improved while further improving the dispersibility of the conductive material carbon black, and the output characteristics of the electrochemical device are further improved. Can be made.
In the present invention, the “average particle diameter of carbon black” means the particle diameter of 100 carbon black particles randomly selected using TEM (the length of a line segment connecting two points on the outer edge of each particle). Can be obtained by measuring the maximum length).

The specific surface area of the conductive material is preferably 20 m ² / g or more, more preferably 35 m ² / g or more, preferably 1000 m ² / g or less, more preferably 800 m ² / g or less, and still more preferably 500 m ² / g. Hereinafter, it is particularly preferably 100 m ² / g or less, most preferably 60 m ² / g or less. If the specific surface area of the conductive material is within the above range, the storage stability of the conductive material dispersion can be improved while further improving the dispersibility of the conductive material, and the output characteristics of the electrochemical device can be further improved.
In the present invention, the “specific surface area of the conductive material” is a BET specific surface area by a nitrogen adsorption method, and can be measured in accordance with ASTM D3037-81.

The density of the conductive material is preferably 0.01 g / cm ³ or more, more preferably 0.02 g / cm ³ or more, preferably 0.5 g / cm ³ or less, more preferably 0.3 g / cm ³ or less. More preferably, it is 0.2 g / cm ³ or less. When the density of the conductive material is within the above range, scattering of the conductive material during preparation of the conductive material dispersion is suppressed, and workability can be ensured. Further, the storage stability of the conductive material dispersion, the coating properties of the electrode slurry, and the output characteristics of the electrochemical device can be further improved.
In the present invention, the “density of the conductive material” is a bulk density and can be measured according to JIS Z 8901.

<Ethylene-vinyl alcohol polymer>
The ethylene-vinyl alcohol polymer (EVOH) comprises an ethylene structural unit represented by the formula: —CH ₂ —CH ₂ — and a vinyl alcohol structural unit represented by the formula: —CH ₂ —CH (OH) —. It is a copolymer having a main repeating unit, and can function as a dispersant for dispersing the conductive material in the conductive material dispersion of the present invention. In EVOH, the total of the ratio of the number of ethylene structural units (ethylene content) to the number of all repeating units and the ratio of the number of vinyl alcohol structural units is preferably 80 mol% or more, more preferably 90 mol%. As described above, it is particularly preferably 100 mol%.
In addition, EVOH may be used independently and may use 2 or more types together.

Although the production method of EVOH is not particularly limited, EVOH is obtained by saponifying a copolymer of ethylene and a fatty acid vinyl ester with an alkali catalyst or the like. Examples of the fatty acid vinyl ester copolymerized with ethylene include vinyl acetate, vinyl propionate, and vinyl pivalate, and vinyl acetate is preferred. Further, the saponification method is not particularly limited.
EVOH may be modified by a known method after saponifying a copolymer of ethylene and a fatty acid vinyl ester with an alkali catalyst or the like.

  EVOH saponification degree (that is, the ratio of hydrolysis (saponification) of fatty acid vinyl ester structural units) is from 96.0 mol% to 100% from the viewpoint of improving the storage stability of the conductive material dispersion. Preferably, it is 97.0 mol% or more and 100% or less.

  The ethylene content of EVOH is preferably 40 mol% or more, more preferably 42 mol% or more, further preferably 43 mol% or more, and preferably 50 mol% or less. 48 mol% or less, more preferably 45 mol% or less. When the ethylene content is in the above range, the conductive material dispersibility of EVOH can be more satisfactorily exhibited.

  The conductive material dispersion of the present invention needs to contain 1 to 9 parts by mass of EVOH per 100 parts by mass of the conductive material, preferably 5 parts by mass or more, more preferably 7 parts by mass or more. . A conductive material cannot be disperse | distributed favorably as the compounding quantity of EVOH is less than 1 mass part per 100 mass parts of electrically conductive material. As a result, in the electrode mixture layer formed using the conductive material dispersion liquid, the dispersibility of the conductive material is reduced, and electrical characteristics such as output characteristics are obtained without forming a suitable network between the conductive materials. descend. On the other hand, when the blending amount of EVOH is more than 9 parts by mass per 100 parts by mass of the conductive material, an effect of improving dispersibility commensurate with the increase in the blending amount of EVOH due to an increase in the viscosity of the conductive material dispersion liquid can be obtained. In addition, in an electrochemical element having an electrode including an electrode mixture layer formed from a conductive material dispersion, internal resistance increases and electrical characteristics such as output characteristics decrease.

<Fluorine resin>
The conductive material dispersion of the present invention may optionally contain a fluororesin. By using a fluororesin that can function as a binder, the adhesion between the electrode mixture layer formed from the conductive material dispersion and the current collector is secured, and the electrical characteristics of the electrochemical device such as output characteristics Can be improved.
In addition, although the said EVOH also exhibits binding property, as mentioned above, there is a limit to the blending amount of EVOH from the viewpoint of securing both dispersibility and electrical characteristics. Therefore, in the conductive material dispersion of the present invention, it is preferable to secure the adhesion between the electrode mixture layer and the current collector by using a fluororesin that can function as a binder in addition to EVOH.

A fluororesin is a polymer containing a fluorine-containing monomer unit. In the present specification, “comprising a monomer unit” means “a repeating unit derived from a monomer is contained in a polymer obtained using the monomer”.
Specifically, as the fluororesin, a homopolymer or copolymer of one or more fluorine-containing monomers, one or more fluorine-containing monomers and a monomer not containing fluorine (hereinafter referred to as “ And a copolymer with a "non-fluorine-containing monomer").
In addition, the ratio of the fluorine-containing monomer unit in a fluororesin is 70 mass% or more normally, Preferably it is 80 mass% or more. Moreover, the ratio of the fluorine-free monomer unit in the fluororesin is usually 30% by mass or less, preferably 20% by mass or less.

  Here, examples of the fluorine-containing monomer that can form a fluorine-containing monomer unit include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, vinyl trifluoride chloride, vinyl fluoride, and perfluoroalkyl vinyl ether. It is done. Among these, as the fluorine-containing monomer, vinylidene fluoride is preferable.

  Examples of the fluorine-free monomer that can form a fluorine-free monomer unit include a fluorine-free monomer copolymerizable with the fluorine-containing monomer, such as ethylene, propylene, and 1-butene. 1-olefin; aromatic vinyl compounds such as styrene, α-methylstyrene, pt-butylstyrene, vinyltoluene, chlorostyrene; unsaturated nitrile compounds such as (meth) acrylonitrile; methyl (meth) acrylate, ( (Meth) acrylic acid ester compounds such as (meth) butyl acrylate and (meth) acrylic acid 2-ethylhexyl; (meth) such as (meth) acrylamide, N-methylol (meth) acrylamide and N-butoxymethyl (meth) acrylamide Acrylamide compounds; (meth) acrylic acid, itaconic acid, fumaric acid, crotonic acid, Vinyl compounds containing carboxyl groups such as oleic acid; epoxy group-containing unsaturated compounds such as allyl glycidyl ether and glycidyl (meth) acrylate; amino such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate Group-containing unsaturated compounds; sulfonic acid group-containing unsaturated compounds such as styrene sulfonic acid, vinyl sulfonic acid and (meth) allyl sulfonic acid; sulfate group-containing unsaturated compounds such as 3-allyloxy-2-hydroxypropanesulfuric acid; ) Phosphoric acid group-containing unsaturated compounds such as acrylic acid-3-chloro-2-phosphate and 3-allyloxy-2-hydroxypropanephosphoric acid.

As the fluororesin, a polymer using vinylidene fluoride as a fluorine-containing monomer and a polymer using vinyl fluoride as a fluorine-containing monomer are preferable, and vinylidene fluoride is used as the fluorine-containing monomer. More preferred is a polymer.
Specifically, as the fluororesin, a homopolymer of vinylidene fluoride (polyvinylidene fluoride), a copolymer of vinylidene fluoride and hexafluoropropylene, and polyvinyl fluoride are preferable, and polyvinylidene fluoride (PVDF) is more preferable. preferable.
In addition, the fluororesin mentioned above may be used independently and may use 2 or more types together.

  Here, the viscosity of the solution in which the fluororesin is dissolved in NMP at a concentration of 10% by mass is preferably 10 mPa · s or more, more preferably 100 mPa · s or more, preferably 1800 mPa · s or less, more preferably 1300 mPa · s. s or less, more preferably 500 mPa · s or less. When the viscosity of the 10 mass% NMP solution of the fluororesin is 10 mPa · s or more, the adhesion between the electrode mixture layer formed from the conductive material dispersion and the current collector can be improved, and 1800 mPa · s. By being below, the dispersibility of a conductive material is not impaired by the viscosity of a conductive material dispersion rising excessively. And when the viscosity of the 10 mass% NMP solution of fluororesin is in the above-mentioned range, the electrochemical element having an electrode comprising an electrode mixture layer formed from a conductive material dispersion using the fluororesin, Electrical characteristics such as output characteristics can be improved.

Here, the manufacturing method of the fluororesin mentioned above is not specifically limited, For example, any methods, such as solution polymerization method, suspension polymerization method, block polymerization method, and emulsion polymerization method, can be used.
As the polymerization method, addition polymerization such as ionic polymerization, radical polymerization, living radical polymerization and the like can be used. Moreover, as a polymerization initiator, a known polymerization initiator can be used.

  The fluororesin is used for the preparation of a conductive material dispersion in the state of a dispersion or a solution dissolved in a dispersion medium. The dispersion medium of the fluororesin used for the preparation of the conductive material dispersion is not particularly limited as long as the fluororesin can be uniformly dispersed or dissolved, and water or an organic solvent can be used. It is preferable to use it. In addition, as an organic solvent, it does not specifically limit, The pyrrolidone type solvent used as a dispersion medium of the electrically conductive material dispersion liquid of this invention can be used.

The conductive material dispersion of the present invention preferably contains 10 parts by mass or more, preferably 200 parts by mass or less, more preferably 120 parts by mass or less, and still more preferably 50 parts by mass, per 100 parts by mass of the conductive material. Includes: When the blending amount of the fluororesin is 10 parts by mass or more per 100 parts by mass of the conductive material, the adhesion between the electrode mixture layer formed from the conductive material dispersion and the current collector can be improved. On the other hand, in the electrochemical element having an electrode including an electrode mixture layer formed from the conductive material dispersion, the amount of the fluororesin is less than 200 parts by mass per 100 parts by mass of the conductive material. An increase in internal resistance due to excess is suppressed, and electrical characteristics such as output characteristics can be ensured. In addition, the viscosity of the conductive material dispersion does not become excessively high, and the preparation of the electrode slurry is easy, and the coating property of the electrode slurry on the current collector is improved. Furthermore, the dispersibility of the conductive material in the conductive material dispersion can be ensured.
In the conductive material dispersion of the present invention, the proportion of the amount of fluororesin in the total amount of EVOH and fluororesin is preferably 65% by mass or more, more preferably 70% by mass or more, preferably Is 95% by mass or less, more preferably 90% by mass or less. Since the ratio of the fluororesin in the total amount of EVOH and fluororesin is within the above range, the balance between the binding ability obtained by EVOH and fluororesin and the dispersibility of the conductive material obtained by EVOH becomes good, and the conductivity To further improve the electrical characteristics such as output characteristics of an electrochemical device having an electrode having an electrode mixture layer formed from the conductive material dispersion, the storage stability of the conductive material dispersion, and the conductive material dispersion Can do.

<Pyrrolidone solvent>
In the conductive material dispersion of the present invention, a pyrrolidone solvent is used as a dispersion medium. This is because the pyrrolidone-based solvent has a high solubility of EVOH, so that the conductive material dispersibility of EVOH can be sufficiently exhibited. Specific examples of the pyrrolidone solvent include N-methyl-2-pyrrolidone (NMP) and N-ethyl-2-pyrrolidone (NEP). Among these, NMP is preferable from the viewpoint of solubility of the fluororesin.
These pyrrolidone solvents may be used alone or in combination of two or more.

<Method for preparing conductive material dispersion>
When the conductive material, EVOH, an arbitrary fluororesin, and a pyrrolidone-based solvent are mixed to obtain a conductive material dispersion, the mixing method is not particularly limited. For example, general mixing such as disper, mill, kneader, etc. An apparatus can be used. For example, when using a disper, it is preferable to stir at 1000 rpm to 5000 rpm for 5 minutes to 60 minutes.
Further, in obtaining the conductive material dispersion liquid, the mixing procedure is not particularly limited. For example, (A) EVOH is dissolved in a pyrrolidone solvent, and then the conductive material is added and mixed using the above-described mixing apparatus and mixing conditions. Alternatively, (B) the conductive material, EVOH, and pyrrolidone-based solvent may be mixed together using the above-described mixing apparatus and mixing conditions. Among these, the mixing procedure (A) is preferable.
Further, when a fluororesin is added to the conductive material dispersion, the conductive material, EVOH and pyrrolidone solvent are mixed, for example, from the viewpoint of further improving the dispersibility of the conductive material and the storage stability of the conductive material dispersion. It is preferable to add a fluororesin after premixing with an apparatus and mixing conditions. And after adding a fluororesin, it is preferable to further mix, for example with the above-mentioned mixing apparatus and mixing conditions. Prior to the addition of fluororesin, by mixing conductive material, EVOH and pyrrolidone solvent, EVOH as a dispersant can be preferentially adsorbed on the conductive material, and EVOH's conductive material dispersibility is fully demonstrated. It is because it can be made. In addition, you may add a fluororesin in the preparation stage of the slurry for electrochemical element positive electrodes.
The TI value (thixotropic index value) of the obtained conductive material dispersion is preferably 0.80 or more, more preferably 0.95 or more, and preferably 3.50 or less, More preferably, it is 2.0 or less. If the TI value is within the above range, the coating property of the electrode slurry can be improved, and the electrical characteristics such as the output characteristics of the electrochemical element can be further enhanced.
Here, the TI value is obtained by using a B-type viscometer, except that the rotation speed is 6 rpm with respect to the viscosity η60 of the conductive material dispersion measured at a temperature of 25 ° C., a rotation speed of 60 rpm, and a rotation time of 60 seconds. It can be determined as the ratio (η6 / η60) of the viscosity η6 of the conductive material dispersion measured in the same manner as η60.

(Slurry for electrochemical element positive electrode)
The slurry for an electrochemical element positive electrode of the present invention contains the above-described conductive material dispersion for an electrochemical element and a positive electrode active material. That is, it contains a conductive material, EVOH, a positive electrode active material, a pyrrolidone-based solvent, and optionally a fluororesin.
As described above, the electrode mixture layer formed from the slurry for the secondary battery positive electrode containing the above-described electroconductive element-use conductive material dispersion liquid has a preferable conductive material because the conductive material is well dispersed therein. A network between them is formed. Moreover, in the said electrode compound-material layer, the increase in internal resistance is suppressed. Therefore, an electrochemical device having a positive electrode including such an electrode mixture layer is excellent in electrical characteristics such as output characteristics.

<Positive electrode active material>
As a positive electrode active material mix | blended with the slurry for electrochemical element positive electrodes, it is not specifically limited, A known positive electrode active material can be used.
For example, a positive electrode active material used for a lithium ion secondary battery is not particularly limited, and lithium-containing cobalt oxide (LiCoO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium-containing nickel oxide (LiNiO _2). ), Co—Ni—Mn lithium-containing composite oxide, Ni—Mn—Al lithium-containing composite oxide, Ni—Co—Al lithium-containing composite oxide, olivine-type lithium iron phosphate (LiFePO ₄ ), olivine Type lithium lithium phosphate (LiMnPO ₄ ), Li _{1 + x} Mn _2−x O ₄ (0 <X <2), an excess lithium spinel compound, Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ , LiNi _0.5 Mn _1.5 O _{4 and the} like.
Further, for example, a positive electrode active material used for a lithium ion capacitor or an electric double layer capacitor is not particularly limited, and includes an allotrope of carbon. Specific examples of the allotrope of carbon include activated carbon, polyacene, carbon whisker, and graphite, and these powders or fibers can be used.

Among the above, from the viewpoint of improving battery capacity and the like in a lithium ion secondary battery, lithium-containing cobalt oxide (LiCoO ₂ ), lithium-containing nickel oxide (LiNiO ₂ ), and Co—Ni—Mn are used as the positive electrode active material. Lithium-containing composite oxide, lithium-containing composite oxide of Ni—Co—Al, Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ or LiNi _0.5 Mn _1.5 O ₄ Is preferably used.
The particle size of the positive electrode active material is not particularly limited, and can be the same as that of a positive electrode active material conventionally used.
The slurry for an electrochemical device positive electrode of the present invention preferably contains 1000 parts by mass or more, more preferably 2000 parts by mass or more, preferably 10,000 parts by mass or less, more preferably 100 parts by mass or more of the positive electrode active material per 100 parts by mass of the conductive material. Including 5000 parts by mass or less.

<Other ingredients>
In addition to the above-described components, the electrochemical element positive electrode slurry includes, for example, a binder other than a fluororesin, a viscosity modifier, a reinforcing material, an antioxidant, and an electrolyte additive having a function of suppressing decomposition of the electrolyte You may mix components, such as. As these other components, known ones can be used. Moreover, you may mix | blend these other components with the electrically conductive material dispersion liquid for electrochemical elements of this invention mentioned above.

<Method for preparing slurry for electrochemical element positive electrode>
In the conductive material dispersion, the above-described positive electrode active material, and optionally, other components and an additional dispersion medium are mixed to obtain a slurry for an electrochemical device positive electrode. For example, a general mixing apparatus such as a disper, a mill, or a kneader can be used. For example, when using a disper, it is preferable to stir at 1000 rpm to 5000 rpm for 5 minutes to 120 minutes.

(Positive electrode for electrochemical devices)
The positive electrode for electrochemical devices of the present invention can be produced using the slurry for positive electrodes of electrochemical devices of the present invention.
And the positive electrode for electrochemical devices of the present invention comprises a current collector and a positive electrode mixture layer formed on the current collector. The positive electrode mixture layer includes at least a positive electrode active material, a conductive material, and And EVOH. In addition, the positive electrode active material, the conductive material, and EVOH contained in the positive electrode mixture layer are those contained in the electrochemical device conductive material dispersion and the electrochemical device positive electrode slurry of the present invention, A suitable abundance ratio of each of these components is the same as a preferred abundance ratio of each component in the electroconductive element conductive material dispersion and the electrochemical element positive electrode slurry of the present invention.

  And since the electrically conductive material is disperse | distributing favorable in the positive mix layer formed from the slurry for electrochemical element positive electrodes mentioned above, the network between suitable electrically conductive materials is formed. In addition, the positive electrode mixture layer is suppressed from increasing in internal resistance. Therefore, the electrochemical device having the positive electrode for an electrochemical device of the present invention having such a positive electrode mixture layer is excellent in electrical characteristics such as output characteristics.

<Method for producing positive electrode for electrochemical device>
The manufacturing method of the positive electrode for electrochemical devices of this invention includes the process of apply | coating the slurry for electrochemical device positive electrodes of this invention to at least one surface of a collector, and drying, and forming a positive mix layer. More specifically, the manufacturing method includes a step of applying the electrochemical device positive electrode slurry to at least one surface of the current collector (application step), and an electrochemical device applied to at least one surface of the current collector. And a step of drying the positive electrode slurry to form a positive electrode mixture layer on the current collector (drying step).

[Coating process]
The method for coating the electrochemical device positive electrode slurry on the current collector is not particularly limited, and a known method can be used. Specifically, as a coating method, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method, or the like can be used. At this time, the electrochemical device positive electrode slurry may be applied to only one surface of the current collector, or may be applied to both surfaces. The thickness of the slurry film on the current collector after application and before drying can be appropriately set according to the thickness of the positive electrode mixture layer obtained by drying.

  Here, as the current collector on which the slurry for the electrochemical device positive electrode is applied, a material having electrical conductivity and electrochemical durability is used. Specifically, a current collector made of aluminum or an aluminum alloy can be used as the current collector. At this time, aluminum and an aluminum alloy may be used in combination, or different types of aluminum alloys may be used in combination. Aluminum and aluminum alloys are excellent current collector materials because they have heat resistance and are electrochemically stable.

[Drying process]
The method for drying the slurry for the electrochemical device positive electrode on the current collector is not particularly limited, and a known method can be used, for example, drying with hot air, hot air, low-humidity air, vacuum drying, infrared rays, electron beam, etc. And a drying method by irradiation. Thus, by drying the slurry for the electrochemical device positive electrode on the current collector, a positive electrode composite material layer is formed on the current collector, and the positive electrode for an electrochemical device comprising the current collector and the positive electrode composite material layer is provided. Can be obtained.

Note that after the drying step, the positive electrode mixture layer may be subjected to pressure treatment using a die press or a roll press. By the pressure treatment, the adhesion between the positive electrode mixture layer and the current collector can be improved.
Furthermore, when the positive electrode mixture layer contains a curable polymer, the polymer is preferably cured after the positive electrode mixture layer is formed.

(Electrochemical element)
The electrochemical device of the present invention is not particularly limited, and is a lithium ion secondary battery, a lithium ion capacitor or an electric double layer capacitor, preferably a lithium ion secondary battery. And the electrochemical element of this invention is equipped with the positive electrode for electrochemical elements of this invention, It is characterized by the above-mentioned. Such an electrochemical element is excellent in electrical characteristics such as output characteristics.

  Here, below, the structure of the lithium ion secondary battery as an example of the electrochemical element of this invention is demonstrated. This lithium ion secondary battery usually includes a negative electrode, an electrolytic solution, and a separator in addition to the positive electrode for an electrochemical element of the present invention. Hereafter, each said structure is demonstrated.

<Negative electrode>
As a negative electrode of a lithium ion secondary battery, a known negative electrode used as a negative electrode for a lithium ion secondary battery can be used. Specifically, as the negative electrode, for example, a negative electrode made of a thin plate of metallic lithium or a negative electrode formed by forming a negative electrode mixture layer on a current collector can be used.
In addition, as a collector, what consists of metal materials, such as iron, copper, aluminum, nickel, stainless steel, titanium, a tantalum, gold | metal | money, platinum, can be used. As the negative electrode mixture layer, a layer containing a negative electrode active material and a binder can be used. Furthermore, the binder is not particularly limited, and any known material can be used.

<Electrolyte>
As the electrolytic solution, an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. For example, a lithium salt is used as the supporting electrolyte. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi , (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, and the like. Among them, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li are preferable, and LiPF ₆ is particularly preferable because it is easily dissolved in a solvent and exhibits a high degree of dissociation. In addition, electrolyte may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. Usually, the lithium ion conductivity tends to increase as the supporting electrolyte having a higher degree of dissociation is used, so that the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.

The organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte. For example, dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), Carbonates such as butylene carbonate (BC) and methyl ethyl carbonate (EMC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide Etc. are preferably used. Moreover, you may use the liquid mixture of these solvents. Among them, it is preferable to use carbonates because they have a high dielectric constant and a wide stable potential region, and it is more preferable to use a mixture of ethylene carbonate and ethyl methyl carbonate.
In addition, the density | concentration of the electrolyte in electrolyte solution can be adjusted suitably, for example, it is preferable to set it as 0.5-15 mass%, it is more preferable to set it as 2-13 mass%, and it shall be 5-10 mass%. Is more preferable. Further, known additives such as fluoroethylene carbonate and ethyl methyl sulfone may be added to the electrolytic solution.

<Separator>
As a separator, it does not specifically limit, For example, the thing of Unexamined-Japanese-Patent No. 2012-204303 can be used. Among these, the thickness of the entire separator can be reduced, thereby increasing the ratio of the electrode active material in the lithium ion secondary battery and increasing the capacity per volume. A microporous membrane made of a resin of the type (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferable.

<Method for producing lithium ion secondary battery>
The lithium ion secondary battery according to the present invention includes, for example, a positive electrode and a negative electrode that are overlapped via a separator and wound into a battery container according to the battery shape as necessary. It can manufacture by inject | pouring electrolyte solution into and sealing. In order to prevent an increase in pressure inside the secondary battery, overcharge / discharge, and the like, a fuse, an overcurrent prevention element such as a PTC element, an expanded metal, a lead plate, and the like may be provided as necessary. The shape of the secondary battery may be any of, for example, a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, and a flat shape.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the following description, “%” and “part” representing amounts are based on mass unless otherwise specified.
In the examples and comparative examples, the viscosity and TI value of the conductive material dispersion, the dispersibility of the conductive material in the conductive material dispersion, the storage stability of the conductive material dispersion, and the output characteristics of the lithium ion secondary battery are respectively Evaluation was made using the following method.

<Viscosity of conductive material dispersion>
The viscosity η1 of the conductive material dispersion immediately after preparation was measured at a temperature of 25 ° C., a rotation speed of 60 rpm, and a rotation time of 60 seconds using a B-type viscometer, and evaluated according to the following criteria. The smaller the viscosity of the conductive material dispersion, the easier the preparation of the positive electrode slurry containing the conductive material dispersion, and the better the coating property of the resulting positive electrode slurry on the current collector.
A: η1 is less than 400 mPa · s.
B: η1 is 400 mPa · s or more and less than 500 mPa · s.
C: η1 is 500 mPa · s or more and less than 600 mPa · s.
D: η1 is 600 mPa · s or more.
<TI value of conductive material dispersion>
For the conductive material dispersion immediately after the preparation, the viscosity η6 was measured using a B-type viscometer under the conditions of a temperature of 25 ° C., a rotation speed of 6 rpm, and a rotation time of 60 seconds. The above η1 was η60, and the TI value (η6 / η60) was calculated.
<Dispersibility of conductive material in conductive material dispersion>
Using a light scattering type particle size distribution meter (manufactured by Shimadzu Corporation, SALD), the dispersed particle size of the conductive material in the conductive material dispersion immediately after preparation was measured, and the volume average particle size D50 was determined. And the dispersibility of the electrically conductive material was evaluated according to the following criteria. As the volume average particle diameter D50 is smaller, the conductive material is not aggregated, and the dispersibility of the conductive material in the conductive material dispersion is better.
A: Volume average particle diameter D50 is less than 5 μm.
B: The volume average particle diameter D50 is 5 μm or more and less than 10 μm.
C: Volume average particle diameter D50 is 10 μm or more.
<Storage stability of conductive material dispersion>
The obtained conductive material dispersion was stored in a 25 ° C. environment for 30 days, and the viscosity η2 was measured in the same manner as in the above η1, and the viscosity change Δη (%) = (| η1-η2 | / η1) X100 was determined. Then, the storage stability of the conductive material dispersion was evaluated according to the following criteria. It shows that the smaller the viscosity change Δη is, the more stable the viscosity of the conductive material dispersion liquid is, and the better the dispersion state of the conductive material can be maintained.
A: Viscosity change Δη is less than 10%.
B: The viscosity change Δη is 10% or more and less than 30%.
C: Viscosity change Δη is 30% or more.
<Output characteristics of lithium ion secondary battery>
The manufactured laminated lithium ion secondary battery was charged at a constant current at a current of 140 mA until the voltage reached 4.2 V in a 25 ° C. environment, and was charged at a voltage of 4.2 V until the charging current reached 14 mA. . Subsequently, constant current discharge was performed until the battery voltage became 3 V at a current of 140 mA to obtain an initial capacity.
The laminated lithium ion secondary battery whose initial capacity was measured was charged at a constant current until the battery voltage was 4.2 V at 0.2 C in an environment of 25 ° C., and the charging current was 0.02 C at a voltage of 4.2 V. Until constant voltage charging. Subsequently, constant current discharge was performed until the battery voltage reached 3.0 V at a current of 2 C, to obtain a 2 C capacity. A value of {(2C capacity) / (initial capacity)} × 100 (%) was used as an output characteristic, and evaluation was performed according to the following criteria. The higher this value, the better the initial output characteristics, that is, the smaller the internal resistance.
A: The output characteristic is 90% or more.
B: Output characteristics are 87% or more and less than 90%.
C: The output characteristic is 84% or more and less than 87%.
D: The output characteristic is 80% or more and less than 84%.
E: The output characteristic is less than 80%.

Example 1
<Preparation of conductive material dispersion for electrochemical device>
In a plastic container, 8 parts of EVOH1 (ethylene-vinyl alcohol polymer having an ethylene content of 44 mol% and a saponification degree of 98.5 mol%) and NMP as a pyrrolidone solvent to a solid content concentration of 5% The EVOH 1 was dissolved in NMP by shaking. Then, this NMP solution of EVOH1 and carbon black α (manufactured by Denki Kagaku Kogyo Co., Ltd., HS-100, acetylene black, average particle size: 48 nm, specific surface area: 39 m ² / g, density: 0.00. 15 g / cm ³ ) 100 parts and NMP as a solvent were mixed to prepare a solid concentration of 14%. Subsequently, it stirred for 30 minutes at 2000 rpm using the disper (made by IKA).

  Then, after the above stirring, PVDF1 as a fluororesin (manufactured by Arkema Co., Ltd., KYNAR (registered trademark) 741, viscosity of 10% NMP solution: 300 mPa · s) was added in an amount of 20 parts by solid content, NMP as a solvent was added, The concentration was adjusted to 15%. Subsequently, it stirred for 30 minutes at 2000 rpm using the disper, and prepared the electrically conductive material dispersion containing carbon black, EVOH1, PVDF1, and NMP. The viscosity and TI value of the conductive material dispersion immediately after preparation were measured, and the dispersibility of the conductive material in the conductive material dispersion and the storage stability of the conductive material dispersion were evaluated. The results are shown in Table 1.

<Production of slurry for positive electrode and positive electrode>
To the obtained conductive material dispersion, 2000 parts of LiCoO ₂ as a positive electrode active material was added, and stirred at 2500 rpm for 30 minutes using a disper to obtain a positive electrode slurry.
This positive electrode slurry was applied with a comma coater onto an aluminum foil having a thickness of 18 μm, which was a current collector, so that the amount applied was 20 mg / cm ² . Thereafter, the aluminum foil coated with the positive electrode slurry was dried at an ambient temperature of 120 ° C. for 30 minutes to obtain a positive electrode original fabric. The obtained positive electrode original fabric was pressed with a roll press so that the density was 3.8 g / cm ² to obtain a positive electrode (the thickness of the positive electrode mixture layer was 53 μm).

<Manufacture of slurry for negative electrode and negative electrode>
Artificial graphite (average particle diameter: 24.5 μm, graphite interlayer distance (interval of (002) plane (d value) by X-ray diffraction (d value)): 0.354 nm) 96 parts as negative electrode active material, and viscosity adjusting agent A 1.5% aqueous solution of carboxymethyl cellulose (manufactured by Nippon Paper Industries Co., Ltd., “MAC350”) is mixed with 1.0 part corresponding to the solid content with a disper, and ion-exchanged water is added so that the solid content concentration is 45%. , Mixed and dispersed. Next, a styrene-butadiene copolymer (manufactured by ZEON Co., Ltd., BM-400B) as a binder is further mixed with 3.0 parts corresponding to the solid content to obtain a slurry for negative electrode having a final solid content concentration of 40%. Obtained.
This negative electrode slurry was applied with a comma coater on a 18 μm-thick copper foil as a current collector so that the amount applied was 9 mg / cm ² . Thereafter, the copper foil coated with the negative electrode slurry was dried at an ambient temperature of 120 ° C. for 30 minutes to obtain a negative electrode raw material. The obtained negative electrode original fabric was pressed with a roll press so that the density was 1.6 g / cm ³ to obtain a negative electrode (the thickness of the negative electrode mixture layer was 56 μm).

<Preparation of separator>
A single-layer polypropylene separator (width 65 mm, length 500 mm, thickness 25 μm, produced by a dry method, porosity 55%) was cut into a 5 cm × 5 cm square.

<Manufacture of lithium ion secondary batteries>
An aluminum packaging exterior was prepared as the battery exterior. The positive electrode obtained above was cut into a 4 cm × 4 cm square and arranged so that the current collector-side surface was in contact with the aluminum packaging exterior. The square separator obtained above was disposed on the surface of the positive electrode mixture layer of the positive electrode. Furthermore, the negative electrode obtained above was cut into a square of 4.2 cm × 4.2 cm, and this was placed on the separator so that the surface on the negative electrode mixture layer side faces the separator. Further, a LiPF ₆ solution having a concentration of 1.0 M and containing 2.0% of vinylene carbonate was charged. The solvent of this LiPF ₆ solution is a mixed solvent (EC / EMC = 3/7 (volume ratio)) of ethylene carbonate (EC) and ethyl methyl carbonate (EMC). Furthermore, in order to seal the opening of the aluminum packaging material, heat sealing was performed at 150 ° C. to close the aluminum exterior, and a laminate type lithium ion secondary battery was manufactured. The output characteristics of the obtained lithium ion secondary battery were evaluated. The results are shown in Table 1.

(Examples 2, 11, and 12)
A conductive material dispersion, a positive electrode slurry, a negative electrode slurry, a positive electrode, a negative electrode, and a lithium ion secondary battery were used in the same manner as in Example 1 except that the following PVDF2, PVDF3, and PVDF4 were used instead of PVDF1. Manufactured. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.
PVDF2: manufactured by Arkema, KYNAR740, viscosity of 10% NMP solution: 400 mPa · s
PVDF3: manufactured by Kureha, W # 1700, viscosity of 10% NMP solution: 1750 mPa · s
PVDF4: manufactured by Kureha, W # 1300, viscosity of 10% NMP solution: 900 mPa · s

(Examples 3 to 5)
In place of EVOH1 as the ethylene-vinyl alcohol polymer, the following EVOH2, EVOH3, and EVOH4 were used, respectively, except that the conductive material dispersion, the positive electrode slurry, the negative electrode slurry, A positive electrode, a negative electrode, and a lithium ion secondary battery were manufactured. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.
EVOH2: ethylene content 44 mol%, saponification degree 96 mol%
EVOH3: ethylene content 42 mol%, saponification degree 98.5 mol%
EVOH4: ethylene content 48 mol%, saponification degree 98.5 mol%

(Examples 6 and 7)
A conductive material dispersion, a positive electrode slurry, a negative electrode slurry, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the blending amounts of EVOH1 and PVDF1 were changed as shown in Table 1. . Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 8)
A conductive material dispersion, a positive electrode slurry, a negative electrode slurry, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that NEP was used instead of NMP as the pyrrolidone solvent. . Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Examples 9, 10, and 13)
Except having changed the compounding quantity of PVDF1 like Table 1, it carried out similarly to Example 1, and manufactured the electrically conductive material dispersion liquid, the slurry for positive electrodes, the slurry for negative electrodes, the positive electrode, the negative electrode, and the lithium ion secondary battery. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 14)
Instead of carbon black α as a conductive material, carbon black β (manufactured by Denki Kagaku Kogyo Co., Ltd., Denka Black, powdered product, average particle size: 35 nm, specific surface area: 68 m ² / g, density 0.04 g / cm ³ ) A conductive material dispersion, a positive electrode slurry, a negative electrode slurry, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that ³ ) was used. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Examples 1 and 2)
A conductive material dispersion, a positive electrode slurry, a negative electrode slurry, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the amount of EVOH 1 was changed as shown in Table 1. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
When preparing the conductive material dispersion, EVOH1 (20 parts) was added in place of PVDF1 (20 parts) as the fluororesin (that is, the EVOH1 content was 28 parts). Thus, a conductive material dispersion, a positive electrode slurry, a negative electrode slurry, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

From Table 1, from Examples 1 to 14 and Comparative Examples 1 to 3, in Examples 1 to 14, a conductive material dispersion excellent in the dispersibility and storage stability of the conductive material was obtained. It turns out that the positive electrode provided with the positive electrode compound material layer obtained using a liquid can exhibit the output characteristic excellent in the lithium ion secondary battery.
Further, from Examples 1 and 3 to 5 in Table 1, by changing the saponification degree of EVOH to be used and the ethylene content, the dispersibility of the conductive material in the conductive material dispersion and the storage stability of the conductive material dispersion It can be seen that the property can be further improved.
Furthermore, from Examples 1, 2, 11, and 12 of Table 1, the viscosity of the conductive material dispersion can be further reduced by changing the viscosity of the 10 mass% NMP solution of the fluororesin used, and the conductive material It can be seen that the dispersibility of the conductive material in the dispersion and the output characteristics of the lithium ion secondary battery can be further improved.
In addition, by changing the amount of EVOH and PVDF used from Examples 1, 6, 7, 9, 10, and 13 in Table 1, the viscosity of the conductive material dispersion can be further reduced, and the conductive material It can be seen that the dispersibility of the conductive material in the dispersion and the output characteristics of the lithium ion secondary battery can be further improved.
From Examples 1 and 8 in Table 1, even when NEP is used as the pyrrolidone solvent, the viscosity of the conductive material dispersion, the dispersibility of the conductive material, the storage stability of the conductive material dispersion, and the lithium ion secondary It can be seen that the output characteristics of the battery can be made excellent.
Moreover, from Examples 1 and 14 in Table 1, the viscosity of the conductive material dispersion can be further reduced by changing the type of the conductive material, and the dispersibility of the conductive material in the conductive material dispersion, the conductive material It can be seen that the storage stability of the dispersion and the output characteristics of the lithium ion secondary battery can be further improved.

ADVANTAGE OF THE INVENTION According to this invention, the electrically conductive material can be disperse | distributed favorably and the electrically conductive element dispersion liquid for electrochemical elements which can exhibit the output characteristic excellent in the electrochemical element can be provided.
Moreover, according to this invention, the slurry for electrochemical element positive electrodes which can disperse | distribute a electrically conductive material favorably and can exhibit the output characteristic excellent in the electrochemical element can be provided.
Furthermore, according to the present invention, the positive electrode for an electrochemical element that has an electrode mixture layer in which a conductive material is well dispersed and can exhibit excellent output characteristics in an electrochemical element, and electrochemical that has excellent output characteristics An element can be provided.

Claims (9)

A conductive material, an ethylene-vinyl alcohol polymer, and a pyrrolidone solvent;
A conductive material dispersion for an electrochemical element, comprising 1 to 9 parts by mass of the ethylene-vinyl alcohol polymer per 100 parts by mass of the conductive material.   The conductive material dispersion for an electrochemical element according to claim 1, wherein the saponification degree of the ethylene-vinyl alcohol polymer is 96.0 mol% or more.   The conductive material dispersion for an electrochemical element according to claim 1 or 2, wherein the ethylene content of the ethylene-vinyl alcohol polymer is 40 mol% or more and 50 mol% or less.   Furthermore, the electrically conductive material dispersion liquid for electrochemical elements in any one of Claims 1-3 containing a fluororesin.   5. The conductive material dispersion for an electrochemical element according to claim 4, comprising 10 to 200 parts by mass of the fluororesin per 100 parts by mass of the conductive material.   6. The conductive material dispersion for an electrochemical element according to claim 4, wherein the 10 mass% N-methyl-2-pyrrolidone solution of the fluororesin has a viscosity of 10 mPa · s to 1800 mPa · s.   The slurry for electrochemical element positive electrodes containing the electrically conductive material dispersion liquid for electrochemical elements in any one of Claims 1-6, and a positive electrode active material.   A positive electrode for an electrochemical device comprising a positive electrode mixture layer prepared using the slurry for an electrochemical device positive electrode according to claim 7 on a current collector.   An electrochemical device comprising the positive electrode for an electrochemical device according to claim 8.