JP6572639B2 - Conductive material dispersion for electrochemical device, slurry for electrochemical device positive electrode, method for producing slurry for positive electrode of electrochemical device, positive electrode for electrochemical device and electrochemical device - Google Patents

Description

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

In recent years, with regard to the slurry used for forming the electrode of the electrochemical element, interest in an aqueous slurry using an aqueous solvent as a dispersion medium has been increased from the viewpoint of reducing the environmental load.
Specifically, for example, Patent Document 1 discloses a positive electrode slurry comprising a predetermined positive electrode active material, a conductive material, a water-dispersed elastomer, a water-soluble polymer, a dispersant, and water. ing. According to Patent Document 1, the positive electrode formed from this positive electrode slurry can exhibit excellent rate characteristics and cycle characteristics in a lithium ion secondary battery.

JP 2006-134777 A

  However, in the electrode slurry described in Patent Document 1, it is difficult to prepare a smooth electrode mixture layer because the conductive material and the electrode active material are easily aggregated, and the electrode mixture layer and the current collector are made strong. It was difficult to adhere. And the electrochemical element using the electrode provided with such an electrode compound-material layer had the problem that a capacity | capacitance will fall if it preserve | saves in a high temperature state. That is, the conventional electrode slurry enhances the smoothness of the electrode mixture layer while firmly adhering the electrode mixture layer and the current collector to provide battery characteristics such as high-temperature storage characteristics excellent in electrochemical devices. There was room for improvement in terms of display.

  Therefore, an object of the present invention is to provide means for advantageously solving the above-described improvements.

  The present inventor has intensively studied for the purpose of solving the above problems. Then, the present inventor first disperses and / or disperses a particulate polymer containing a nitrile group-containing monomer unit and a (meth) acrylate monomer unit, a conductive material, and a water-soluble polymer in an aqueous solvent. Dissolve to prepare a conductive material dispersion for an electrochemical device, and then mix this conductive material dispersion and an electrode active material to prepare a water-based electrode slurry. An electrode mixture layer capable of adhering to each other can be obtained, and an electrode provided with this electrode mixture layer can be found to exhibit battery characteristics such as excellent high-temperature storage characteristics for an electrochemical element, and the present invention is completed. I came to let you.

That is, this invention aims to solve the above-mentioned problem advantageously, and the conductive material dispersion for an electrochemical element of the present invention comprises a conductive material, a nitrile group-containing monomer unit and (meth) acrylic. It contains a particulate polymer containing an acid ester monomer unit, a water-soluble polymer, and water. In this way, if an electrode active material is added to a conductive material dispersion obtained by premixing a conductive material, a predetermined particulate polymer, a water-soluble polymer, and water, an electrode slurry is prepared. It is possible to form an electrode mixture layer that is excellent in properties and can be firmly adhered to a current collector, and can exhibit excellent high-temperature storage characteristics in an electrochemical element.
In the present invention, the polymer "contains a monomer unit" means "a monomer-derived structural unit is contained in a polymer obtained using the monomer". To do.
In the present invention, “(meth) acryl” means acryl and / or methacryl.
In the present invention, the term “water-soluble” means that a substance has an insoluble content of less than 0.5% by mass when 0.5 g of the substance is dissolved in 100 g of water at 25 ° C.

  Here, the conductive material dispersion for an electrochemical element of the present invention is a content ratio of the nitrile group-containing monomer unit to a content ratio of the (meth) acrylic acid ester monomer unit in the particulate polymer. The ratio is preferably from 1/20 to 1 on a mass basis. If the ratio of the content ratio of these monomer units is within the above range, the dispersibility of the conductive material and the electrode active material in the electrode slurry is improved, and the unevenness and charge concentration of the electrode mixture layer due to aggregation. It is possible to suppress deterioration due to. This is because the high-temperature storage characteristics of the electrochemical device can be further enhanced by further firmly adhering the electrode mixture layer to the current collector while further improving the smoothness of the electrode mixture layer.

  And the electrically conductive material dispersion for an electrochemical element of the present invention is the sum of the content ratio of the nitrile group-containing monomer unit and the content ratio of the (meth) acrylate monomer unit in the particulate polymer. Is preferably 50% by mass or more. When the total content of these monomer units is 50% by mass or more, both the dispersibility of the conductive material and the electrode active material in the electrode slurry and the flexibility of the obtained electrode can be improved. Because.

  In the conductive material dispersion for an electrochemical element of the present invention, the particulate polymer preferably further contains a crosslinkable monomer unit. If the particulate polymer further contains a crosslinkable monomer unit, the strength and flexibility of the resulting electrode can be improved, and the dissolution of the particulate polymer into the electrolyte solution can be suppressed, and electrochemical This is because the high-temperature storage characteristics of the device can be further enhanced.

  Here, in the conductive material dispersion for an electrochemical element of the present invention, the crosslinkable monomer unit includes an epoxy group-containing monomer unit, an N-methylolamide group-containing monomer unit, and an oxazoline group-containing single amount. It is preferably at least one selected from the group consisting of body units. The crosslinkable monomer unit is derived from at least one crosslinkable monomer selected from the group consisting of an epoxy group-containing monomer, an N-methylolamide group-containing monomer, and an oxazoline group-containing monomer. If present, the strength and flexibility of the obtained electrode can be further improved, and further the elution of the particulate polymer into the electrolyte solution can be further suppressed to further enhance the high temperature storage characteristics of the electrochemical device. Because it can.

  Furthermore, in the conductive material dispersion for an electrochemical element of the present invention, it is preferable that the particulate polymer further contains a hydrophilic group-containing monomer unit. If the particulate polymer further contains a hydrophilic group-containing monomer unit, the dispersibility of the electrode active material in the electrode slurry is improved, and the smoothness of the electrode mixture layer and the adhesion to the current collector are improved. This is because the high temperature storage characteristics of the electrochemical device can be further improved.

  Moreover, this invention aims at solving the said subject advantageously, The slurry for electrochemical element positive electrodes of this invention is a positive electrode active material, and electrically conductive material dispersion | distribution for one of the electrochemical elements mentioned above. Liquid. If the electrochemical element positive electrode slurry containing any of the above-described electrochemical element conductive material dispersions is used, a positive electrode mixture layer that is excellent in smoothness and can be firmly adhered to the current collector can be formed. The electrochemical element can exhibit excellent high-temperature storage characteristics.

  Moreover, this invention aims at solving the said subject advantageously, The manufacturing method of the slurry for electrochemical element positive electrodes of this invention is for positive electrode active materials and one of the electrochemical elements mentioned above. It includes a step of mixing the conductive material dispersion. If a positive electrode active material and any of the above-described electroconductive element conductive material dispersion liquids are mixed to prepare an electrochemical element positive electrode slurry, the positive electrode mixture is excellent in smoothness and can be firmly adhered to the current collector. A layer can be formed, and the high temperature storage characteristic excellent in the electrochemical element can be exhibited.

  Moreover, this invention aims at solving the said subject advantageously, The positive electrode for electrochemical elements of this invention is the positive mix layer prepared using the slurry for electrochemical element positive electrodes mentioned above. It is provided on a current collector. The positive electrode including the positive electrode mixture layer formed from the above-described positive electrode slurry can exhibit excellent high-temperature storage characteristics for an electrochemical element.

  Moreover, this invention aims at solving the said subject advantageously, The electrochemical element of this invention is equipped with the positive electrode for electrochemical elements mentioned above, It is characterized by the above-mentioned. An electrochemical element provided with the above-described positive electrode for an electrochemical element is excellent in battery characteristics such as high-temperature storage characteristics.

According to the present invention, it is possible to form an electrode mixture layer that is excellent in smoothness and tightly adheres to a current collector, and that is capable of exhibiting excellent high-temperature storage characteristics for an electrochemical element. A liquid can be provided.
In addition, according to the present invention, it is possible to form a positive electrode mixture layer that is excellent in smoothness and tightly adheres to a current collector, and for an electrochemical element positive electrode that can exhibit excellent high-temperature storage characteristics for an electrochemical element. A slurry and a method for producing the slurry can be provided.
Furthermore, according to this invention, the electrochemical element which can exhibit the high temperature storage characteristic excellent in the electrochemical element, and the electrochemical element excellent in high temperature storage characteristic 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 comprises the electrically conductive material dispersion liquid for electrochemical elements of this invention, and can be prepared using the manufacturing method of the slurry for electrochemical element positive electrodes 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 device of the present invention includes a particulate polymer containing a nitrile group-containing monomer unit and a (meth) acrylate monomer unit in addition to a conductive material in an aqueous solvent, and a water-soluble polymer. It is characterized by containing a functional polymer.

  According to the conductive material dispersion of the present invention, since the conductive material, the particulate polymer, and the water-soluble polymer are mixed in the aqueous solvent prior to the addition of the electrode active material, the conductive material is particulate. When the polymer and the water-soluble polymer are adsorbed appropriately and sufficiently, a conductive material that is usually easily aggregated can be well dispersed when an electrode slurry is obtained. In addition, the conductive material dispersion of the present invention contains a particulate polymer containing a nitrile group-containing monomer unit and a (meth) acrylate monomer unit. Not only the material but also the electrode active material can be well dispersed. In addition, since the particulate polymer containing both the nitrile group-containing monomer unit and the (meth) acrylic acid ester monomer unit is excellent in resistance to electrolytic solution, the elution into the electrolytic solution is small. Therefore, if the slurry for an electrochemical element electrode obtained by using the dispersion for an electrochemical element of the present invention is used, the electrode is smooth and can adhere well to the current collector in the electrolytic solution over a long period of time. Since the composite material layer can be formed, an electrochemical element having excellent high-temperature storage characteristics and the like can be obtained.

<Conductive material>
The conductive material is for ensuring electrical contact between the electrode active materials. As the conductive material, 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 type), carbon nanohorns Conductive carbon materials such as vapor-grown carbon fibers, milled carbon fibers obtained by crushing polymer fibers after firing, single layer or multilayer graphene, carbon nonwoven fabric sheets obtained by firing nonwoven fabrics made of polymer fibers, and 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.

Here, the average particle diameter 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 50 nm or less, and further preferably 40 nm or less. If the average particle diameter of the carbon black is within the above range, a good conductive path can be formed in the electrode mixture layer while ensuring the dispersibility of the carbon black as the conductive material. The smoothness and high temperature storage characteristics of the electrochemical device can be further improved.
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 30 m ² / g or more, more preferably 50 m ² / g or more, preferably 1000 m ² / g or less, more preferably 800 m ² / g or less, and even more preferably 500 m ² / g. It is as follows. If the specific surface area of the conductive material is within the above range, a good conductive path can be formed in the electrode composite layer while ensuring the dispersibility of the conductive material, and the smoothness and electrochemical properties of the electrode composite layer The high temperature storage characteristics of the 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. Moreover, a favorable conductive path can be formed in the electrode mixture layer while ensuring dispersibility, and the smoothness of the electrode mixture layer and the high-temperature storage 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.

<Particulate polymer>
The particulate polymer is produced by forming an electrode mixture layer on a current collector using an electrochemical device electrode slurry containing the conductive material dispersion of the present invention and an electrode active material. It is a water-insoluble binder that can hold the components contained in the material layer so as not to be detached from the electrode mixture layer.
The particulate polymer comprises a copolymer containing a nitrile group-containing monomer unit and a (meth) acrylate monomer unit, and optionally, a nitrile group-containing monomer unit and a (meth) acrylate ester Other monomer units other than the monomer unit may be included.
In the present invention, that a substance is “water-insoluble” means that when 0.5 g of the substance is dissolved in 100 g of water at 25 ° C., the insoluble content is 90% by mass or more.

[Nitrile group-containing monomer unit]
The nitrile group-containing monomer unit is a repeating unit derived from a nitrile group-containing monomer. Here, examples of the nitrile group-containing monomer that can form a nitrile group-containing monomer unit include an α, β-ethylenically unsaturated nitrile monomer. Specifically, the α, β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α, β-ethylenically unsaturated compound having a nitrile group. For example, acrylonitrile; α-chloroacrylonitrile, α-halogenoacrylonitrile such as α-bromoacrylonitrile; α-alkylacrylonitrile such as methacrylonitrile and α-ethylacrylonitrile; and the like. Among these, from the viewpoint of increasing the cohesive strength of the copolymer, the nitrile group-containing monomer includes acrylonitrile and methacrylonitrile (these two are collectively referred to as “(meth) acrylonitrile monomer”). Is preferred, and acrylonitrile is more preferred.
These can be used individually by 1 type or in combination of 2 or more types.

  The content ratio of the nitrile group-containing monomer unit in the particulate polymer is preferably 3% by mass or more when the total repeating unit in the particulate polymer is 100% by mass, preferably 4% by mass. % Or more, more preferably 6% by weight or more, further preferably 30% by weight or less, more preferably 27% by weight or less, and further preferably 25% by weight or less. preferable. If the content ratio of the nitrile group-containing monomer unit is within the above-mentioned range, the electrolytic resistance of the particulate polymer is increased, so that the excellent binding force of the particulate polymer in the electrolytic solution is maintained for a long period of time. As a result, the electrode mixture layer and the current collector can be more firmly adhered to each other. As a result, the high-temperature storage characteristics of the electrochemical device can be further improved.

[(Meth) acrylic acid ester monomer unit]
The (meth) acrylic acid ester monomer unit is a repeating unit derived from a (meth) acrylic acid ester monomer. Here, (meth) acrylic acid ester monomers that can form a (meth) acrylic acid ester monomer unit include (meth) acrylic acid alkyl esters and (meth) acrylic acid perfluoroalkyl esters.
As (meth) acrylic acid alkyl ester, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl Acrylic acid alkyl esters such as acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n- Butyl methacrylate, t-butyl methacrylate, isobuty Alkyl methacrylate such as methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, glycidyl methacrylate Ester; and the like.
(Meth) acrylic acid perfluoroalkyl esters include 2- (perfluorobutyl) ethyl acrylate, 2- (perfluoropentyl) ethyl acrylate, 2- (perfluorohexyl) ethyl acrylate, 2- (acrylic acid 2- ( Perfluorooctyl) ethyl, 2- (perfluorononyl) ethyl acrylate, 2- (perfluorodecyl) ethyl acrylate, 2- (perfluorododecyl) ethyl acrylate, 2- (perfluorotetradecyl) ethyl acrylate 2- (perfluoroalkyl) ethyl acrylate such as 2- (perfluorohexadecyl) ethyl acrylate; 2- (perfluorobutyl) ethyl methacrylate, 2- (perfluoropentyl) ethyl methacrylate, methacrylic acid 2 -(Perfluorohexyl) ethyl, 2- (perfluorooctyl) ethyl acrylate, 2- (perfluorononyl) ethyl methacrylate, 2- (perfluorodecyl) ethyl methacrylate, 2- (perfluorododecyl) ethyl methacrylate, 2- (perfluorometh) methacrylate Fluorotetradecyl) ethyl, 2- (perfluoroalkyl) ethyl methacrylate such as 2- (perfluorohexadecyl) ethyl methacrylate; and the like.
These can be used individually by 1 type or in combination of 2 or more types.
Here, from the viewpoint of ensuring high temperature storage characteristics of the electrochemical element while swelling the particulate polymer moderately in the electrolyte, non-carbonyl of (meth) acrylic acid alkyl ester or (meth) acrylic acid perfluoroalkyl ester The number of carbon atoms of the alkyl group or perfluoroalkyl group bonded to the reactive oxygen atom is preferably 1 or more, more preferably 3 or more, preferably 14 or less, more preferably 10 or less.

  The content ratio of the (meth) acrylic acid ester monomer unit in the particulate polymer is preferably 40% by mass or more when the total repeating unit in the particulate polymer is 100% by mass. 50% by mass or more, more preferably 65% by mass or more, preferably 97% by mass or less, more preferably 95% by mass or less, and 90% by mass or less. More preferably. If the content ratio of the (meth) acrylic acid ester monomer unit is within the above-mentioned range, the electrolytic solution resistance of the particulate polymer is increased, so that the particulate polymer has more excellent binding force in the electrolytic solution. It can be held for a long time, and the electrode mixture layer and the current collector can be more firmly adhered to each other. As a result, the high-temperature storage characteristics of the electrochemical device can be further improved.

  Here, the ratio of the content ratio of the nitrile group-containing monomer unit to the content ratio of the (meth) acrylic acid ester monomer unit in the particulate polymer is preferably 1/20 or more, more preferably on a mass basis. Is 3/17 or more, preferably 1 or less, more preferably 3/7 or less, and still more preferably 1/3 or less. If the ratio of the content ratio of the nitrile group-containing monomer unit and the (meth) acrylate monomer unit is within the above range, the dispersibility of the conductive material and the electrode active material in the electrode slurry is improved. The unevenness of the electrode mixture layer due to aggregation and the deterioration due to charge concentration can be suppressed. And the high temperature preservation | save characteristic of an electrochemical element can be further improved by making an electrode compound-material layer adhere | attach more firmly to a collector, improving the smoothness of an electrode compound-material layer more.

  The total content of the nitrile group-containing monomer units and the content of the (meth) acrylate monomer units in the particulate polymer is preferably 50% by mass or more, more preferably 60% by mass or more. More preferably, it is 65% by mass or more. If the total content of the nitrile group-containing monomer units and the content of the (meth) acrylate monomer units is 50% by mass or more, the dispersibility of the conductive material and the electrode active material in the electrode slurry In addition, both the flexibility of the obtained electrode can be improved. The upper limit of the content ratio of the nitrile group-containing monomer unit and the content ratio of the (meth) acrylate monomer unit in the particulate polymer is 100% by mass or less, preferably 95% by mass. It is as follows.

[Other monomer units]
The monomer unit other than the nitrile group-containing monomer unit and the (meth) acrylate monomer unit is not particularly limited. For example, the crosslinkable group-containing monomer unit, the hydrophilic group-containing monomer unit. , And aromatic vinyl monomer units.

-Crosslinkable monomer unit-
The crosslinkable monomer unit is a repeating unit derived from a crosslinkable monomer. Here, as the crosslinkable monomer capable of forming a crosslinkable monomer unit, the strength and flexibility of the electrode are improved, and the elution of the particulate polymer into the electrolytic solution is suppressed. From the viewpoint of further improving the high-temperature storage characteristics of the above, a monomer having a thermally crosslinkable functional group (thermal crosslinking) such as an epoxy group-containing monomer, an N-methylolamide group-containing monomer, or an oxazoline group-containing monomer Monomer).

  As an epoxy group containing monomer, the monomer containing a carbon-carbon double bond and an epoxy group is mentioned.

Examples of the monomer containing a carbon-carbon double bond and an epoxy group include unsaturated glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenyl glycidyl ether; butadiene monoepoxide, Diene or polyene monoepoxides such as chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5,9-cyclododecadiene; Alkenyl epoxides such as epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene; glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycy Rusorubeto, glycidyl linoleate, glycidyl -4
-Glycidyl esters of unsaturated carboxylic acids such as methyl-3-pentenoate, glycidyl ester of 3-cyclohexene carboxylic acid, glycidyl ester of 4-methyl-3-cyclohexene carboxylic acid, and the like.

  Examples of the N-methylolamide group-containing monomer include (meth) acrylamides having a methylol group such as N-methylol (meth) acrylamide.

  Examples of the oxazoline group-containing monomer include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, Examples include 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline.

These crosslinkable monomers can be used alone or in combination of two or more. Among these, an epoxy group-containing monomer is preferable.
The content of the crosslinkable monomer unit in the particulate polymer is preferably 0.1% by mass or more when the total repeating unit in the particulate polymer is 100% by mass. The content is preferably at most mass%, more preferably at most 5 mass%. If the content ratio of the crosslinkable monomer unit is within the above range, the strength and flexibility of the obtained electrode can be improved in a well-balanced manner, and the elution of the particulate polymer into the electrolytic solution is suppressed. Thus, the high temperature storage characteristics of the electrochemical device can be further enhanced.

-Hydrophilic group-containing monomer unit-
The hydrophilic group-containing monomer unit is a repeating unit derived from a hydrophilic group-containing monomer. Here, as the hydrophilic group-containing monomer capable of forming a hydrophilic group-containing monomer unit, a carboxylic acid-containing monomer, a hydroxyl group-containing monomer, a sulfonic acid group-containing monomer, a phosphate group Containing monomers.

Examples of the carboxylic acid group-containing monomer include monocarboxylic acids and derivatives thereof, dicarboxylic acids and acid anhydrides, and derivatives thereof.
Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid.
Examples of monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, β-diaminoacrylic acid, and the like. Can be mentioned.
Examples of the dicarboxylic acid include maleic acid, fumaric acid, itaconic acid and the like.
Dicarboxylic acid derivatives include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, methylallyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate And maleate esters such as octadecyl maleate and fluoroalkyl maleate.
Examples of the acid anhydride of dicarboxylic acid include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride.
Moreover, as a monomer which has a carboxylic acid group, the acid anhydride which produces | generates a carboxyl group by hydrolysis can also be used.
In addition, monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate Also included are monoesters and diesters of α, β-ethylenically unsaturated polyvalent carboxylic acids such as monobutyl itaconate and dibutyl itaconate.

Examples of the hydroxyl group-containing monomer include ethylenically unsaturated alcohols such as (meth) allyl alcohol, 3-buten-1-ol, and 5-hexen-1-ol; acrylic acid-2-hydroxyethyl, acrylic acid-2 -Ethylene such as hydroxypropyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, di-2-hydroxypropyl itaconate alkanol esters of unsaturated carboxylic acids; general ^{_{formula: CH 2 = CR 1 -COO- (}} C q H 2q O) p -H ( wherein, p is 2-9 integer, q is an integer from 2 to 4, esters R ¹ is a polyalkylene glycol and (meth) acrylic acid represented by hydrogen or a methyl group); 2-hydroxy-et Mono (meth) acrylic acid esters of dihydroxy esters of dicarboxylic acids such as lu-2 ′-(meth) acryloyloxyphthalate, 2-hydroxyethyl-2 ′-(meth) acryloyloxysuccinate; 2-hydroxyethyl vinyl ether; Vinyl ethers such as 2-hydroxypropyl vinyl ether; (meth) allyl-2-hydroxyethyl ether, (meth) allyl-2-hydroxypropyl ether, (meth) allyl-3-hydroxypropyl ether, (meth) allyl-2- Mono (meth) allyl ethers of alkylene glycols such as hydroxybutyl ether, (meth) allyl-3-hydroxybutyl ether, (meth) allyl-4-hydroxybutyl ether, (meth) allyl-6-hydroxyhexyl ether Polyoxyalkylene glycol mono (meth) allyl ethers such as diethylene glycol mono (meth) allyl ether and dipropylene glycol mono (meth) allyl ether; glycerin mono (meth) allyl ether, (meth) allyl-2-chloro-3 -Mono (meth) allyl ethers of halogen and hydroxy-substituted products of (poly) alkylene glycols, such as hydroxypropyl ether, (meth) allyl-2-hydroxy-3-chloropropyl ether; polyphenols such as eugenol, isoeugenol (Meth) allyl ethers of alkylene glycols such as (meth) allyl-2-hydroxyethylthioether and (meth) allyl-2-hydroxypropylthioether Ethers; and the like.
In the present invention, “(meth) allyl” means allyl and / or methallyl, and “(meth) acryloyl” means acryloyl and / or methacryloyl.

  Examples of the sulfonic acid group-containing monomer include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth) allyl sulfonic acid, styrene sulfonic acid, (meth) acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methylpropane. Examples include sulfonic acid and 3-allyloxy-2-hydroxypropane sulfonic acid.

  Examples of phosphoric acid group-containing monomers include 2- (meth) acryloyloxyethyl phosphate, methyl-2- (meth) acryloyloxyethyl phosphate, ethyl- (meth) acryloyloxyethyl phosphate, and the like.

These hydrophilic group-containing monomers can be used alone or in combination of two or more. Above all, the dispersibility of the electrode active material is improved while ensuring the dispersibility of the conductive material in the slurry for the electrode, the smoothness of the electrode mixture layer and the adhesion to the current collector, and the high temperature storage of the electrochemical element From the viewpoint of further improving the characteristics, carboxylic acid group-containing monomers, hydroxyl group-containing monomers, and sulfonic acid group-containing monomers are preferable, and carboxylic acid group-containing monomers and hydroxyl group-containing monomers are more preferable. preferable.
The content ratio of the hydrophilic group-containing monomer unit in the particulate polymer is preferably 0.1% by mass or more when all repeating units in the particulate polymer are 100% by mass. The content is more preferably 0.5% by mass or more, preferably 40% by mass or less, and more preferably 20% by mass or less. When the content ratio of the hydrophilic group-containing monomer unit is 0.1% by mass or more, the electrode active material can be favorably dispersed while ensuring the dispersibility of the conductive material in the electrode slurry. When the content is less than or equal to mass%, the dispersibility of the conductive material is not excessively impaired, and deterioration due to unevenness and charge concentration of the electrode mixture layer can be suppressed. Therefore, if the content ratio of the hydrophilic group-containing monomer unit is within the above-mentioned range, the smoothness of the electrode mixture layer and the adhesion to the current collector are further improved, and the high-temperature storage characteristics of the electrochemical device are improved. This can be further improved.

-Aromatic vinyl monomer unit-
The aromatic vinyl monomer unit is a repeating unit derived from an aromatic vinyl monomer. Here, examples of the aromatic vinyl monomer that can form an aromatic vinyl monomer unit include styrene, α-methylstyrene, vinyltoluene, and divinylbenzene. These can be used individually by 1 type or in combination of 2 or more types. Among these, styrene is preferable.

  The content ratio of the aromatic vinyl monomer unit in the particulate polymer is preferably 5% by mass or more when the total repeating unit in the particulate polymer is 100% by mass, and 8% by mass. % Or more, more preferably 40% by mass or less, and even more preferably 30% by mass or less. When the content ratio of the aromatic vinyl monomer unit is within the above range, the dispersibility of the conductive material can be further increased, and the smoothness of the electrode mixture layer can be further improved. In addition, the strength of the electrode can be ensured.

[Production method of particulate polymer]
The particulate polymer can be produced, for example, by polymerizing a monomer composition containing the above-described monomer in an aqueous solvent.
Here, in the present invention, the content ratio of each monomer in the monomer composition can be determined according to the content ratio of the monomer units (repeating units) in the particulate polymer.

The aqueous solvent is not particularly limited as long as the particulate polymer can be dispersed in a particulate state, and water may be used alone or a mixed solvent of water and another solvent may be used.
The polymerization mode is not particularly limited, and any mode such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used. As the polymerization method, any method such as ionic polymerization, radical polymerization, and living radical polymerization can be used.
And generally used emulsifiers, dispersants, polymerization initiators, polymerization aids and the like used for the polymerization can be used, and the amount used is also generally used.

The glass transition temperature of the particulate polymer obtained as described above is not particularly limited, but is preferably 15 ° C. or less, more preferably 0 ° C. or less. When the glass transition temperature of the particulate polymer is 15 ° C. or lower, sufficient flexibility can be imparted to the obtained electrode. The glass transition temperature of the particulate polymer is not particularly limited, and can be adjusted by changing the type and amount of the monomer used for forming the particulate polymer.
In addition, the glass transition temperature of a particulate polymer can be measured using the method as described in Unexamined-Japanese-Patent No. 2014-165108.

And the volume average particle diameter of a particulate polymer becomes like this. Preferably it is 0.01 micrometer or more, Preferably it is 0.5 micrometer or less, More preferably, it is 0.3 micrometer or less. If the volume average particle diameter of the particulate polymer is 0.01 μm or more, the porosity of the electrode mixture layer can be secured and battery characteristics can be secured, and if it is 0.5 μm or less, the particulate polymer The binding power is ensured.
The volume average particle diameter of the particulate polymer can be obtained as the particle diameter at which the cumulative volume calculated from the small diameter side becomes 50% in the particle diameter distribution measured by a wet method using a laser diffraction particle diameter distribution measuring apparatus. .

[Blend polymer content]
The amount of the particulate polymer in the conductive material dispersion is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and more preferably 30 parts by mass or more per 100 parts by mass of the conductive material. Is more preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and still more preferably 70 parts by mass or less. If the blending amount of the particulate polymer is 5 parts by mass or more per 100 parts by mass of the conductive material, the dispersibility of the conductive material can be secured in the conductive material dispersion, and if it is 100 parts by mass or less, the particulate form In an electrochemical element having an electrode including an electrode mixture layer formed from a conductive material dispersion, an effect of improving dispersibility commensurate with an increase in the blending amount of the polymer is obtained, and an increase in internal resistance is suppressed, The rate characteristics are not excessively degraded.

<Water-soluble polymer>
The water-soluble polymer is a component that can contribute to stabilizing the dispersion of the conductive material and the electrode active material by at least partially adsorbing on the surface of the conductive material and the electrode active material in the conductive material dispersion and the electrode slurry. In addition, the water-soluble polymer imparts viscosity to the electrode slurry, so that the coating property can be secured while suppressing the sedimentation of the components in the electrode slurry. Here, examples of the water-soluble polymer include natural polymer compounds, semi-synthetic polymer compounds, and synthetic polymer compounds. Any of these water-soluble polymers can be collected or prepared by a known method.

[Natural polymer compounds]
Examples of natural polymer compounds include plant- and animal-derived polysaccharides and proteins. Moreover, the natural high molecular compound by which the fermentation process by the microorganisms etc. and the process by a heat | fever were carried out by the case can be illustrated. These natural polymer compounds can be classified as plant natural polymer compounds, animal natural polymer compounds, microbial natural polymer compounds, and the like.

Examples of plant-based natural high molecular compounds include gum arabic, gum tragacanth, galactan, guar gum, carob gum, caraya gum, carrageenan, pectin, cannan, quince seed (malmello), arche colloid (gasso extract), starch (rice, corn, potato, Derived from wheat and the like), glycyrrhizin and the like.
Examples of the animal-based natural polymer compound include collagen, casein, albumin, gelatin and the like.
Examples of the microbial natural polymer compound include xanthan gum, dextran, succinoglucan, and bullulan.

[Semi-synthetic polymer compound]
The semi-synthetic polymer compound is obtained by modifying the above-described natural polymer compound using a chemical reaction. Such semi-synthetic polymer compounds can be classified as starch-based semi-synthetic polymer compounds, cellulose-based semi-synthetic polymer compounds, alginic acid-based semi-synthetic polymer compounds, microbial-based semi-synthetic polymer compounds, and the like.

  Examples of the starch-based semi-synthetic polymer compound include solubilized starch, carboxymethyl starch, methylhydroxypropyl starch, and modified potato starch.

Cellulose semisynthetic polymer compounds can be classified into nonionic, anionic and cationic.
Nonionic cellulose semisynthetic polymer compounds include, for example, alkylcelluloses such as methylcellulose, methylethylcellulose, ethylcellulose, and microcrystalline cellulose; hydroxyethylcellulose, hydroxybutylmethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, hydroxy And hydroxyalkylcelluloses such as propylmethylcellulose stearoxy ether, carboxymethylhydroxyethylcellulose, alkylhydroxyethylcellulose, and nonoxynylhydroxyethylcellulose;
Examples of the anionic cellulose semisynthetic polymer compound include substitution products obtained by substituting the above nonionic cellulose semisynthetic polymer compound with various derivative groups and salts thereof (sodium salt, ammonium salt, and the like). Specific examples include sodium cellulose sulfate, methyl cellulose, methyl ethyl cellulose, ethyl cellulose, carboxymethyl cellulose (CMC) and salts thereof.
Examples of the cationic cellulose semisynthetic polymer compound include low nitrogen hydroxyethyl cellulose dimethyl diallyl ammonium chloride (polyquaternium-4), O- [2-hydroxy-3- (trimethylammonio) propyl] hydroxyethyl cellulose (polyquaternium- 10), O- [2-hydroxy-3- (lauryldimethylammonio) propyl] chloride ethyl chloride (polyquaternium-24), and the like.

  Examples of the alginic acid semisynthetic polymer compound include sodium alginate and propylene glycol alginate.

  Examples of the microbial semisynthetic polymer compound include chemically modified products such as xanthan gum, dehydroxanthan gum, dextran, succinoglucan, and bullulan.

[Synthetic polymer compounds]
A synthetic polymer compound is a polymer compound that is artificially produced using a chemical reaction. Examples of such synthetic polymer compounds include poly (meth) acrylic acid polymer compounds, poly (meth) acrylate polymer compounds, polyvinyl polymer compounds, polyurethane polymer compounds, and polyether polymers. It can be classified as a compound or the like.

  Examples of the poly (meth) acrylic acid polymer compound include polyacrylic acid, polymethacrylic acid, and salts thereof.

Polyvinyl polymer compounds can be classified into nonionic, cationic and amphoteric.
Examples of nonionic polyvinyl polymer compounds include polyacrylamide, polyvinyl alcohol, polyvinyl methyl ether, polyvinyl formamide, polyvinyl acetamide, polyvinyl pyrrolidone, and the like.
Examples of the cationic polyvinyl polymer compound include dimethyldiallylammonium chloride / acrylamide (polyquaternium-7), vinylpyrrolidone / N, N-dimethylaminoethyl methacrylate copolymer diethyl sulfate (polyquaternium-11), acrylamide / β-methacryloxyethyltrimethylammonium copolymer methyl sulfate (polyquaternium-5), methylvinylimidazolinium chloride / vinylpyrrolidone copolymer ammonium salt (polyquaternium-16), vinylpyrrolidone / methacrylic acid dimethylaminopropylamide (polyquaternium) -28), vinylpyrrolidone / imidazolinium ammonium (polyquaternium-44), vinylcaprolactam / vinylpyrrolidone / methylvinylimidazolinini Mumechiru sulfate (Polyquaternium -46), N-vinylpyrrolidone / N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminoethyl methacrylate diethyl sulfate and the like.
Examples of amphoteric polyvinyl polymer compounds include acrylamide / acrylic acid / dimethyldiallylammonium chloride (polyquaternium-39), dimethyldiallylammonium chloride / acrylic acid (polyquaternium-22), dimethyldiallylammonium chloride / acrylic acid / acrylamide. A copolymer etc. are mentioned.

  Examples of polyurethane polymer compounds include anionic polyether polyurethane, cationic polyether polyurethane, nonionic polyether polyurethane, amphoteric polyether polyurethane, anionic polyester polyurethane, cationic polyester polyurethane, nonionic polyester polyurethane, and amphoteric polyester. Examples thereof include polyurethane.

  Examples of the polyether polymer compound include polyethylene glycol, polypropylene glycol, polyethylene glycol / polypropylene glycol, and the like.

  Synthetic polymer compounds include known water-soluble polymers obtained by synthesis (for example, used as amphoteric resin dispersants, resin dispersants, anionic dispersants, cationic dispersants, etc.) JP 2013-0669672 A, JP 2013-093123 A, JP 2013-206759 A, JP 2013-211161 A, and JP 2015-023015 A).

These water-soluble polymers can be used alone or in combination of two or more.
Here, in addition to the above-mentioned (i) dispersibility for dispersing the conductive material and the electrode active material, and (ii) imparting viscosity to the electrode slurry, (iii) the inside of the electrochemical element It is required to be stable at a high potential. From such a viewpoint, it is preferable to use a thickening polysaccharide as the water-soluble polymer. A thickening polysaccharide refers to a polysaccharide capable of imparting viscosity to an aqueous solvent and a compound derived from the polysaccharide. For example, some of the natural polymer compounds exemplified above and cellulose-based semi-synthetic polymer compounds Is included. Among these, from the viewpoint of enhancing the dispersibility of the conductive material and the electrode active material, a cellulose semisynthetic polymer compound is preferable, and an anionic cellulose semisynthetic polymer compound is particularly preferable.

[Properties of water-soluble polymer]
Here, the average degree of polymerization of the water-soluble polymer is preferably 500 or more, more preferably 1000 or more, preferably 2500 or less, more preferably 2000 or less, and 1500 or less. More preferably it is. If the average degree of polymerization of the water-soluble polymer is within the above range, the smoothness of the electrode mixture layer and the high-temperature storage characteristics of the electrochemical device are further improved while enhancing the dispersibility of the conductive material and the electrode active material. Can do.
In the present invention, the “average degree of polymerization of the water-soluble polymer” can be calculated from the intrinsic viscosity obtained from an Ubbelohde viscometer, and specifically can be calculated by the method described in Japanese Patent No. 5434598. .

When a cellulose semisynthetic polymer compound is used as the water-soluble polymer, the degree of etherification is preferably 0.5 or more, more preferably 0.6 or more, and 1.0 or less. It is preferable that it is 0.8 or less. If the degree of etherification of the cellulosic semisynthetic polymer compound is within the above-mentioned range, the dispersibility of the conductive material and the electrode active material is improved, and the smoothness of the electrode mixture layer and the high-temperature storage characteristics of the electrochemical device are further improved. Can be improved.
The degree of etherification of the cellulose semi-synthetic polymer compound is the average value of the number of hydroxyl groups substituted with a substituent such as a carboxymethyl group per unit of anhydrous glucose constituting the cellulose semi-synthetic polymer compound. Good, can take a value greater than 0 and less than 3. As the degree of etherification increases, the proportion of hydroxyl groups in one molecule of the cellulose-based semisynthetic polymer compound decreases (that is, the ratio of substituents increases), and as the degree of etherification decreases, the cellulose-based semisynthetic polymer compound decreases. This indicates that the ratio of hydroxyl groups in one molecule increases (that is, the ratio of substituents decreases). This degree of etherification (degree of substitution) can be determined by the method described in JP2011-34962A.

[Amount of water-soluble polymer]
The blending amount of the water-soluble polymer in the conductive material dispersion is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and 60 parts by mass or more per 100 parts by mass of the conductive material. Is more preferably 200 parts by mass or less, more preferably 160 parts by mass or less, and still more preferably 140 parts by mass or less. If the blending amount of the water-soluble polymer is 10 parts by mass or more per 100 parts by mass of the conductive material, the dispersibility of the conductive material can be secured in the conductive material dispersion, and if it is 200 parts by mass or less, the water-soluble polymer is highly soluble. In an electrochemical device having an electrode having an electrode mixture layer formed from a conductive material dispersion, an effect of improving the dispersibility commensurate with the increase in the compounding amount of the molecule is obtained, and the increase in internal resistance is suppressed. The characteristics are not excessively degraded.

<Aqueous solvent>
It does not specifically limit as an aqueous solvent contained in a electrically conductive material dispersion liquid, You may use water independently and may use the mixed solvent of water and another solvent. And the aqueous solvent contained in a electrically conductive material dispersion liquid may contain the solvent used for preparation of the particulate polymer mentioned above or a water-soluble polymer.

<Other ingredients>
In addition to the components described above, the conductive material dispersion of the present invention suppresses decomposition of the crosslinking agent, reinforcing material, antioxidant, dispersant (except for those corresponding to the above-described water-soluble polymer), and electrolyte. Components such as an electrolyte additive having a function may be mixed. As these other components, known ones can be used. Moreover, the other component may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

<Method for preparing conductive material dispersion>
When the conductive material, the particulate polymer, the water-soluble polymer, the aqueous solvent, and any other components are mixed to obtain a conductive material dispersion, there is no particular limitation on the mixing method. For example, disperse, mill, A general mixing apparatus such as a kneader can be used. The solid content concentration of the obtained conductive material dispersion is not particularly limited, but is preferably 1% by mass or more and 50% by mass or less.

(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. And if the slurry for electrochemical element positive electrodes of this invention is used, the electrode compound-material layer which is excellent in smoothness and can be firmly adhere | attached with an electrical power collector can be formed, and the high temperature storage characteristic excellent in the electrochemical element is obtained. It can be demonstrated.

  Here, the positive electrode slurry of the present invention contains a positive electrode active material, the conductive material dispersion described above, and an aqueous solvent and other components that are further added as necessary. That is, the positive electrode slurry of the present invention contains at least a positive electrode active material, a conductive material, a particulate polymer, a water-soluble polymer, and an aqueous solvent, and optionally contains other components.

<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). ), Lithium-containing composite oxide of Co—Ni—Mn, lithium-containing composite oxide of Ni—Mn—Al, lithium-containing composite oxide of Ni—Co—Al, olivine type lithium iron phosphate (LiFePO ₄ ), olivine Type lithium manganese 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.

These can be used alone or in combination of two or more. Among the above, from the viewpoint of improving battery capacity and the like in the 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. It is preferable to use lithium-containing composite oxide, Li—Ni—Co—Al lithium-containing composite oxide, Li [Ni _0.17 Li _0.2 Co _0.07 Mn _0.56 ] O ₂ or LiNi _0.5 Mn _1.5 O ₄ .
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.

<Conductive material dispersion>
As the conductive material dispersion that can be blended in the positive electrode slurry, the conductive material dispersion of the present invention containing a conductive material, a particulate polymer, a water-soluble polymer, and an aqueous solvent can be used.
In addition, the compounding quantity of a electrically conductive material dispersion liquid is not specifically limited, For example, it is set as the quantity from which a electrically conductive material will be 0.5 to 5 mass parts in conversion of solid content per 100 mass parts of positive electrode active materials. be able to.

<Other ingredients>
Other components that can be blended in the positive electrode slurry are not particularly limited, and examples thereof include the same components as the other components that can be blended in the conductive material dispersion of the present invention. Moreover, the other component may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

(Method for producing slurry for electrochemical element positive electrode)
The slurry for an electrochemical element positive electrode of the present invention described above can be prepared by mixing at least a positive electrode active material and a conductive material dispersion for an electrochemical element.
And when mixing the above-mentioned positive electrode active material, conductive material dispersion, and optionally other components and an additional aqueous solvent to obtain an electrochemical device positive electrode slurry, there is no particular limitation on the mixing method, For example, a general mixing apparatus such as a disper, a mill, or a kneader can be used.

(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 In addition, a particulate polymer and a water-soluble polymer are included. The positive electrode active material, the conductive material, the particulate polymer, and the water-soluble polymer contained in the positive electrode mixture layer are contained in the electrochemical element conductive material dispersion and the electrochemical element positive electrode slurry of the present invention. The preferred abundance ratios of the respective components are the same as the preferred abundance ratios of the respective components in the electroconductive element dispersion of the electrochemical element and the slurry for the electrochemical element positive electrode of the present invention. .

  And the positive mix layer formed from the slurry for electrochemical element positive electrodes mentioned above is excellent in smoothness, and can be firmly adhered to the current collector. Therefore, the electrochemical element having the positive electrode for an electrochemical element of the present invention having such a positive electrode mixture layer is excellent in battery characteristics such as high-temperature storage characteristics.

<Method for producing positive electrode for electrochemical device>
For the positive electrode for electrochemical devices, for example, the above-described positive electrode slurry is applied to at least one surface of the current collector (application step), and the positive electrode slurry applied to at least one surface of the current collector is dried. Thus, it is manufactured through a step (drying step) of forming a positive electrode mixture layer on the current collector. In addition, the positive electrode for electrochemical devices of the present invention can also be obtained by a method of preparing the composite particles by drying and granulating the positive electrode slurry described above, and forming a positive electrode mixture layer on the current collector using the composite particles. Can be manufactured.

[Coating process]
The method for applying the 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 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 positive electrode slurry is applied, a material having electrical conductivity and electrochemical durability is used. Specifically, as the current collector, for example, a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like can be used. Especially, as a collector used for a positive electrode, an aluminum foil is particularly preferable. In addition, the said material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

[Drying process]
The method for drying the positive electrode slurry 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, irradiation with infrared rays, electron beam, or the like. A drying method is mentioned. By drying the positive electrode slurry on the current collector in this way, a positive electrode mixture layer is formed on the current collector, and a positive electrode for an electrochemical device comprising the current collector and the positive electrode mixture layer can be obtained. it can.

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 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 battery characteristics such as high-temperature storage 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.

<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. Of these, 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 is not specifically limited, For example, the thing of Unexamined-Japanese-Patent No. 2012-204303 can be used. Among these, the thickness of the separator as a whole 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 addition, in a polymer produced by copolymerizing a plurality of types of monomers, the proportion of monomer units formed by polymerizing a certain monomer in the polymer is usually unless otherwise specified. This coincides with the ratio (preparation ratio) of the certain monomer in the total monomers used for polymerization of the polymer.
In Examples and Comparative Examples, the smoothness of the positive electrode mixture layer, the adhesion strength retention rate of the positive electrode mixture layer after high temperature storage, and the high temperature storage characteristics of the electrochemical device were evaluated using the following methods, respectively.

<Smoothness>
The produced positive electrode was cut out to 3 cm × 3 cm to form a test piece, and this test piece was set on a laser microscope with the current collector side facing down. Then, using a 50 × lens, the arithmetic average roughness Ra value of any five locations of the positive electrode mixture layer was measured in accordance with JIS B0601: 2001 (ISO 4287: 1997) in the range of 100 μm × 100 μm. . This was performed for 10 test pieces, and an average value (average Ra value) of all measured values (5 locations × 10 sheets) was calculated. And it converted into the index value (Ra relative value) which made 100 average Ra value of Example 1, and evaluated by the following references | standards. It shows that a positive electrode compound material layer is excellent in smoothness, so that this value is small.
A: Ra relative value is 100 or less B: Ra relative value is more than 100 and less than 200 C: Ra relative value is more than 200 and less than 500 D: Ra relative value is more than 500 <Adhesion strength maintenance ratio after high temperature storage>
The produced positive electrode was cut into a rectangle having a width of 1 cm and a length of 10 cm to obtain a test piece, and fixed with the surface on the positive electrode mixture layer side facing up. After applying a cellophane tape (as defined in JIS Z1522) to the surface of the test piece on the positive electrode mixture layer side, the cellophane tape was peeled off from one end of the test piece in a 180 ° direction at a speed of 50 mm / min. When the stress was measured. The measurement was performed 10 times, the average value was obtained, and this was used as the initial peel strength P0.
In addition to the above operation, the prepared lithium ion secondary battery was charged to a cell voltage of 4.2 V by a constant current method of 0.5 C in a 25 ° C. atmosphere and stored for 3 weeks in a 60 ° C. atmosphere (high temperature storage). )did. The cell was disassembled after storage at high temperature, and the taken-out positive electrode was washed with an electrolyte solvent (a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC / EMC = 3/7 (volume ratio))). , Dried. Next, a test piece was cut out into a rectangle having a width of 1 cm and a length of 10 cm, and the peel strength P1 after high-temperature storage was determined in the same manner as the initial peel strength P0.
Then, adhesion strength maintenance ratio (%) = (peel strength P1 / peel strength P0) × 100 was determined and evaluated according to the following criteria. As the adhesion strength maintenance rate is larger, the positive electrode mixture layer can sufficiently maintain the adhesion state with the current collector under high temperature storage, and the positive electrode mixture layer and the current collector are more firmly adhered.
A: Adhesion strength maintenance rate is 80% or more B: Adhesion strength maintenance rate is 70% or more and less than 80% C: Adhesion strength maintenance rate is 60% or more and less than 70% D: Adhesion strength maintenance rate is 50% or more and less than 60% E : Adhesion strength maintenance rate is less than 50% <high temperature storage characteristics>
The manufactured lithium ion secondary battery was charged to a cell voltage of 4.2 V by a constant current method of 0.5 C in an atmosphere at 25 ° C. and then discharged to 3.0 V, and an initial discharge capacity C0 was measured. Next, the lithium ion secondary battery was charged to a cell voltage of 4.2 V by a constant current method of 0.5 C in a 25 ° C. atmosphere. Thereafter, the lithium ion secondary battery was stored for 3 weeks (high temperature storage) in an atmosphere of 60 ° C. After storage at high temperature, it was discharged to 3 V by a constant current method of 0.5 C, and the remaining capacity C1 after storage at high temperature was measured.
Then, capacity retention ratio (%) = (remaining capacity C1 / initial discharge capacity C0) × 100 was obtained and evaluated according to the following criteria. It shows that a lithium ion secondary battery is excellent in a high temperature storage characteristic, so that a capacity | capacitance maintenance factor is large.
A: Capacity maintenance ratio is 90% or more B: Capacity maintenance ratio is 85% or more and less than 90% C: Capacity maintenance ratio is 80% or more and less than 85% D: Capacity maintenance ratio is 75% or more and less than 80% E: Capacity maintenance ratio Is less than 75%

Example 1
<Preparation of particulate polymer>
To a reactor equipped with a stirrer, 70 parts of ion-exchanged water, 0.2 part of sodium dodecylbenzenesulfonate as an emulsifier and 0.3 part of potassium persulfate as a polymerization initiator were respectively supplied. The temperature was raised to 60 ° C. On the other hand, in a separate container, 50 parts of ion-exchanged water, 0.5 part of sodium dodecylbenzenesulfonate as an emulsifier, 15 parts of acrylonitrile as a nitrile group-containing monomer, n-butyl as a (meth) acrylic acid ester monomer 30 parts of acrylate and 42 parts of ethyl acrylate, 2.0 parts of glycidyl methacrylate as a crosslinkable monomer, 1.0 part of methacrylic acid as a hydrophilic group-containing monomer, 10 parts of styrene as an aromatic vinyl monomer Were mixed to obtain a monomer mixture. This monomer mixture was continuously added to the reactor over 4 hours for polymerization. The reaction was carried out at 60 ° C. during the addition of the monomer mixture. After the addition of the monomer mixture was completed, the reaction was further completed by stirring at 70 ° C. for 3 hours. The polymerization conversion rate was 99.5% or more. The obtained polymerization reaction liquid is cooled to 25 ° C., aqueous ammonia is added to adjust the pH to 7, and then steam is introduced to remove unreacted monomers to disperse the particulate polymer in water. A liquid (solid content concentration: 40%) was obtained. The volume average particle diameter of the particulate polymer was 0.2 μm.
<Preparation of conductive material dispersion>
100 parts of acetylene black (specific surface area 68 m ² / g, average particle size 35 nm, density: 0.04 g / cm ³ ) as a conductive material, 50 parts of an aqueous dispersion of the above-mentioned particulate polymer in a solid content equivalent, water-soluble After mixing 100 parts of an aqueous solution of sodium salt of carboxymethyl cellulose (average polymerization degree 1000 to 1200, etherification degree 0.65 to 0.75) as a solid polymer in an amount corresponding to the solid content, an appropriate amount of water is added and a bead mill is added. To obtain a conductive material dispersion. The obtained conductive material dispersion had a solid content concentration of 15% by mass.
<Preparation of slurry for positive electrode>
100 parts of active material LiCoO ₂ (volume average particle diameter: 10 μm) having a layered structure as a positive electrode active material and an appropriate amount of water are added to the conductive material dispersion (2 parts of conductive material) obtained as described above. The mixture was stirred with a disper (3000 rpm, 60 minutes) to prepare a positive electrode slurry. The solid content concentration of the obtained positive electrode slurry was 50% by mass.
<Manufacture of positive electrode>
An aluminum foil with a thickness of 20 μm was prepared as a current collector. The slurry for positive electrode obtained as described above was applied on an aluminum foil with a comma coater so that the basis weight after drying was 20 mg / cm ² , dried at 60 ° C. for 20 minutes, and 120 ° C. for 20 minutes, A positive electrode raw material was obtained by heat treatment at 60 ° C. for 10 hours. This positive electrode original fabric was rolled by a roll press to produce a positive electrode comprising a positive electrode mixture layer having a density of 3.2 g / cm ³ and an aluminum foil. The positive electrode had a thickness of 70 μm. Using the obtained positive electrode, the smoothness was evaluated. The results are shown in Table 1.
<Preparation of slurry for negative electrode>
In a planetary mixer with a disper, 100 parts of artificial graphite (volume average particle size: 24.5 μm) having a specific surface area of 4 m ² / g as a negative electrode active material, and a 1% aqueous solution of carboxymethyl cellulose as a dispersant (Daiichi Kogyo Seiyaku Co., Ltd.) 1 part of “BSH-12” manufactured by the company was added in an amount corresponding to the solid content, adjusted to a solid content concentration of 55% with ion-exchanged water, and mixed at 25 ° C. for 60 minutes. Next, the solid content concentration was adjusted to 52% with ion-exchanged water. Thereafter, the mixture was further mixed at 25 ° C. for 15 minutes to obtain a mixed solution.
Into the mixed liquid obtained as described above, 1.0 part of a 40% aqueous dispersion of a styrene-butadiene copolymer (with a glass transition temperature of −15 ° C.) in an amount corresponding to a solid content, and ion-exchanged water are added. The final solid content concentration was adjusted to 50%, and the mixture was further mixed for 10 minutes. This was defoamed under reduced pressure to obtain a negative electrode slurry having good fluidity.
<Manufacture of negative electrode>
The slurry for the negative electrode was applied on a copper foil having a thickness of 20 μm, which is a current collector, with a comma coater so that the film thickness after drying was about 150 μm and dried. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Then, the negative electrode original fabric was obtained by heat-processing at 120 degreeC for 2 minute (s). This negative electrode original fabric was rolled with a roll press to obtain a negative electrode having a negative electrode mixture layer with a thickness of 80 μm.
<Preparation of separator>
A single-layer polypropylene separator (width 65 mm, length 500 mm, thickness 25 μm, manufactured 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. Further, 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, vinylene carbonate (VC) containing 1.5%, was charged with LiPF ₆ solution having a concentration of 1.0 M. 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 at 150 ° C. was performed to close the aluminum exterior, and a lithium ion secondary battery was manufactured. High temperature storage characteristics were evaluated using the obtained lithium ion secondary battery. In addition, the adhesion strength maintenance rate after high temperature storage was evaluated using this lithium ion secondary battery and the positive electrode described above. The results are shown in Table 1.

(Examples 2 to 5)
A particulate polymer was prepared in the same manner as in Example 1 except that the monomers shown in Table 1 were used in the proportions shown in the table. A conductive material dispersion, a positive 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 each of these particulate polymers was used, and various evaluations were performed. The results are shown in Table 1.

(Comparative Examples 1-2)
As the particulate polymer, polybutyl acrylate (prepared in the same manner as the particulate polymer of Example 1 except that only butyl acrylate was used as a monomer), polyvinylidene fluoride (“KF” manufactured by Kureha Co., Ltd.) Except for using Polymer # 7200 "), a conductive material dispersion, a positive electrode slurry, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced in the same manner as in Example 1, and various evaluations were performed. The results are shown in Table 1.

In Table 1 below,
“AcB” indicates acetylene black,
“AN” stands for acrylonitrile,
“BA” represents n-butyl acrylate,
“EA” indicates ethyl acrylate,
“GMA” indicates glycidyl methacrylate,
“AGE” represents allyl glycidyl ether;
“MAA” indicates methacrylic acid,
“ST” indicates styrene,
“PBA” indicates polybutyl acrylate,
“PVDF” indicates polyvinylidene fluoride,
“CMC-Na” represents a sodium salt of carboxymethyl cellulose.

From Table 1, implementation using a conductive material, a particulate polymer containing a nitrile group-containing monomer unit and a (meth) acrylate monomer unit, a water-soluble polymer, and a conductive material dispersion containing water In Examples 1 to 5, it can be seen that an electrode mixture layer that is smooth and firmly adhered to the current collector can be formed, and as a result, a lithium ion secondary battery having excellent high-temperature storage characteristics can be obtained.
Further, from Table 1, in Comparative Examples 1 and 2 using a conductive material dispersion using a particulate polymer not containing at least one of a nitrile group-containing monomer unit and a (meth) acrylate monomer unit. It can be seen that the smoothness of the electrode mixture layer and the adhesion to the current collector cannot be ensured, and the high-temperature storage characteristics of the resulting lithium ion secondary battery deteriorate.

According to the present invention, it is possible to form an electrode mixture layer that is excellent in smoothness and tightly adheres to a current collector, and that is capable of exhibiting excellent high-temperature storage characteristics for an electrochemical element. A liquid can be provided.
In addition, according to the present invention, it is possible to form a positive electrode mixture layer that is excellent in smoothness and tightly adheres to a current collector, and for an electrochemical element positive electrode that can exhibit excellent high-temperature storage characteristics for an electrochemical element. A slurry and a method for producing the slurry can be provided.
Furthermore, according to this invention, the electrochemical element which can exhibit the high temperature storage characteristic excellent in the electrochemical element, and the electrochemical element excellent in high temperature storage characteristic can be provided.

Claims (10)

Conductive material, particulate polymer containing a nitrile group-containing monomer units and (meth) acrylic acid ester monomer units, containing a water-soluble polymer, and water, a for an electrochemical device conducting material dispersion ,
A conductive material dispersion for an electrochemical element, wherein a blending amount of the water-soluble polymer is 60 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the conductive material.   The ratio of the content ratio of the nitrile group-containing monomer unit to the content ratio of the (meth) acrylic acid ester monomer unit in the particulate polymer is 1/20 or more and 1 or less on a mass basis. The electroconductive element dispersion for an electrochemical element according to claim 1.   The total of the content rate of the said nitrile group containing monomer unit in the said particulate polymer and the content rate of the said (meth) acrylic acid ester monomer unit is 50 mass% or more. Conductive material dispersion for electrochemical devices.   The conductive material dispersion for an electrochemical element according to claim 1, wherein the particulate polymer further contains a crosslinkable monomer unit.   The crosslinkable monomer unit is at least one selected from the group consisting of an epoxy group-containing monomer unit, an N-methylolamide group-containing monomer unit, and an oxazoline group-containing monomer unit. 5. A conductive material dispersion for an electrochemical element according to 4.   The conductive material dispersion for an electrochemical element according to claim 1, wherein the particulate polymer further contains a hydrophilic group-containing monomer unit.   The slurry for electrochemical element positive electrodes containing the positive electrode active material and the electrically conductive material dispersion liquid for electrochemical elements in any one of Claims 1-6.   The manufacturing method of the slurry for electrochemical element positive electrodes including the process of mixing the positive electrode active material and the electrically conductive material dispersion liquid for electrochemical elements in any one of Claims 1-6.   A positive electrode for an electrochemical element, comprising a positive electrode mixture layer prepared using the slurry for an electrochemical element positive electrode according to claim 7 on a current collector.   An electrochemical device comprising the positive electrode for an electrochemical device according to claim 9.