JP2011009116A - Binder composition for electrochemical device electrodes, slurry for electrochemical device electrodes, and electrochemical device electrode - Google Patents

Abstract

Disclosed is a binder composition for an electrochemical device electrode which can improve the diffusibility of lithium ions and can constitute an electrochemical device excellent in input / output characteristics and reliability.
A polymer particle containing (A) 20 to 40% by mass of a structural unit derived from an α, β-unsaturated nitrile compound and (B) 25 to 60% by mass of a structural unit derived from a conjugated diene compound. Is a binder composition for electrochemical device electrodes.
[Selection figure] None

Description

  The present invention relates to a binder composition for an electrochemical device electrode, a slurry for an electrochemical device electrode containing the binder composition and an electrode active material, and an electrochemical device electrode in which the slurry is applied to a current collector.

  In recent years, electronic devices have been remarkably reduced in size and weight, and accordingly, there is an extremely strong demand for downsizing and weight reduction of a battery serving as a power source. Various secondary batteries have been developed in order to satisfy such requirements. For example, nickel hydride secondary batteries and lithium ion secondary batteries have been put into practical use.

  As a method of manufacturing an electrode that is a constituent member of these secondary batteries, an active material such as a hydrogen storage alloy or graphite, carboxymethyl cellulose as a thickener, styrene-butadiene copolymer latex as a binder, dispersion There is a method of applying and drying a paste obtained by kneading water as a medium on the surface of a current collector (see, for example, Patent Documents 1 and 2).

  The binder binds the active materials and adheres the electrode layer containing the active material and the current collector. An electrochemical device including an electrode obtained by using a binder having a high binding property has properties such as good cycleability and low internal resistance. To date, secondary battery electrode binder compositions with excellent slurry stability and excellent adhesiveness with current collectors that can produce secondary batteries with low capacity loss during high-speed discharge and excellent cycle characteristics The thing (for example, refer patent document 3) is disclosed.

  In addition to adhesiveness, the binder is required to have properties such as resistance to an electrolytic solution and stability in an electrochemical environment. Conventionally, in order to satisfy these requirements, a fluororesin such as polytetrafluoroethylene or polyvinylidene fluoride dissolved in an organic solvent has been used. However, conductivity inhibition, adhesion, and chemical stability have been used. There was a problem such as. In order to solve these problems, acrylonitrile-based polymers (see, for example, Patent Document 4) and polyester-based polymers have been developed. However, none of them is sufficient to solve the above problems, and further to an electrolyte solution. Derived from problems such as elution and swelling of the battery, the battery performance such as cycle characteristics and problems in manufacturing suitability were large.

Japanese Patent Laid-Open No. 11-7948 Japanese Patent Laid-Open No. 2001-210318 JP 2009-4222 A JP 63-1212257 A

  In recent years, in order to meet the demand for higher capacity of electrochemical devices, there is a tendency to reduce the ratio of binder components contained in the material constituting the electrode layer. However, when the ratio of the binder component is reduced, there arises a problem that the adhesiveness is lowered. Therefore, a binder composition having strong adhesiveness even in a small amount has been developed. In many conventional techniques, including the above-mentioned Patent Document 3, the emphasis is mainly on the adhesion between the electrode layer and the current collector.

  The electrochemical device has a function as a secondary battery by lithium ions moving in an electrolyte and electrochemical reaction between both positive and negative electrodes. However, the problem of diffusibility of lithium ions, that is, the problem that the network structure composed of the polymer in the non-conductive binder hinders the migration of lithium ions has not been solved and still remains.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to improve lithium ion diffusibility and to provide an electrochemical device excellent in input / output characteristics and reliability. It is providing the binder composition for electrochemical device electrodes which can comprise.

  Moreover, the place made into the subject of this invention is providing the slurry for electrochemical device electrodes which can improve the diffusibility of lithium ion, and can comprise the electrochemical device excellent in the input-output characteristic and reliability.

  Another object of the present invention is to provide an electrochemical device electrode capable of improving the diffusibility of lithium ions and constituting an electrochemical device having excellent input / output characteristics and reliability.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that a structural unit derived from an α, β-unsaturated nitrile compound and a structural unit derived from a conjugated diene compound are polymer particles composed of a styrene-butadiene copolymer latex. It was found that the above-mentioned problems can be achieved by blending in a predetermined ratio, and the present invention has been completed.

  That is, according to the present invention, the following binder composition for electrochemical device electrodes, slurry for electrochemical device electrodes, and electrochemical device electrodes are provided.

[1] Polymer particles containing (A) 20 to 40% by mass of a structural unit derived from an α, β-unsaturated nitrile compound and (B) 25 to 60% by mass of a structural unit derived from a conjugated diene compound. A binder composition for an electrochemical device electrode.
[2] The binder composition for electrochemical device electrodes according to the above [1], wherein the polymer particles further contain 0.3 to 6% by mass of a structural unit derived from (C) an unsaturated carboxylic acid.
[3] The binder composition for electrochemical device electrodes according to [1] or [2], wherein the polymer particles have a number average particle diameter of 50 to 190 nm.
[4] The binder composition for an electrochemical device electrode according to any one of [1] to [3], wherein the polymer particles have a toluene gel content of 70 to 100% by mass.
[5] An electrochemical device electrode slurry comprising an electrode active material and the electrochemical device electrode binder composition according to any one of [1] to [4].
[6] An electrochemical device electrode comprising: a current collector; and an electrode layer formed by applying and drying the slurry for an electrochemical device electrode according to [5] on the surface of the current collector.

  The binder composition for an electrochemical device electrode of the present invention has an effect of improving the diffusibility of lithium ions and forming an electrochemical device excellent in input / output characteristics and reliability.

  The slurry for an electrochemical device electrode of the present invention has an effect of improving the diffusibility of lithium ions and forming an electrochemical device excellent in input / output characteristics and reliability.

  The electrochemical device electrode of the present invention has an effect of improving the diffusibility of lithium ions and forming an electrochemical device excellent in input / output characteristics and reliability.

  Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments, and based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that modifications, improvements, and the like appropriately added to the embodiments described above fall within the scope of the present invention.

1. Binder composition for electrochemical device electrodes:
The binder composition for an electrochemical device electrode of the present invention comprises (A) 20 to 40% by mass of a structural unit derived from an α, β-unsaturated nitrile compound and (B) a structural unit of 25 to 60 derived from a conjugated diene compound. The binder composition for electrochemical device electrodes containing polymer particles containing: The details will be described below.

[1] Polymer particles:
The polymer particles are composed of (A) a structural unit derived from an α, β-unsaturated nitrile compound (hereinafter also simply referred to as “(A) structural unit”) and (B) a structural unit derived from a conjugated diene compound (hereinafter referred to as “unit”). And “(B) structural unit”).

[1-1] (A) Structural unit derived from α, β-unsaturated nitrile compound:
(A) By containing a structural unit, it is estimated that a polymer particle swells moderately with electrolyte solution. That is, since the solvent enters the network structure composed of polymer chains and the network interval is widened, the solvated lithium ions can easily move through the network structure. Thereby, it is thought that the diffusibility of lithium ion improves.

  (A) Specific examples of the α, β-unsaturated nitrile compound used for constituting the structural unit include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, vinylidene cyanide and the like. Of these, acrylonitrile and methacrylonitrile are preferable, and acrylonitrile is more preferable. In addition, these (A) structural units can be used individually by 1 type or in combination of 2 or more types.

  (A) The content rate of a structural unit is 20-40 mass% in all the structural units, It is preferable that it is 20-35 mass%, and it is still more preferable that it is 20-30 mass%. (A) It is excellent in affinity with the electrolyte solution to be used as the content rate of a structural unit is 20-40 mass%, and a swelling degree does not become large too much, but it can contribute to the improvement of a battery characteristic.

[1-2] (B) Structural units derived from conjugated diene compounds:
(B) Specific examples of the conjugated diene compound used for constituting the structural unit include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, chloroprene and the like. Of these, butadiene is preferred. In addition, these (B) structural units can be used individually by 1 type or in combination of 2 or more types.

  (B) The content rate of a structural unit is 25-60 mass% in all the structural units, and it is preferable that it is 35-45 mass%. (B) When the content rate of a structural unit is 25-60 mass%, coexistence with the adhesiveness with respect to the electrical power collector of the electrode layer obtained and press tolerance is attained.

[1-3] (C) Structural unit derived from unsaturated carboxylic acid:
The polymer particles in the binder composition for an electrochemical device electrode of the present invention further contain (C) a structural unit derived from an unsaturated carboxylic acid (hereinafter also simply referred to as “(C) structural unit”). It is preferable.

  (C) Specific examples of the conjugated diene compound used to constitute the structural unit include (meth) acrylic acid and itaconic acid.

  (C) It is preferable that the content rate of a structural unit is 0.3-6 mass% in all the structural units, and it is still more preferable that it is 0.3-5 mass%. (C) When the content rate of a structural unit is 0.3-6 mass%, it is excellent in the dispersion stability of a polymer particle at the time of the slurry preparation for electrochemical device electrodes, and does not produce an aggregate easily. Further, an increase in slurry viscosity over time can be suppressed.

  Furthermore, the content ratio of the structural unit derived from itaconic acid contained in (C) the structural unit is preferably 0.15 to 3% by mass, and more preferably 0.15 to 2.5% by mass. . (C) When the content rate of the structural unit derived from itaconic acid contained in the structural unit is 0.15 to 3% by mass, the polymerization reactivity of the monomer, the molecular weight of the obtained polymer, and the like are easily controlled. As a result, polymer particles having excellent dispersion stability can be obtained, and an increase in slurry viscosity over time can be suppressed.

[1-4] Structural units derived from aromatic vinyl compounds:
The polymer particles in the binder composition for electrochemical device electrodes of the present invention preferably further contain a structural unit derived from an aromatic vinyl compound.

  Specific examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene and the like. Of these, styrene is preferred. In addition, these aromatic vinyl compounds can be used individually by 1 type or in combination of 2 or more types.

  The content ratio of the structural unit derived from the aromatic vinyl compound is preferably 10 to 60% by mass, and more preferably 20 to 55% by mass in all the structural units. When the content of the structural unit derived from the aromatic vinyl compound is 10 to 60% by mass, the polymer has an appropriate binding property to graphite used as an active material, and the obtained electrode layer is flexible. And good adhesion to the current collector.

[1-5] Structural units derived from (meth) acrylate compounds:
The polymer particles in the binder composition for electrochemical device electrodes of the present invention preferably further contain a structural unit derived from a (meth) acrylate compound. In the present specification, “(meth) acrylic acid˜” means both “acrylic acid˜” and “methacrylic acid˜”. In addition, the term “˜ (meth) acrylate” means both “˜acrylate” and “˜methacrylate”.

  Specific examples of the (meth) acrylate compound include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, and i-butyl. (Meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, 2-hexyl (meth) acrylate, octyl (meth) acrylate, i-nonyl (meth) acrylate, decyl (Meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, ethylene glycol (meth) acrylate, etc. can be mentioned. Among these, methyl (meth) acrylate, n-butyl (meth) acrylate, and i-butyl (meth) acrylate are preferable, and methyl (meth) acrylate is more preferable. In addition, these (meth) acrylate compounds can be used individually by 1 type or in combination of 2 or more types.

  It is preferable that the content rate of the structural unit derived from a (meth) acrylate compound is 5-40 mass% in all the structural units, and it is still more preferable that it is 10-30 mass%. When the content ratio of the structural unit derived from the (meth) acrylate compound is 5 to 40% by mass, the obtained polymer has an appropriate affinity with the electrolytic solution, and the binder becomes an electric resistance component in the battery. It is possible to prevent an increase in internal resistance due to, and to prevent a decrease in binding property due to excessive absorption of the electrolytic solution.

[1-6] Structural units derived from other comonomer:
The polymer particles in the binder composition for an electrochemical device electrode of the present invention are not limited to the structural units described above, but may be a monomer compound copolymerizable with these (hereinafter also simply referred to as “other copolymerizable monomers”). The derived structural unit can be contained.

  Specific examples of the other copolymer monomers include alkyl amides of ethylenically unsaturated carboxylic acids such as (meth) acrylamide and N-methylol acrylamide; vinyl carboxylic acid esters such as vinyl acetate and vinyl propionate; Examples include acid anhydrides of unsaturated dicarboxylic acids; monoalkyl esters; monoamides; aminoalkylamides of ethylenically unsaturated carboxylic acids such as aminoethylacrylamide, dimethylaminomethylmethacrylamide, and methylaminopropylmethacrylamide. In addition, these other comonomers can be used individually by 1 type or in combination of 2 or more types.

[2] Preparation of polymer particles:
The polymer particles contained in the binder composition for electrochemical device electrodes of the present invention are preferably those obtained by a two-stage emulsion polymerization process.

[2-1] First stage polymerization step:
Examples of the (I) monomer component used in the first emulsion polymerization step include α, β-unsaturated nitrile compounds, conjugated diene compounds, aromatic vinyl compounds, (meth) acrylate compounds, and other co-polymers. A non-carboxylic acid monomer such as a polymerization monomer and a carboxylic acid monomer such as an unsaturated carboxylic acid are contained. (I) The content ratio of the non-carboxylic acid monomer contained in the monomer component is 80 to 92% by mass in a total of 100% by mass of the non-carboxylic acid monomer and the carboxylic acid monomer. It is preferable that it is 82-92 mass%. When the content ratio of the non-carboxylic acid monomer is 80 to 92% by mass, the dispersion stability of the polymer particles is excellent at the time of preparing the slurry for an electrochemical device electrode, and aggregates are hardly generated. Further, an increase in slurry viscosity over time can be suppressed.

  (I) In the monomer component, the content ratio of the (meth) acrylate compound in the non-carboxylic acid monomer is preferably 14 to 30% by mass. When the content ratio of the (meth) acrylate compound is 14 to 30% by mass, the dispersion stability of the polymer particles is excellent when the slurry for the electrochemical device electrode is prepared, and aggregates are hardly generated. Further, the obtained polymer has an appropriate affinity with the electrolytic solution, and can prevent a decrease in binding property due to excessive absorption of the electrolytic solution.

  (I) In the monomer component, the content ratio of the conjugated diene compound in the non-carboxylic acid monomer is preferably 10 to 60% by mass, and the ratio of the aromatic vinyl compound is 20 to 50% by mass. It is preferable. Moreover, it is preferable that the ratio of itaconic acid in a carboxylic acid-type monomer is 50-85 mass%.

[2-2] Second stage polymerization step:
The (II) monomer component used in the second-stage emulsion polymerization process, for example, alpha, beta-unsaturated nitrile compound, a conjugated diene compound, aromatic vinyl compounds, (meth) acrylate compounds, and other co A non-carboxylic acid monomer such as a polymerization monomer and a carboxylic acid monomer such as an unsaturated carboxylic acid are contained. (II) The content ratio of the non-carboxylic acid monomer contained in the monomer component is 94 to 99% by mass in a total of 100% by mass of the non-carboxylic acid monomer and the carboxylic acid monomer. It is preferable that it is 96-98 mass%. When the content ratio of the non-carboxylic acid monomer is 94 to 99% by mass, the dispersion stability of the polymer particles is excellent at the time of preparing the slurry for an electrochemical device electrode, and aggregates are hardly generated. Further, an increase in slurry viscosity over time can be suppressed.

  (II) In the monomer, the content ratio of the (meth) acrylate compound in the non-carboxylic acid monomer is preferably 11.5% by mass or less. When the content ratio of the (meth) acrylate compound is 11.5% by mass or less, the obtained polymer has an appropriate affinity with the electrolytic solution, and the binding property is reduced due to excessive absorption of the electrolytic solution. Can be prevented.

  Further, in the polymer particle constituting monomer, the mass ratio ((I) / (II) ratio) of (I) monomer component to (II) monomer component is 0.05 to 0.5. It is preferably 0.1 to 0.4. When the (I) / (II) ratio is 0.05 to 0.5, the dispersion stability of the polymer particles is excellent during the preparation of the slurry for an electrochemical device electrode, and aggregates are hardly formed. Further, an increase in slurry viscosity over time can be suppressed.

[2-3] Emulsion polymerization:
The emulsion polymerization step is performed in an aqueous medium in the presence of an emulsifier, a polymerization initiator, and a molecular weight regulator.

[2-3-1] Emulsifier:
Specific examples of the emulsifier include an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant. In addition, these emulsifiers can be used individually by 1 type or in combination of 2 or more types.

  Specific examples of the anionic surfactant include higher alcohol sulfates, alkylbenzene sulfonates, aliphatic sulfonates, and polyethylene glycol alkyl ether sulfates.

  Specific examples of the nonionic surfactant include polyethylene glycol alkyl ester type, alkyl ether type, alkyl phenyl ether type, and the like.

  As the amphoteric surfactant, those in which the anion portion is a carboxylate, sulfate ester salt, sulfonate salt, or phosphate ester salt and the cation portion is an amine salt or a quaternary ammonium salt can be used. Specific examples of the amphoteric surfactant include betaines such as lauryl betaine and stearyl betaine; amino acid types such as lauryl-β-alanine, lauryl di (aminoethyl) glycine, and octyldi (aminoethyl) glycine.

  It is preferable that the usage-amount of an emulsifier is 0.5-5 mass parts with respect to a total of 100 mass parts of the monomer used.

[2-3-2] Polymerization initiator:
Specific examples of the polymerization initiators, sodium persulfate, potassium persulfate, water-soluble polymerization initiators such as ammonium persulfate; peroxide benzoyl, lauryl peroxide, oil-soluble, such as 2,2'-azobisisobutyronitrile Polymerization initiators: Redox polymerization initiators in combination with a reducing agent such as sodium bisulfite. These polymerization initiators can be used alone or in combination of two or more.

  It is preferable that the usage-amount of a polymerization initiator is 0.3-3 mass parts with respect to 100 mass parts of total of a monomer.

[2-3-3] Molecular weight regulator:
Specific examples of the molecular weight regulator include halogenated hydrocarbons such as chloroform and carbon tetrachloride, mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dotezyl mercaptan, and thioglycolic acid. ; dimethyl xanthogen Genji disulfide, xanthogen such as diisopropyl xanthogen Genji disulfide; terpinolene, those used in ordinary emulsion polymerization such as α- methylstyrene dimer.

  The usage-amount of a molecular weight regulator is 5 mass parts or less normally with respect to a total of 100 mass parts of monomers.

[2-4] Conditions for emulsion polymerization:
The first stage emulsion polymerization step is preferably carried out under conditions of a polymerization temperature of 40 to 80 ° C. and a polymerization time of 2 to 4 hours. In the first stage emulsion polymerization step, the polymerization conversion rate is preferably 50% or more, and more preferably 60% or more. The second emulsion polymerization step is preferably performed under conditions where the polymerization temperature is 40 to 80 ° C. and the polymerization time is 2 to 6 hours.

[3] Physical properties of polymer particles:
The number average particle diameter of the polymer particles is preferably 50 to 190 nm, and more preferably 70 to 185 nm. When the number average particle diameter is 50 to 190 nm, polymer migration does not occur in the drying step when forming the electrode, and the resulting electrode has a uniform composition. In addition, in the obtained electrode, a sufficient number of effective adhesion points can be obtained between the active material, the polymer particles, and the current collector.

  The toluene gel content of the polymer particles is preferably 70 to 100% by mass, and more preferably 75 to 100% by mass. When the toluene gel content is 70 to 100% by mass, the polymer is hardly dissolved in the electrolytic solution, and adverse effects on battery characteristics due to an increase in overvoltage can be suppressed.

  The glass transition temperature of the polymer particles is preferably -50 to 25 ° C, more preferably -30 to 5 ° C. Moreover, it is preferable that it is 15-50 mass%, and, as for the solid content concentration in the binder composition for electrochemical device electrodes of this invention, it is still more preferable that it is 20-40 mass%.

  According to such a binder composition for an electrochemical device electrode, as will be apparent from Examples described later, when the polymer is appropriately swollen in the electrolyte and mixed with the active material, the dispersibility and storage stability are improved. An electrode layer that is favorable and has high adhesion to the current collector can be formed.

2. Slurries for electrochemical device electrodes:
The slurry for electrochemical device electrodes of the present invention contains an electrode active material and the binder composition for electrochemical device electrodes.

[1] Electrode active material:
The electrode active material is not particularly limited. When used for a lithium ion secondary battery electrode, carbon can be used as the negative electrode active material. Specific examples of carbon, phenol resin, polyacrylonitrile, carbon materials obtained by baking an organic polymer compound such as cellulose, artificial graphite; carbon material obtained by calcining coke and pitch natural graphite and the like Can be mentioned. Moreover, when using for an electric double layer capacitor electrode, activated carbon, activated carbon fiber, silica, alumina, etc. can be used. In addition, when used for a lithium ion capacitor electrode, carbon materials such as graphite, non-graphitizable carbon, hard carbon, coke, polyacene organic semiconductor (PAS), and the like can be used.

[2] Additive:
The electrochemical device electrode slurry, thickener, sodium hexametaphosphate, sodium tripolyphosphate, dispersant such as sodium polyacrylate, nonionic or anionic surfactant as a stabilizer for latex, anti-foaming agents, etc. Additives can be added.

[3] Preparation of slurry for electrochemical device electrode:
The slurry for electrochemical device electrodes preferably contains 0.1 to 10 parts by mass of the binder composition for electrochemical device electrodes in terms of solid content with respect to 100 parts by mass of the electrode active material. More preferably 3 to 4 parts by mass is contained. When the content of the binder composition for an electrochemical device electrode is 0.1 to 10 parts by mass in terms of solid content, the polymer becomes difficult to dissolve in the electrolytic solution, and the adverse effect on battery characteristics due to an increase in overvoltage can be suppressed. .

  In the preparation of the slurry for the electrochemical device electrode, the stirrer, defoamer, bead mill, high-pressure homogenizer are used to mix the binder composition for the electrochemical device electrode, the electrode active material, and the additive used as necessary. Etc. can be used. Moreover, it is preferable to perform preparation of the slurry for electrochemical device electrodes under reduced pressure, and thereby it is possible to prevent bubbles from being generated in the obtained electrode layer.

3. Electrochemical device electrodes:
The electrochemical device electrode of the present invention comprises a current collector and an electrode layer formed by applying and drying the electrochemical device electrode slurry on the surface of the current collector.

[1] Current collector:
Specific examples of the current collector include metal foil, etching metal foil, and expanded metal. Specific examples of the material constituting the current collector include metal materials such as aluminum, copper, nickel, tantalum, stainless steel, and titanium, which can be appropriately selected and used depending on the type of the target electrochemical device. it can. The thickness of the current collector is preferably 5 to 30 μm and more preferably 8 to 25 μm when constituting an electrode for a lithium ion secondary battery. In the case of constituting an electrode for an electric double layer capacitor, the thickness of the current collector is preferably 5 to 100 μm, more preferably 10 to 70 μm, and particularly preferably 15 to 30 μm. .

[2] Formation of electrode layer:
Specific examples of means for applying the electrochemical device electrode slurry include a doctor blade method, a reverse roll method, a comma bar method, a gravure method, and an air knife method. Moreover, as conditions of the drying process of the coating film of the slurry for electrochemical device electrodes, it is preferable that processing temperature is 20-250 degreeC, and it is still more preferable that it is 50-150 degreeC. Moreover, it is preferable that processing time is 1-120 minutes, and it is still more preferable that it is 5-60 minutes.

Specific examples of the means for pressing include a high-pressure super press, a soft calendar, and a one-ton press. The conditions for press working are appropriately set according to the processing machine to be used. The electrode layer thus formed has a thickness of 40 to 100 μm and a density of 1.3 to 2.0 g / cm ³ . The electrochemical device electrode thus obtained can be suitably used as an electrode for electrochemical devices such as lithium ion secondary batteries, electric double layer capacitors, and lithium ion capacitors.

4). Electrochemical device:
When a lithium ion secondary battery is configured using the electrochemical device electrode of the present invention, an electrolytic solution in which an electrolyte composed of a lithium compound is dissolved in a solvent is used.

Specific examples of the _{electrolyte, LiClO 4, LiBF 4, LiI} , LiPF 6, LiCF 3 SO 3, LiAsF 6, LiSbF 6, LiAlCl 4, LiCl, LiBr, LiB (C 2 H 5) 4, LiCH 3 SO 3, _{LiC 4 F 9 SO 3, Li} (CF 3 SO 2) 2 N and the like.

  Specific examples of the solvent include carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; lactones such as γ-butyrolactone; trimethoxysilane, 1,2-dimethoxyethane, diethyl Ethers such as ether, 2-ethoxyethane, tetrahydrofuran and 2-methyltetrahydrofuran; sulfoxides such as dimethyl sulfoxide; oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane; acetonitrile, nitromethane and the like Nitrogen-containing compounds; esters such as methyl formate, methyl acetate, butyl acetate, methyl propionate, ethyl propionate, phosphoric acid triester; diglyme, triglyme, tetragrass Glymes such as acetone; ketones such as acetone, diethyl ketone, methyl ethyl ketone, and methyl isobutyl ketone; sulfones such as sulfolane; oxazolidinones such as 2-methyl-2-oxazolidinone; 1,3-propane sultone, 1,4- Examples include sultone such as butane sultone, 2,4-butane sultone, and 1,8-naphtha sultone.

  When an electric double layer capacitor is constructed using the electrochemical device electrode of the present invention, an electrolyte such as tetraethylammonium tetrafluoroborate, triethylmethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate is dissolved in the above solvent. The electrolyte solution used is used. Moreover, when comprising a lithium ion capacitor using the electrochemical device electrode of this invention, the electrolyte solution similar to the case where the said lithium ion secondary battery is comprised can be used.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified. Moreover, the measuring method of various physical-property values and the evaluation method of various characteristics are shown below.

[Number average particle size]
A light scattering measurement device (trade name “ALV5000”, manufactured by ALV) using a 22 mW He—Ne laser (λ = 632.8 nm) as a light source was used as a number average particle size measurement device.

[Toluene gel content]
2.0 g of the aqueous dispersion of the binder for an electrochemical device electrode was put into 100 g of methanol to be solidified, and filtered through a 300-mesh wire mesh to take out the aqueous dispersion. The water dispersion taken out was washed with methanol and then vacuum dried at 60 ° C. for 5 hours to obtain a dry water dispersion. The mass (W ₀ (g)) of the obtained dry water dispersion was measured, and this dry water dispersion was put into 50 ml of toluene, stirred at 50 ° C. for 3 hours, cooled to 25 ° C., and 300 mesh. Filtered through a wire mesh. 10 ml of the filtrate was collected and dried with a 120 ° C. hot plate until the mass became constant, and the mass of the dried product (W ₁ (g)) was measured. The toluene gel content (% by mass) was calculated from the following formula (1).
Toluene gel content (mass%) = {(W ₀ −5 × W ₁ ) / W ₀ } × 100 (1)

[Lithium ion secondary battery negative electrode]
(1) method for manufacturing twin-screw planetary mixer (trade name "TK high-bis mix 2P-03", manufactured by PRIMIX Co., Ltd.) to thickening agent (trade name "CMC2200", manufactured by Daicel Chemical Industries, Ltd.) 1 part (in terms of solid content) Then, 100 parts of graphite (in terms of solid content) and 68 parts of water were added as the negative electrode active material, and the mixture was stirred at 60 rpm for 1 hour. Thereafter, 1 part (in terms of solid content) of the binder composition for electrochemical device electrodes was added, and the mixture was further stirred for 1 hour to obtain a paste. The resulting aqueous was introduced into paste, after preparing the solids to 50%, stirring defoaming machine (trade name "bubble tori Rentaro", manufactured by THINKY Corporation) was used for 2 minutes at 200 rpm, at 1800rpm The slurry for an electrochemical device electrode was prepared by stirring and mixing at 1800 rpm for 1.5 minutes under a vacuum for 5 minutes. The prepared slurry for an electrochemical device electrode was uniformly applied to the surface of a current collector made of copper foil by a doctor blade method so that the film thickness after drying was 80 μm, and was dried at 120 ° C. for 20 minutes. Then, the secondary battery electrode was obtained by pressing with a roll press so that the density of an electrode layer might be 1.8 g / cm < ³ >.

(2) Peel strength A test piece having a width of 2 cm and a length of 12 cm was cut out from the secondary battery electrode, and the surface of the test piece on the electrode layer side was attached to an aluminum plate using a double-sided tape. On the other hand, a 18 mm wide tape (trade name “Cello Tape (registered trademark)”, manufactured by Nichiban Co., Ltd., JIS Z1522) was attached to the surface of the current collector of the test piece. The strength (mN / 2 cm) when this 18 mm wide tape was peeled in the 90 ° direction at a speed of 50 mm / min was measured 6 times, and the average value was calculated as the peel strength (mN / 2 cm). In addition, it can be evaluated that the larger the peel strength value, the higher the adhesion strength between the current collector and the electrode layer, and the more difficult the electrode layer peels from the current collector.

(3) Battery characteristics A negative electrode punched to a diameter of 16.16 mm was placed on a bipolar coin cell (trade name “HS Flat Cell”, manufactured by Hosen Co., Ltd.) in a glove box. Then, a separator (trade name "Celgard # 2400", manufactured by Celgard Inc.) consisting of polypropylene porous membrane punched with a diameter of 18mm with mounting a, an electrolytic solution was injected to keep out air. Thereafter, a positive electrode punched out to a diameter of 15.95 mm was placed, and the outer body of the two-pole coin cell was sealed with a screw to produce a secondary battery. The electrolytic solution used was a solution in which LiPF ₆ was dissolved at a concentration of 1 mol / liter in a solvent of ethylene carbonate / ethyl methyl carbonate = 1/1.

(3-1) Charging rate characteristics Charging over 2.5 hours by constant current (0.2 C) -constant voltage (4.2 V) method, discharging by constant current (0.2 C) method, The charge capacity at 2C was measured. Next, the battery was charged with a constant current (3C) -constant voltage (4.2V) system over 2.5 hours, discharged with a constant current (0.2C) system, and the charge capacity at 3C was measured. The ratio (%) of the charging capacity of 3C to the charging capacity at 0.2C was calculated and used as an indicator of charging rate characteristics.

(3-2) Discharge rate characteristics The battery is charged with a constant current (0.2 C) -constant voltage (4.2 V) method over 2.5 hours, discharged with a constant current (0.2 C) method, The discharge capacity at 2C was measured. Next, the battery was charged with a constant current (0.2 C) -constant voltage (4.2 V) system over 2.5 hours, discharged with a constant current (3 C) system, and the discharge capacity at 3 C was measured. The ratio (%) of the discharge capacity at 3C to the discharge capacity at 0.2C was calculated and used as an indicator of discharge rate characteristics.

(3-3) Cycle characteristics A cycle of charging with a constant current (1C) -constant voltage (4.2V) method over 2.5 hours and discharging with a constant current (1C) method is repeated. The ratio (%) of the discharge capacity at the 50th cycle to the discharge capacity was calculated and used as an indicator of cycle characteristics.

[Electric double layer capacitor electrode]
(1) method for manufacturing twin-screw planetary mixer (trade name "TK high-bis mix 2P-03", manufactured by PRIMIX Inc.), activated carbon (trade name "Kuraray call YP", manufactured by Kuraray Chemical Co., Ltd.) 100 parts, conductive carbon (trade name "Denka black", manufactured by Denki Kagaku Kogyo Co., Ltd.) 6 parts, a thickening agent (trade name "CMC2200", manufactured by Daicel chemical Industries, Ltd.), 2 parts, 278 parts of water was added, for 1 hour and stirred at 60rpm It was. Thereafter, 4 parts of a binder composition for electrochemical device electrodes was added, and further stirred for 1 hour to obtain a paste. The resulting water was poured into a paste, after the preparation of the solid content of 25%, stirring defoaming machine (trade name "bubble tori Rentaro", manufactured by THINKY Co., Ltd.) using, for 2 minutes at 200rpm, at 1800rpm The slurry for an electrochemical device electrode was prepared by stirring and mixing at 1800 rpm for 1.5 minutes under a vacuum for 5 minutes. Apply the prepared slurry for an electrochemical device electrode to the surface of a current collector made of aluminum foil uniformly by a doctor blade method so that the film thickness after drying is 150 μm, and perform a drying treatment at 120 ° C. for 20 minutes. Thus, an electric double layer capacitor electrode was obtained.

(2) Peel strength A test piece having a width of 2 cm and a length of 12 cm was cut out from the electric double layer capacitor electrode, and the aluminum foil surface of the test piece was attached to an aluminum plate using a double-sided tape. Further, a 18 mm wide tape (trade name “Cello Tape (registered trademark)” manufactured by Nichiban Co., Ltd., JIS Z1522) was attached to the surface of the test piece on the electrode layer side. The strength (mN / 2 cm) when this 18 mm wide tape was peeled in the 90 ° direction at a speed of 50 mm / min was measured 6 times, and the average value was calculated as the peel strength (mN / 2 cm).

(3) Capacitor characteristics An electric double layer capacitor electrode punched to a diameter of 16.16 mm was placed on a bipolar coin cell (trade name “HS Flat Cell”, manufactured by Hosen Co., Ltd.) in a glove box. Next, a separator (trade name “TF4535”, manufactured by Nippon Advanced Paper Co., Ltd.) punched to a diameter of 18 mm was placed, and an electrolytic solution was injected so that air did not enter. Thereafter, a similar electric double layer capacitor electrode punched out to a diameter of 15.95 mm was placed, and the outer body of the bipolar coin cell was closed with a screw and sealed to produce a capacitor. The electrolytic solution used was a solution in which (C ₂ H ₅ ) ₄ NBF ₄ was dissolved at a concentration of 1 mol / liter in a solvent of propylene carbonate.

(3-1) Capacitor capacity The capacity when charged by the constant current (10 mA / F) -constant voltage (2.7 V) system over 8 minutes and discharged by the constant current (10 mA / F) system The capacity (F / cm ² ) was used as an index.

(4) Internal resistance A value obtained by dividing the difference (ΔV) between the discharge end voltage and the initial charge voltage by the discharge current was defined as R _int and used as an index of internal resistance.

Example 1
In a temperature-controllable autoclave equipped with a stirrer, 200 parts of water, 0.6 part of sodium dodecylbenzenesulfonate, 1.0 part of potassium persulfate, 0.5 part of sodium bisulfite, α-methylstyrene dimer 2 parts, 0.1 part of dodecyl mercaptan and the first-stage polymerization component shown in Table 1 were charged all at once, and the temperature was raised to 70 ° C. to carry out the polymerization reaction for 2 hours. After confirming that the polymerization addition rate was 80% or more, the second-stage polymerization component shown in Table 1 was added over 6 hours while maintaining the reaction temperature at 70 ° C. When 3 hours passed from the start of addition of the second stage polymerization component, 0.5 part of α-methylstyrene dimer and 0.1 part of dodecyl mercaptan were added. After the addition of the second stage polymerization component, the temperature was raised to 80 ° C., and further reacted for 2 hours. After completion of the polymerization reaction, the pH of the latex was adjusted to 7.5, and 5 parts of sodium tripolyphosphate (in terms of solid content) was added. Thereafter, the residual monomer was treated with steam distillation, and concentrated under a reduced pressure to a solid content of 50% to obtain a binder composition for an electrochemical device electrode.

Using the obtained binder composition for an electrochemical device electrode, each electrode was produced by the above-described method for producing a lithium ion secondary battery negative electrode and an electric double layer capacitor electrode, and various physical properties were measured. The peel strength of the lithium ion secondary battery negative electrode was 52 mN / 2 cm, the charge rate characteristic was 90%, the discharge rate characteristic was 91%, and the cycle characteristic was 95%. The peel strength of the electric double layer capacitor electrode was 110 mN / 2 cm, the capacitor capacity was 0.9 F / cm ² , and the internal resistance was 8Ω.

(Examples 2 to 5)
Except having set it as the composition shown in Table 1, it carried out similarly to Example 1, and obtained the binder composition for electrochemical device electrodes. Using the obtained binder composition for an electrochemical device electrode, the above-described lithium ion secondary battery negative electrode and electric double layer capacitor electrode were prepared, and various physical properties were measured. The measurement results are shown in Table 1.

(Example 6)
The binder composition for an electrochemical device electrode was obtained in the same manner as in Example 1 except that the sodium dodecylbenzenesulfonate added during the polymerization of the first stage polymerization component was changed to 0.4 parts and the composition shown in Table 1 was used. It was. Using the obtained binder composition for an electrochemical device electrode, the above-described lithium ion secondary battery negative electrode and electric double layer capacitor electrode were prepared, and various physical properties were measured. The measurement results are shown in Table 1.

(Example 7)
Except having set it as the composition shown in Table 1, it carried out similarly to Example 1, and obtained the binder composition for electrochemical device electrodes. Using the obtained binder composition for an electrochemical device electrode, the above-described lithium ion secondary battery negative electrode and electric double layer capacitor electrode were prepared, and various physical properties were measured. The measurement results are shown in Table 1.

(Comparative Examples 1-4)
Except having set it as the composition shown in Table 1, it carried out similarly to Example 1, and obtained the binder composition for electrochemical device electrodes. Using the obtained binder composition for an electrochemical device electrode, the above-described lithium ion secondary battery negative electrode and electric double layer capacitor electrode were prepared, and various physical properties were measured. The measurement results are shown in Table 1.

  As shown in Table 1, the electrochemical device electrode binder compositions of Examples 1 to 7 were compared with the electrochemical device electrode compositions of Comparative Examples 1 to 4, and the current collector in the lithium ion battery The results are excellent in various properties such as adhesion to the electrode layer, charge / discharge rate characteristics, cycle characteristics, adhesion between the current collector and the electrode layer in the electric double layer capacitor, and low internal resistance. .

  Moreover, the binder composition for electrochemical device electrodes of Examples 1 to 4 in which the content ratio of the structural unit derived from the unsaturated carboxylic acid, the number average particle diameter, and the toluene gel content rate are within the predetermined ranges. Compared with the binder composition for electrochemical device electrodes of 5-7, it was the result that it was further excellent in the various characteristics in the above-mentioned lithium ion battery and an electric double layer capacitor.

  The binder composition for electrochemical device electrodes, the slurry for electrochemical device electrodes, and the electrochemical device electrode of the present invention are electrochemical devices such as secondary batteries that can be suitably used for AV equipment, OA equipment, communication equipment, etc. It is suitable as a material for constituting.

Claims (6)

(A) 20 to 40% by mass of a structural unit derived from an α, β-unsaturated nitrile compound;
(B) 25 to 60% by mass of a structural unit derived from a conjugated diene compound;
The binder composition for electrochemical device electrodes containing the polymer particle containing this.   The binder composition for an electrochemical device electrode according to claim 1, wherein the polymer particles further contain 0.3 to 6% by mass of a structural unit derived from (C) an unsaturated carboxylic acid.   The binder composition for electrochemical device electrodes according to claim 1 or 2, wherein the polymer particles have a number average particle diameter of 50 to 190 nm.   The binder composition for electrochemical device electrodes according to any one of claims 1 to 3, wherein the polymer particles have a toluene gel content of 70 to 100% by mass. An electrode active material;
The binder composition for an electrochemical device electrode according to any one of claims 1 to 4,
A slurry for an electrode of an electrochemical device containing A current collector,
An electrode layer formed by applying and drying the slurry for an electrochemical device electrode according to claim 5 on the surface of the current collector;
Electrochemical device electrode equipped with.