JP5163919B1 - Electrode binder composition - Google Patents

Abstract

The present invention is an electrode binder composition comprising polymer particles and a liquid medium, wherein at least a part of the polymer particles contain fluorine atoms, and dynamic light scattering is performed on the polymer particles. It is related with the said binder composition for electrodes characterized by the particle size frequency distribution measured by the method being multimodal.
The binder composition for electrodes provides an electrode excellent in all of ionic conductivity, oxidation resistance (charge / discharge characteristics) and adhesion.
[Selection] Figure 1

Description

The present invention relates to an electrode binder composition.
The binder composition of the present invention contains polymer particles having a specific particle size distribution, is excellent in all of ionic conductivity, oxidation resistance and adhesion, and is used as a binder material for electrodes of power storage devices, particularly for positive electrodes. Is preferred.

In recent years, a power storage device having a high voltage and a high energy density is required as a power source for driving electronic equipment. Lithium ion batteries, lithium ion capacitors, and the like are expected as power storage devices that can meet this demand.
The electrode used for such an electricity storage device is usually produced by applying and drying a mixture of active material particles and polymer particles functioning as an electrode binder onto the surface of the current collector. The properties required for the polymer particles used in the electrode include the ability to bind active material particles, the ability to bind the active material particles to the current collector, the abrasion resistance in the process of winding the electrode, and subsequent cutting. As a result, there can be mentioned powder-off resistance in which fine powder of the active material is not generated from the applied electrode composition layer (hereinafter also simply referred to as “active material layer”). When the polymer particles satisfy these various required characteristics, the degree of freedom in designing the structure of the electricity storage device, such as the method of folding the obtained electrode and setting the winding radius, is increased, and the miniaturization of the device is achieved. Can do. In addition, it has been empirically clarified that the quality of the active material particles is substantially proportional to the ability to bind the active material particles, the binding ability between the active material particles and the current collector, and the powder-off resistance. . Therefore, in the present specification, hereinafter, the term “adhesiveness” may be used in a comprehensive manner.
As an electrode binder (especially a binder used for manufacturing a positive electrode), it is advantageous to use an organic polymer containing a fluorine atom having excellent ionic conductivity and oxidation resistance, such as polyvinylidene fluoride (PVDF). However, organic polymers containing fluorine atoms generally have poor adhesion, and thus have a problem with the mechanical strength and durability of the resulting electrode. Therefore, various techniques for improving the adhesion while maintaining the ionic conductivity and oxidation resistance of the organic polymer have been studied and proposed.
For example, Patent Document 1 proposes a technique for achieving both the lithium ion conductivity and oxidation resistance of the negative electrode binder and adhesion by using PVDF and a rubbery polymer in combination. Patent Document 2 discloses a technique for improving adhesion by applying a solution obtained by dissolving PVDF in a specific organic solvent on the surface of a current collector and then removing the solvent at a low temperature. Has been proposed. Further, Patent Document 3 proposes a technique for improving adhesion by applying an electrode binder having a structure in which a main chain composed of a vinylidene fluoride copolymer has a side chain containing a fluorine atom.

JP 2011-3529 A JP 2010-55847 A JP 2002-42819 A

However, according to the technique of Patent Document 1 in which an organic polymer containing a fluorine atom and a rubbery polymer are used in combination, although the adhesion is improved, the ionic conductivity of the organic polymer is reduced and the oxidation resistance is improved. It is greatly damaged. Therefore, the electrical storage device manufactured using this has the problem that charging / discharging characteristics will deteriorate irreversibly by repetition of charging / discharging. Further, according to the techniques of Patent Documents 2 and 3 that use only an organic polymer containing a fluorine atom as an electrode binder, the level of adhesion is still insufficient.
Thus, in the prior art, there is no known electrode binder material that provides an electrode that is excellent in both ionic conductivity, oxidation resistance, and adhesion.
This invention is made | formed in view of such a present condition, The objective provides the binder material for electrodes which gives the electrode which is excellent in all of ionic conductivity, oxidation resistance (charge / discharge characteristic), and adhesiveness. There is.

The above objects and advantages of the present invention are as follows:
A binder composition for an electrode containing polymer particles and a liquid medium ,
Ri particle diameter frequency distribution is bimodal der measured by dynamic light scattering method for the previous SL polymer particles, and
The polymer belonging to at least one of two peaks in the particle size frequency distribution of the polymer particles,
A polymer A having a repeating unit derived from at least one selected from the group consisting of vinylidene fluoride, ethylene tetrafluoride and propylene hexafluoride;
A polymer B having a repeating unit derived from an unsaturated carboxylic acid ester;
Characterized Oh Rukoto a polymer alloy particles consisting, are achieved by the electrode binder composition.

By using the binder composition for an electrode of the present invention, it is possible to produce an electrode having excellent ionic conductivity and oxidation resistance and having high adhesion.
An electricity storage device including an electrode manufactured using the binder composition for an electrode of the present invention has extremely good charge / discharge rate characteristics, which is one of electrical characteristics.

3 is a particle size frequency distribution chart of polymer particles obtained in Example 2. FIG. 6 is a particle size frequency distribution chart of polymer particles obtained in Comparative Example 3.

Hereinafter, preferred embodiments of the present invention will be described in detail.
It should be understood that the present invention is not limited to only the embodiments described below, and includes various modified examples that are implemented without departing from the scope of the present invention.
1 Electrode Binder Composition The electrode binder composition of the present invention contains polymer particles and a liquid medium as described above. In addition to these, the electrode binder composition may contain other components such as an emulsifier, a polymerization initiator or a residue thereof, a surfactant, and a neutralizing agent.

1.1 Polymer Particles The polymer particles contained in the electrode binder composition of the present invention are :
Measured by dynamic light scattering method was particle diameter frequency distribution are two bimodal der, and
The polymer belonging to at least one of the two peaks in the particle size frequency distribution of the polymer particles contains a fluorine atom .
The content ratio of fluorine atoms to the entire polymer particles is preferably 2 to 30% by mass, more preferably 3 to 28% by mass, and particularly preferably 5 to 25% by mass. By making the content rate of a fluorine atom into said range, it can be set as the polymer particle excellent in the balance of oxidation resistance and adhesiveness, and is preferable.
The content ratio of the fluorine atom can be measured by, for example, combustion ion chromatography.
The polymer particles are measured particle diameter frequency distribution is bimodal by dynamic light scattering method.
Here, the "particle size distribution is bimodal" particle size and (r) on the horizontal axis, in the particle diameter frequency distribution curve taken occurrence frequency of (f) on the vertical axis, the peak of the frequency of occurrence That there are multiple. In other words, when considering a graph in which the particle size (r) is plotted on the horizontal axis and the appearance frequency (f) is differentiated by the particle size (r) (df / dr) on the vertical axis, (df / dr) value, with increasing particle size (r), increases starting from 0, and then decreased to negative and become once through the 0, then the particle diameter frequency repeating 2 cycles back to 0 turned to increase again Distribution. At this time, the particle diameter (r) when the (df / dr) value starts from 0, increases, and then decreases to 0 is set as the maximum frequency diameter of the peak .

Of the two peaks that make up the particle size distribution of the polymer particles,
1 Peak is peaks having the maximum frequency diameter in the range (first size range) of 40 to 100 nm,
Another peak is preferably peaked der Rukoto having the maximum frequency diameter in the range (second size range) of 200 to 500 nm. The first particle size range is more preferably 45 to 75 nm. The second particle size range is more preferably 300 to 490 nm, and particularly preferably 400 to 480 nm. The particle size polymer particles produced by using the electrode binder composition containing electrodes cloth adhesion (binding between the active material having a peak of such two size ranges thereto respectively 1 peak Both adhesion and adhesion between the active material layer and the current collector are particularly excellent. The reason for this is not yet clear, but the smaller polymer particles belonging to the first particle size range fill the gaps in the structure generally bound by the large polymer particles belonging to the second particle size range, It is estimated that strong adhesion can be obtained. Furthermore, by setting the particle size of the polymer particles in the above range, the internal resistance of the active material layer can be kept low while obtaining strong adhesion. This is a truly surprising effect. Therefore, it is preferable that the polymer particles in the present invention exhibit a particle size frequency distribution that does not have a peak having the maximum frequency diameter other than the above two particle size ranges.
Proportion shown the area _{(S 1)} with respect to the total of the peaks of the area belonging to the first peaks of the area belonging to a particle size range _{(S 1)} and the second particle size range _{(S 2) (S 1 /} ( S ₁ + S ₂ )) is preferably 0.1 to 0.9, more preferably 0.2 to 0.8, and particularly preferably 0.4 to 0.6.
The particle diameter frequency distribution of the polymer particles in the first size range and a second size range, each having a one-peak, and have a crest having the highest frequency diameters in the range other than those Ru bimodal der otherwise. By using polymer particles having such a particle size frequency distribution, the effect of the present invention, which is a balance between low resistance and adhesiveness, can be expressed to the maximum, which is preferable.
The particle size frequency distribution of the polymer particles can be measured by a commercially available particle size frequency distribution measuring apparatus based on a dynamic light scattering method. Examples of commercially available products of such a particle size frequency distribution measuring apparatus include model “MT3300” and “NPA150” manufactured by Nikkiso Co., Ltd.

The polymer particles having the particle size frequency distribution as described above can be, for example, a mixture of a plurality of types of polymer particles having a single particle size frequency distribution measured by a dynamic light scattering method. This mixture can be easily obtained by preferably mixing a plurality of polymer latexes produced by emulsion polymerization under different conditions at a predetermined ratio. When polymer particles having a bimodal particle size frequency distribution are produced by this method, the maximum frequency diameter (D ₂ ) of the peaks belonging to the second particle size range and the maximum of the peaks belonging to the first particle size range. The ratio (D ₂ / D ₁ ) to the frequency diameter (D ₁ ) is preferably a value exceeding 2, more preferably 2.5 or more, further preferably 3 or more, particularly 5 The above is preferable. By mixing two kinds of polymer particles in such a particle size range, polymer particles exhibiting a clear bimodal particle size frequency distribution can be obtained. Is preferable in that it is surely expressed.
Preferred conditions for emulsion polymerization will be described later.

The polymer particles in the present invention are polymer particles belonging to at least one of two peaks in the particle size frequency distribution.
Vinylidene fluoride, Ru Oh a fluorine atom-containing polymer particles containing a polymer having a repeating unit derived from at least one selected from the group consisting of tetrafluoroethylene and hexafluoropropylene. In the particle size frequency distribution of the polymer particles, the polymer particles belonging to peaks other than the peak to which the fluorine atom-containing polymer particles belong may be the same fluorine atom-containing polymer particles as described above, or The polymer particle which does not contain may be sufficient.
Most preferably,
The particle size distribution of the polymer particles is bimodal, and each of the polymer particles belonging to both peaks is at least selected from the group consisting of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. In the case of fluorine atom-containing polymer particles containing a polymer having a repeating unit derived from one type, or
The particle size frequency distribution of the polymer particles is bimodal, and the polymer particles belonging to one of the peaks are at least one selected from the group consisting of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene This is a case where the polymer particle is a fluorine atom-containing polymer particle containing a polymer having a repeating unit derived therefrom, and the polymer particle belonging to the other peak is a polymer particle containing no fluorine atom.

1.1.1 Fluorine atom-containing polymer particles The fluorine atom-containing polymer particles are composed of a repeating unit derived from one or more of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, vinylidene fluoride, to have the repeating units derived from one or more copolymerizable other unsaturated monomers of tetrafluoroethylene and hexafluoropropylene.
Examples of such other unsaturated monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, and (meth) acrylic. N-butyl acid, i-butyl (meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylic 2-ethylhexyl acid, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, ethylene (meth) acrylate Glycol, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, tri (meth) Trimethylolpropane crylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, allyl (meth) acrylate, ethylene di (meth) acrylate, etc. (Meth) acrylic acid ester of
Aromatic vinyl compounds such as styrene, α-methylstyrene, divinylbenzene;
Vinyl esters of carboxylic acids such as vinyl acetate and vinyl propionate;
Halogenated olefins such as vinyl fluoride, vinyl chloride, vinylidene chloride;
Conjugated dienes such as butadiene, isoprene, chloroprene;
Α-olefins such as ethylene and propylene;
α, β-unsaturated nitrile compounds;
Unsaturated carboxylic acids;
Alkyl amides of unsaturated carboxylic acids;
Unsaturated dicarboxylic acid anhydrides;
Monoalkyl esters of unsaturated dicarboxylic acids;
Monoamides of unsaturated dicarboxylic acids;
Examples thereof include aminoalkylamides of unsaturated carboxylic acids, and one or more selected from these can be used.

In the present specification, “(meth) acrylic acid” is a concept encompassing both “acrylic acid” and “methacrylic acid”.
The content of the repeating unit derived from at least one selected from vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene in the fluorine atom-containing polymer particles is preferably 1 with respect to the total mass of the polymer particles. It is more than mass%, More preferably, it is 3-70 mass%, More preferably, it is 5-60 mass%.
The content ratio of the repeating unit derived from vinylidene fluoride in the fluorine atom-containing polymer particles is preferably 1 to 70% by mass, and more preferably 3 to 50% by mass. The content ratio of the repeating unit derived from tetrafluoroethylene in the fluorine atom-containing polymer particles is preferably 20% by mass or less, more preferably 1 to 10% by mass, and further preferably 2 to 5% by mass. is there. The content ratio of the repeating unit derived from hexafluoropropylene in the fluorine atom-containing polymer particles is preferably 30% by mass or less, more preferably 1 to 20% by mass, and further preferably 2 to 10% by mass. is there.
Such fluorine atom-containing polymer particles include at least one unsaturated monomer selected from the above-mentioned vinylidene fluoride, ethylene tetrafluoride and propylene hexafluoride, and optionally other unsaturated monomers. Can be easily produced by emulsion polymerization according to a known method.
The fluorine atom-containing copolymer particles are
Off Kka vinylidene, and the polymer A having a repeating unit derived from at least one selected from the group consisting of tetrafluoroethylene and hexafluoropropylene,
Ru Oh a polymer alloy particles containing a polymer B having a repeating unit derived from an unsaturated carboxylic acid ester. It is preferable to use polymer alloy particles as the fluorine atom-containing copolymer particles because the resistance of the obtained electrode is reduced and oxidation resistance and adhesion can be expressed simultaneously.

1.1.1.1 Polymer Alloy Particles “Polymer alloy” is, according to the definition in “Iwanami Physical and Chemical Dictionary 5th edition. Iwanami Shoten”, “a mixture of two or more polymers or chemical bonds. "A generic term for component polymers", "a polymer blend in which different types of polymers are physically mixed, a block and graft copolymer in which different types of polymer components are bonded by covalent bonds, and different types of polymers that are associated by intermolecular forces. A polymer complex, an IPN (Interpenetrating Polymer Network) in which different types of polymers are entangled with each other. However, the polymer alloy particles contained in the electrode binder composition of the present invention are referred to as IPN (interpenetrating polymer network) among “polymer alloys in which different types of polymer components are not bonded by covalent bonds”. It is what is done .
The polymer A constituting the polymer alloy particle is excellent in ionic conductivity, and the hard segment of the crystalline resin is aggregated to give the main chain a pseudo-crosslinking point such as C—H—F—C. it is conceivable that. For this reason, when the polymer A is used alone as the binder resin, its ionic conductivity and oxidation resistance are good, but the adhesion and flexibility are insufficient, and therefore the adhesion is low. On the other hand, the polymer B constituting the polymer alloy particles is excellent in adhesion and flexibility, but has low oxidation resistance. Therefore, when the polymer B is used alone as an electrode (particularly positive electrode) as a binder resin, Good charge / discharge characteristics cannot be obtained because of repeated oxidative decomposition due to repeated discharge.

However, by using polymer alloy particles containing the polymer A and the polymer B, an ionic conductivity, oxidation resistance, and adhesion can be expressed simultaneously, and an electrode having good charge / discharge characteristics is obtained. It became possible to manufacture. When the polymer alloy particles are composed only of the polymer A and the polymer B, the oxidation resistance can be further improved, which is preferable.
When the polymer alloy particles are measured by differential scanning calorimetry (DSC) based on JIS K7121, it is preferable that the polymer alloy particles have only one endothermic peak in the temperature range of −50 to 250 ° C. The temperature of this endothermic peak is more preferably in the range of -30 to + 30 ° C.
When the polymer A constituting the polymer alloy particles is present alone, it generally has an endothermic peak (melting temperature) at −50 to 250 ° C. In addition, the polymer B constituting the polymer alloy particles generally has an endothermic peak (glass transition temperature) different from that of the polymer A. For this reason, when the polymer A and the polymer B in the particles are present in phase separation as in, for example, a core-shell structure, two endothermic peaks should be observed at −50 to 250 ° C. However, when there is only one endothermic peak at −50 to 250 ° C., it can be estimated that the particles are polymer alloy particles.
Furthermore, when the temperature of only one endothermic peak of the polymer alloy particles is in the range of −30 to + 30 ° C., the particles can impart better flexibility and tackiness to the active material layer. Therefore, the adhesiveness can be further improved, which is preferable.

1.1.1.2 Polymer A
The polymer alloy particles preferably contained in the electrode binder composition of the present invention are polymers A having a repeating unit derived from at least one selected from the group consisting of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene. contains.
The content ratio of the repeating unit derived from at least one selected from vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene in the polymer A is preferably 80% by mass with respect to the total mass of the polymer A. It is above, More preferably, it is 90 mass% or more.
The content ratio of the repeating unit derived from vinylidene fluoride in the polymer A is preferably 50 to 99% by mass and more preferably 80 to 98% by mass with respect to the total mass of the polymer A. The content ratio of the repeating unit derived from tetrafluoroethylene in the polymer A is preferably 50% by mass or less, more preferably 1 to 30% by mass, and further preferably 2 to 20% by mass. (A) The content ratio of the repeating unit derived from hexafluoropropylene in the polymer particles is preferably 50% by mass or less, more preferably 1 to 30% by mass, and further preferably 2 to 25% by mass. is there.
The polymer A preferably has only a repeating unit derived from at least one selected from the group consisting of vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene.

1.1.1.3 Polymer B
The polymer alloy particles preferably contained in the electrode binder composition of the present invention contain a polymer B having a repeating unit derived from an unsaturated carboxylic acid ester. In general, a component such as polymer B has good adhesion, but is considered to have poor ionic conductivity and oxidation resistance, and has not been used for positive electrodes. However, in the present invention, by using such a polymer B as a polymer alloy particle together with the polymer A, it has succeeded in developing sufficient ionic conductivity and oxidation resistance while maintaining good adhesion. It is a thing.
The unsaturated carboxylic acid ester that leads the repeating unit constituting the polymer B is preferably a (meth) acrylic acid ester.

1.1.1.3.1 (Meth) acrylic acid ester Specific examples of such (meth) acrylic acid ester include alkyl esters of (meth) acrylic acid, cycloalkyl esters of (meth) acrylic acid, Examples thereof include alkenyl esters of (meth) acrylic acid, hydroxyalkyl esters of (meth) acrylic acid, (poly) (meth) acrylic esters of polyhydric alcohols, and the like. Specific examples of these include alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and i-propyl (meth) acrylate. , N-butyl (meth) acrylate, i-butyl (meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, (meth) acrylic acid 2 -Ethylhexyl, n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, etc .;
Examples of the cycloalkyl ester of (meth) acrylic acid include cyclohexyl (meth) acrylate and the like;
Examples of the alkenyl ester of (meth) acrylic acid include allyl (meth) acrylate and ethylene di (meth) acrylate;
Examples of the hydroxyalkyl ester of (meth) acrylic acid include hydroxymethyl (meth) acrylate and hydroxyethyl (meth) acrylate;
Examples of the (poly) (meth) acrylic acid ester of the polyhydric alcohol include, for example, ethylene glycol (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, tri (meth) acrylate tri Examples include methylolpropane, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, and dipentaerythritol hexa (meth) acrylate, and one or more selected from these. Can be. Of these, alkyl esters of (meth) acrylic acid are preferable, and one or more selected from methyl (meth) acrylate, ethyl (meth) acrylate, and 2-ethylhexyl acrylate are more preferable. Particularly preferred is methyl (meth) acrylate.
The polymer B may be a polymer having only a repeating unit derived from an unsaturated carboxylic acid ester, and in addition to the repeating unit derived from an unsaturated carboxylic acid ester, another unsaturated monomer capable of copolymerization. You may have the structural unit derived from a body.
The content ratio of the repeating unit derived from the unsaturated carboxylic acid ester in the polymer B is preferably 65% by mass or more, more preferably 75% by mass or more with respect to the total mass of the polymer B.
Examples of the other unsaturated monomers include α, β-unsaturated nitrile compounds, unsaturated carboxylic acids, conjugated diene compounds, aromatic vinyl compounds, and other unsaturated monomers.

1.1.1.3.2 Structural unit derived from α, β-unsaturated nitrile compound Polymer B has a repeating unit derived from an α, β-unsaturated nitrile compound, so that an electrolytic solution of polymer alloy particles Can be further improved. That is, the presence of the nitrile group makes it easier for the solvent (medium) to enter the network structure composed of polymer chains and the network interval is widened, so that the solvated lithium ions can easily move through the network structure. Thereby, it is thought that the diffusibility of lithium ion improves, As a result, electrode resistance falls and it can implement | achieve more favorable charging / discharging characteristics.
Specific examples of the α, β-unsaturated nitrile compound include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, vinylidene cyanide, and the like. Can be. Among these, at least one selected from acrylonitrile and methacrylonitrile is preferable, and acrylonitrile is particularly preferable.
The content ratio of the structural unit derived from the α, β-unsaturated nitrile compound is preferably 35% by mass or less, and more preferably 10 to 25% by mass in all the structural units.

1.1.1.3.3 Constituent Unit Derived from Unsaturated Carboxylic Acid When polymer B has a structural unit derived from an unsaturated carboxylic acid, the stability of the binder composition for an electrode of the present invention is improved. .
Specific examples of the unsaturated carboxylic acid include mono- or dicarboxylic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. It can be more than a seed. In particular, at least one selected from acrylic acid, methacrylic acid and itaconic acid is preferable.
The content ratio of the repeating unit derived from the unsaturated carboxylic acid is preferably 15% by mass or less, more preferably 0.3 to 10% by mass in all the structural units.

1.11.3.4 Constituent Unit Derived from Conjugated Diene Compound Binder composition for an electrode that provides a strong electrode having excellent viscoelastic properties when polymer B has a structural unit derived from a conjugated diene compound It becomes easy to manufacture a thing. That is, when a polymer having a structural unit derived from a conjugated diene compound is used, it becomes a polymer alloy particle having a cross-linked structure while having a low Tg, so that it easily functions as a binder having a balance between elongation and strength. As a result, the adhesion can be further improved.
Examples of the conjugated diene compound include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene and the like. , One or more selected from these. As the conjugated diene compound, 1,3-butadiene is particularly preferable.
The content ratio of the structural unit derived from the conjugated diene compound is preferably 35% by mass or less and more preferably 25% by mass or less in all the structural units.

1.1.1.3.5 Constituent Unit Derived from Aromatic Vinyl Compound When polymer B has a constituent unit derived from an aromatic vinyl compound, it is prepared using the binder composition for an electrode of the present invention. When the slurry for electrodes contains a conductivity-imparting agent, the affinity for this can be made better.
Specific examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, and the like, and one or more selected from these can be used. be able to. Among the above, the aromatic vinyl compound is particularly preferably styrene.
The content ratio of the structural unit derived from the aromatic vinyl compound is preferably 35% by mass or less, and more preferably 25% by mass or less in all the structural units.

1.1.1.3.6 Constituent units derived from other comonomer The specific examples of other comonomer that leads to the constituent unit of the polymer B include (meth) acrylamide, N -Alkylamides of ethylenically unsaturated carboxylic acids such as methylolacrylamide;
Carboxylic acid vinyl esters such as vinyl acetate and vinyl propionate;
Unsaturated dicarboxylic acid anhydrides;
Monoalkyl esters of unsaturated dicarboxylic acids;
Monoamides of unsaturated dicarboxylic acids;
Examples thereof include aminoalkylamides of unsaturated carboxylic acids such as aminoethylacrylamide, dimethylaminomethylmethacrylamide, and methylaminopropylmethacrylamide, and one or more selected from these.

1.1.1.4 Synthesis of Polymer Alloy Particles As long as the polymer alloy particles preferably contained in the electrode binder composition of the present invention have the above-described configuration, the synthesis method is not particularly limited. For example, it can be easily synthesized by a known emulsion polymerization process or by appropriately combining these processes.
For example, first, a polymer A having a repeating unit derived from at least one selected from the group consisting of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene is synthesized by a known method, and then the polymer A is synthesized. The monomer for constituting the polymer B is added, and the monomer is sufficiently absorbed into the stitch structure of the polymer particles made of the polymer A. The polymer alloy particles can be easily produced by a method of synthesizing the polymer B by polymerizing the absorbed monomer. When polymer alloy particles are produced by such a method, it is essential for the polymer A to sufficiently absorb the monomer of the polymer B. When the absorption temperature is too low or the absorption time is too short, only a part of the core-shell particle or the surface layer becomes a particle having an IPN type structure, and the polymer alloy particle in the present invention cannot be obtained in many cases. However, if the absorption temperature is too high, the pressure of the polymerization system becomes too high, which is disadvantageous in terms of reaction system handling and reaction control, and even if the absorption time is excessively long, further advantageous results are not obtained. .
From the above viewpoint, the absorption temperature is preferably 30 to 100 ° C, more preferably 40 to 80 ° C;
The absorption time is preferably 1 to 12 hours, and more preferably 2 to 8 hours. At this time, it is preferable to lengthen the absorption time when the absorption temperature is low, and a short absorption time is sufficient when the absorption temperature is high. The conditions are such that the value obtained by multiplying the absorption temperature (° C.) and the absorption time (h) is generally in the range of 120 to 300 (° C. · h), preferably 150 to 250 (° C. · h).
The operation of absorbing the monomer of the polymer B in the stitch structure of the polymer A is preferably performed in a known medium used for emulsion polymerization, for example, in water.
The content of the polymer A in the polymer alloy particles is preferably 3 to 60% by mass, more preferably 5 to 55% by mass, and more preferably 10 to 50% by mass in 100% by mass of the polymer alloy particles. More preferably, it is particularly preferably 20 to 40% by mass. When the polymer alloy particles contain the polymer A in the above range, the balance between the ionic conductivity and the oxidation resistance and the adhesion becomes better.

1.1.1.5 Conditions for Emulsion Polymerization Polymerization for producing preferred fluorine atom-containing polymer particles in the present invention, that is , polymerization of polymer A and polymerization of polymer B in the presence of polymer A , Respectively, in the presence of a known polymerization initiator, molecular weight regulator, emulsifier (surfactant), and the like.
Examples of the polymerization initiator include water-soluble polymerization initiators such as sodium persulfate, potassium persulfate, and ammonium persulfate;
Oil-soluble polymerization initiators such as benzoyl peroxide, lauryl peroxide, 2,2′-azobisisobutyronitrile;
A redox type polymerization initiator by a combination of any of the above polymerization initiators and a reducing agent such as sodium bisulfite can be mentioned. These polymerization initiators can be used singly or in combination of two or more.
The proportion of the polymerization initiator used is the sum of the monomers used (in the production of polymer A, the sum of monomers leading to polymer A, in the case of polymerizing polymer B in the presence of polymer A). The total of the monomers that lead to the polymer B. The same applies hereinafter.) It is preferably 0.3 to 3 parts by mass with respect to 100 parts by mass.
Examples of the molecular weight regulator include halogenated hydrocarbons such as chloroform and carbon tetrachloride;
mercaptan compounds such as n-hexyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dotezyl mercaptan, thioglycolic acid;
Xanthogen compounds such as dimethylxanthogen disulfide and diisopropylxanthogen disulfide;
Other molecular weight regulators such as terpinolene and α-methylstyrene dimer can be mentioned. These molecular weight regulators can be used singly or in combination of two or more.
The use ratio of the molecular weight regulator is preferably 5 parts by mass or less with respect to 100 parts by mass in total of the monomers used.

Examples of the emulsifier include an anionic surfactant, a nonionic surfactant, an amphoteric surfactant, and a fluorine-based surfactant.
Examples of the anionic surfactant include higher alcohol sulfates, alkylbenzene sulfonates, aliphatic sulfonates, polyethylene glycol alkyl ether sulfates;
Examples of the nonionic surfactant include polyethylene glycol alkyl esters, polyethylene glycol alkyl ethers, polyethylene glycol alkyl phenyl ethers, and the like.
Examples of amphoteric surfactants include those in which the anion moiety is composed of a carboxylate, sulfate ester, sulfonate or phosphate ester salt, and the cation moiety is composed of an amine salt, a quaternary ammonium salt, or the like. Can be mentioned. Specific examples of such amphoteric surfactants include betaine compounds such as lauryl betaine and stearyl betaine;
Examples thereof include surfactants of amino acid type such as lauryl-β-alanine, lauryl di (aminoethyl) glycine, octyldi (aminoethyl) glycine.
Examples of the fluorosurfactant include fluorobutyl sulfonate, phosphoric acid ester having a fluoroalkyl group, a salt of a carboxylic acid having a fluoroalkyl group, and a fluoroalkylethylene oxide adduct. Examples of such commercially available fluorosurfactants include F-top EF301, EF303, and EF352 (manufactured by Mitsubishi Materials Electronics Chemical Co., Ltd.);
Megafuck F171, F172, F173 (manufactured by DIC Corporation);
Fluorard FC430, FC431 (manufactured by Sumitomo 3M);
Asahi Guard AG710, Surflon S-381, S-382, SC101, SC102, SC103, SC104, SC105, SC106, Surfinol E1004, KH-10, KH-20, KH-30, KH-40 (Asahi Glass Co., Ltd.) );
Examples of the solvent include 250, 251, 222F and FTX-218 (manufactured by Neos Co., Ltd.).

As an emulsifier, the 1 type (s) or 2 or more types selected from the above can be used.
The use ratio of the emulsifier is preferably 0.01 to 10 parts by mass, and more preferably 0.02 to 5 parts by mass with respect to 100 parts by mass in total of the monomers used.
The emulsion polymerization is preferably carried out in a suitable aqueous medium, particularly preferably in water. The total content of the monomers in the aqueous medium can be 10 to 50% by mass, and preferably 20 to 40% by mass.
The conditions for emulsion polymerization are preferably a polymerization time of 2 to 24 hours at a polymerization temperature of 40 to 85 ° C, and more preferably a polymerization time of 3 to 20 hours at a polymerization temperature of 50 to 80 ° C.

1.1.2 Polymer Particles Not Containing Fluorine Atoms The polymer particles not containing a fluorine atom are preferably (meth) acrylic acid esters, aromatic vinyl compounds, vinyl esters of carboxylic acids, halogenated olefins, conjugated dienes. And polymer particles having repeating units derived from at least one unsaturated monomer selected from the group consisting of α-olefins, more preferably (meth) acrylic acid esters, aromatic vinyl compounds and conjugated dienes Polymer particles having repeating units derived from at least one unsaturated monomer selected from the group consisting of: Specific examples of these unsaturated monomers are the same as those exemplified for the other unsaturated monomers that the fluorine atom-containing polymer particles can optionally have.
The polymer particles containing no fluorine atom can be easily produced by emulsion polymerization of the unsaturated monomer as described above or a mixture thereof according to a known method. Specifically, the emulsion polymerization can be performed in the same manner as described in 1.1.1.5 above.

1.1.3 Method for Controlling Particle Size Range of Polymer Particles The above-mentioned fluorine atom-containing polymer particles and polymer particles not containing fluorine atoms are each changed in particle size by appropriately changing the conditions for emulsion polymerization. The range can be different. Specifically, the particle size range of the polymer particles obtained can be easily controlled by appropriately setting the use ratio of the emulsifier in the emulsion polymerization. If the use ratio of the emulsifier is decreased, the particle size of the obtained polymer tends to increase, and if the use ratio of the emulsifier is increased, the particle diameter of the obtained polymer tends to decrease.
When the polymerization conversion rate of the monomer used is significantly large, the polymerization time does not significantly affect the particle size of the resulting polymer.
When the polymer particles are polymer alloy particles, the number of polymer particles obtained is determined in advance depending on the number of polymer A serving as a seed. Therefore, when polymer B is polymerized in the presence of polymer A, The use ratio of the emulsifier hardly affects the particle diameter of the polymer alloy particles. In the case of polymer alloy particles, attention should be paid to the proportion of emulsifier used in the production of the polymer A.
The use ratio of the emulsifier for controlling the particle size range of the polymer particles used in the present invention is as follows for each specific embodiment of the polymer particles.
One-step polymerization of polymer particles having a repeating unit derived from at least one selected from the group consisting of vinylidene fluoride, ethylene tetrafluoride and propylene hexafluoride as at least a part of the polymer particles in the present invention When synthesizing with
The use ratio of the emulsifier for obtaining the polymer particles having the maximum frequency diameter in the first particle size range may be 0.5 to 5 parts by mass with respect to 100 parts by mass in total of the monomers used. Preferably;
The use ratio of the emulsifier for obtaining polymer particles having the maximum frequency diameter in the second particle size range is 0.02 to 0.5 parts by mass with respect to 100 parts by mass in total of the monomers used. It is preferable.
When the polymer alloy particles are used as at least a part of the polymer particles, the use ratio of the emulsifier in producing the polymer A greatly affects the particle size of the obtained polymer alloy particles as described above. . The use ratio of the emulsifier in producing the polymer A is as follows:
The use ratio of the emulsifier for obtaining the polymer alloy particles having the maximum frequency diameter in the first particle size range is preferably 1 to 10 parts by mass with respect to 100 parts by mass in total of the monomers used;
The use ratio of the emulsifier for obtaining the polymer alloy particles having the maximum frequency diameter in the second particle size range may be 0.05 to 1 part by mass with respect to 100 parts by mass in total of the monomers used. preferable. In this case, a polymer A having a maximum frequency diameter of about 0.3 to 0.7, preferably about 0.4 to 0.6 is obtained with respect to the maximum frequency diameter of the desired polymer alloy particles. .

When using polymer particles that do not contain fluorine atoms as at least a part of the polymer particles in the present invention,
The proportion of the emulsifier used to obtain the polymer having the maximum frequency diameter in the first particle size range is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass in total of the monomers used. ;
The use ratio of the emulsifier for obtaining the polymer having the maximum frequency diameter in the second particle size range is 0.005 to 0.2 part by mass with respect to 100 parts by mass in total of the monomers used. Is preferred.
Since the optimum use ratio of the emulsifier varies slightly depending on the type of emulsifier used, the polymerization conditions, etc., a general optimum numerical range cannot be clearly presented. Therefore, the recommended use ratio of the emulsifier for obtaining the polymer having the maximum frequency diameter in the first particle size range described above and the emulsifier for obtaining the polymer having the maximum frequency diameter in the second particle size range. The recommended usage ratio has an apparently overlapping portion. However, the appropriate proportion of emulsifier can be easily set by a few preliminary experiments by those skilled in the art.
As described above, a plurality of polymer particles having different particle size ranges or a plurality of latexes each containing polymer particles having different particle size ranges can be obtained. Combined particles or their latex can be obtained.

1.2 Liquid medium The electrode binder composition of the present invention further contains a liquid medium.
The liquid medium is preferably an aqueous medium containing water. This aqueous medium can contain a small amount of non-aqueous medium in addition to water. Examples of such a non-aqueous medium include amide compounds, hydrocarbons, alcohols, ketones, esters, amine compounds, lactones, sulfoxides, sulfone compounds, and the like, and one or more selected from these are used. can do. The content ratio of such a non-aqueous medium is preferably 10% by mass or less, more preferably 5% by mass or less, based on the entire aqueous medium. Most preferably, the aqueous medium is composed only of water without containing a non-aqueous medium.
The binder composition for electrodes of the present invention uses an aqueous medium as a medium, and preferably does not contain a non-aqueous medium other than water. This is preferable because the degree of adverse effects on the environment is low and the safety for handling workers is high. In this regard, a composition containing an organic solvent as a medium causes problems of disposal and cost, and requires fireproof storage equipment due to characteristics such as flammability, and has special skills and considerations in handling. There is a disadvantage that is necessary.

1.3 Electrode Binder Composition The electrode binder composition of the present invention preferably exists as a latex in which the polymer particles as described above are dispersed in the liquid medium as described above.
As the binder composition for an electrode of the present invention, polymer particles are synthesized (polymerized), preferably after mixing a plurality of polymerization reaction mixtures after stopping the reaction, and adjusting the liquidity of the mixture as necessary. This is preferably used as it is as the binder composition for an electrode of the present invention. Therefore, the electrode binder composition of the present invention may contain other components such as an emulsifier, a polymerization initiator or its residue, a surfactant, and a neutralizer in addition to the polymer particles as described above. . As a content ratio of these other components, the total mass of the other components is preferably 3% by mass or less, more preferably 2% by mass or less, as a ratio with respect to the mass of the solid content of the composition.
The solid content concentration of the binder composition for an electrode of the present invention (ratio of the mass of components other than the aqueous medium in the composition to the total mass of the composition) is preferably 30 to 50% by mass. It is more preferable that it is 35-45 mass%.
The liquid property of the electrode binder composition is preferably near neutral, more preferably pH 6.0 to 8.5, and particularly preferably pH 7.0 to 8.0. For adjusting the liquidity of the composition, a known water-soluble acid or base can be used. Examples of the acid include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid and the like;
Examples of the base include sodium hydroxide, potassium hydroxide, lithium hydroxide, and aqueous ammonia.
The binder composition for electrodes of the present invention as described above can be suitably used as an electrode material for power storage devices such as lithium ion secondary batteries, electric double layer capacitors, and lithium ion capacitors. Since the advantageous effect of this invention is exhibited to the maximum when the binder composition for electrodes is used as a material for the positive electrode of a lithium ion secondary battery, it is particularly preferable to apply to this application.

2 Electrode slurry As described above, an electrode slurry can be produced using the electrode binder composition of the present invention.
The electrode slurry is a dispersion used to form an active material layer on the current collector after being applied to the surface of the current collector and then dried. This electrode slurry contains at least the polymer particles as described above, an active material, and water, and preferably further contains a conductivity-imparting material. In addition to these, a non-aqueous medium, a thickener and the like may be contained.

2.1 Active Material The active material is appropriately selected according to the type of the target power storage device.
For electrode slurry for forming a positive electrode of a lithium ion secondary battery (slurry for the positive electrode), as the active material (positive electrode active material), for example, _{Li 1 + x M y N z} O 2 ( where, M is Co, Ni And at least one selected from Mn, N is at least one selected from Al and Sn, O represents an oxygen atom, and x, y, and z are 0.10 ≧ x ≧ 0, 4.00, respectively. ≧ y ≧ 0.85, 2.00 ≧ z ≧ 0 in the range)), composite metal oxide, lithium cobaltate, lithium nickelate, lithium manganate, lithium iron phosphate, ternary system In addition to nickel cobalt lithium manganate,
A lithium atom-containing oxide having an olivine structure can be preferably used.
The lithium atom-containing oxide having the olivine structure has the following general formula (1):
Li _1-x M _x (XO ₄ ) (1)
(In the formula (1), M is a metal ion selected from the group consisting of Mg, Ti, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Zn, A1, Ga, Ge, and Sn. At least one of;
X is at least one selected from the group consisting of Si, S, P and V;
x is a number and satisfies the relationship 0 <x <1. )
And a compound having an olivine type crystal structure. X in the above formula (1) is selected according to the valences of M and X so that the valence of the entire formula (1) becomes zero.
The lithium atom-containing oxide having the olivine structure has different electrode potentials depending on the type of the metal element M. Therefore, the battery voltage can be arbitrarily set by selecting the type of the metal element M. Typical examples of the lithium atom-containing oxide having an olivine structure include LiFePO ₄ , LiCoPO ₄ , Li _0.90 Ti _0.05 Nb _0.05 Fe _0.30 Co _0.30 Mn _0.30 PO _{4, and the} like. Can be mentioned. Among these, LiFePO ₄ is particularly preferable because it is easy to obtain an iron compound as a raw material and is inexpensive. In addition, a compound obtained by substituting Fe ions in the above compounds with Co ions, Ni ions, or Mn ions has the same crystal structure as each of the above compounds, and thus has the same effect as a positive electrode active material.

In the case of the slurry for electrodes (slurry for negative electrodes) for forming the negative electrode of a lithium ion secondary battery, as an active material (negative electrode active material), a carbon material, carbon, etc. can be used suitably, for example. Examples of the carbon material include carbon materials obtained by firing organic polymer compounds, coke, pitch, and the like. Examples of the organic polymer compounds that are precursors of the carbon materials include phenol resins and polyacrylonitrile. And cellulose. Examples of the carbon include artificial graphite and natural graphite.
In the case of an electrode slurry for forming an electrode for an electric double layer capacitor, examples of the active material include graphite, non-graphitizable carbon, and hard carbon;
Carbon material obtained by firing coke, pitch, etc .;
A polyacene organic semiconductor (PAS) or the like can be used.
The active material is preferably in the form of particles, and the average particle diameter (Db) is preferably in the range of 0.4 to 10 μm, and more preferably in the range of 0.5 to 7 μm.

2.2 Water The electrode slurry may further contain water. By containing water, the stability of the electrode slurry is improved, and the electrode can be produced with good reproducibility. Water has a higher evaporation rate than a high boiling point solvent (for example, N-methylpyrrolidone, etc.) generally used in electrode slurries (especially positive electrode slurries), and productivity is reduced by shortening the solvent removal time. Improvement, suppression of particle migration, etc. can be expected.

2.3 Other components The electrode slurry may contain other components as necessary in addition to the components described above. Examples of such other components include a conductivity-imparting agent, a non-aqueous medium, A thickener etc. can be mentioned.

2.3.1 Conductivity-imparting agent Specific examples of the conductivity-imparting agent include carbon in a lithium ion secondary battery;
In nickel-metal hydride secondary batteries, cobalt oxide is the positive electrode:
For the negative electrode, nickel powder, cobalt oxide, titanium oxide, carbon and the like are used. In both the batteries, examples of carbon include graphite, activated carbon, acetylene black, furnace black, graphite, carbon fiber, and fullerene. Among these, acetylene black or furnace black can be preferably used. The use ratio of the conductivity-imparting agent is preferably 20 parts by mass or less, more preferably 1 to 15 parts by mass, and particularly preferably 2 to 10 parts by mass with respect to 100 parts by mass of the active material particles.

2.3.2 Non-aqueous medium The slurry for electrodes may contain a non-aqueous medium having a standard boiling point of 80 to 350 ° C from the viewpoint of improving the coating property. Specific examples of such a non-aqueous medium include amide compounds such as N-methylpyrrolidone, dimethylformamide, N, N-dimethylacetamide;
Hydrocarbons such as toluene, xylene, n-dodecane, tetralin;
Alcohols such as 2-ethyl-1-hexanol, 1-nonanol, lauryl alcohol;
Ketones such as methyl ethyl ketone, cyclohexanone, phorone, acetophenone, isophorone;
Esters such as benzyl acetate, isopentyl butyrate, methyl lactate, ethyl lactate, butyl lactate;
amine compounds such as o-toluidine, m-toluidine, p-toluidine;
lactones such as γ-butyrolactone and δ-butyrolactone;
Examples thereof include sulfoxide and sulfone compounds such as dimethyl sulfoxide and sulfolane, and one or more selected from these compounds can be used. Among these, it is preferable to use N-methylpyrrolidone from the viewpoints of stability of polymer particles, workability when applying an electrode slurry, and the like.
However, it is preferable that the electrode slurry does not contain a non-aqueous medium from the viewpoints of reducing environmental load, ensuring worker safety, and reducing management costs.

2.3.3 Thickener The above slurry for an electrode can contain a thickener from the viewpoint of improving the coatability or further improving the charge / discharge characteristics of the obtained electricity storage device.
Examples of such thickeners include cellulose compounds such as carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose;
An ammonium salt or an alkali metal salt of the cellulose compound;
Polycarboxylic acids such as poly (meth) acrylic acid, modified poly (meth) acrylic acid;
An alkali metal salt of the polycarboxylic acid;
Vinyl alcohol (co) polymers such as polyvinyl alcohol, modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer;
Examples thereof include water-soluble polymers such as saponified products of copolymers of unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid and fumaric acid and vinyl esters. Among these, particularly preferred thickeners include alkali metal salts of carboxymethyl cellulose and alkali metal salts of poly (meth) acrylic acid.
Examples of commercially available products of these thickeners include CMC1120, CMC1150, CMC2200, CMC2280, and CMC2450 (manufactured by Daicel Corporation) as alkali metal salts of carboxymethylcellulose.
When the electrode slurry contains a thickener, the use ratio of the thickener is preferably 20% by mass or less, more preferably 0.1 to 15% by mass with respect to the total solid content of the electrode slurry. %, And more preferably 0.5 to 10% by mass.

2.4 Preferred Embodiment of Electrode Slurry The electrode slurry contains 0.1 to 10 parts by mass in terms of solid content of the electrode binder composition of the present invention with respect to 100 parts by mass of the active material. Preferably, 0.3 to 4 parts by mass is contained. When the content ratio of the electrode binder composition is 0.1 to 10 parts by mass in terms of solid content, the polymer is difficult to dissolve in the electrolytic solution used in the electricity storage device, and as a result, even at high temperatures. An adverse effect on device characteristics due to an increase in overvoltage can be suppressed.
The electrode slurry is prepared by mixing the electrode binder composition of the present invention, the active material as described above, and other components used as necessary. As a means for mixing them, for example, a known mixing device such as a stirrer, a defoamer, a bead mill, a high-pressure homogenizer, or the like can be used.
The electrode slurry is preferably prepared under reduced pressure. Thus, bubbles can be prevented from being generated in the obtained active material layer.
By containing the electrode binder composition of the present invention, the electrode slurry as described above can form an active material layer having high adhesion between active materials and between an active material and a current collector, Moreover, the electrical storage device excellent in the electrochemical stability in a high temperature environment can be provided.

3 Electrode The electrode in the present invention is
A current collector,
The active material layer formed through the process of apply | coating the slurry for electrodes demonstrated above and drying on the surface of the said electrical power collector is provided. After the coating film is dried, press working is preferably performed.

3.1 Current collector As the current collector, for example, a metal foil, an etching metal foil, an expanded metal, or the like can be used. Specific examples of these materials include metals such as aluminum, copper, nickel, tantalum, stainless steel, and titanium, and can be appropriately selected and used depending on the type of the target power storage device.
For example, when forming the positive electrode of a lithium ion secondary battery, it is preferable to use aluminum among the above as a collector. In this case, the thickness of the current collector is preferably 5 to 30 μm, and more preferably 8 to 25 μm.
On the other hand, when forming the negative electrode of a lithium ion secondary battery, it is preferable to use copper among the above as the current collector. In this case, the thickness of the current collector is preferably 5 to 30 μm, and more preferably 8 to 25 μm.
Furthermore, when forming an electrode for an electric double layer capacitor, it is preferable to use aluminum or copper among the above as the current collector. In this case, 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.

3.2 Formation of Active Material Layer The active material layer in the electrode is formed by applying an electrode slurry to the surface of the current collector as described above and drying it.
As a method for applying the electrode slurry onto the current collector, for example, an appropriate method such as a doctor blade method, a reverse roll method, a comma bar method, a gravure method, or an air knife method can be applied.
The drying treatment of the coating film is preferably performed in a temperature range of 20 to 250 ° C., more preferably 50 to 150 ° C., preferably for a processing time of 1 to 120 minutes, more preferably 5 to 60 minutes.
The dried coating film is preferably subjected to press working. Examples of means for performing the pressing include a roll press machine, a high-pressure super press machine, a soft calendar, and a 1-ton press machine. The conditions for the press working are appropriately set according to the type of processing machine used and the desired thickness and density of the active material layer.
The preferable thickness and density of the active material layer vary depending on the application.
In the case of a lithium ion secondary battery negative electrode, the thickness is preferably 40 to 100 μm and the density is preferably 1.3 to 1.9 g / cm ³ ;
In the case of a lithium ion secondary battery positive electrode, the thickness is preferably 40-100 μm and the density is preferably 2.0-5.0 g / cm ³ ; and in the case of an electric double layer capacitor electrode, the thickness is 50-200 μm. And the density is preferably 0.9 to 1.8 g / cm ³ .

4 Power Storage Device The power storage device in the present invention includes the electrode as described above.
The electricity storage device according to the present invention has a structure in which the electrode as described above is opposed to the counter electrode via the electrolytic solution, and is preferably isolated by the presence of the separator.
As a manufacturing method thereof, for example, two electrodes (two of a positive electrode and a negative electrode or two of a capacitor electrode) are overlapped via a separator, and this is wound or folded in accordance with the battery shape. And injecting the electrolyte into the battery container and sealing it. The shape of the battery can be an appropriate shape such as a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, or a flat shape.
The electrolytic solution is appropriately selected and used depending on the type of the target electricity storage device. As the electrolytic solution, a solution in which an appropriate electrolyte is dissolved in a solvent is used.
When manufacturing a lithium ion secondary battery, a lithium compound is used as an electrolyte. Specifically, for example _{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 can be given. The electrolyte concentration in this case is preferably 0.5 to 3.0 mol / L, more preferably 0.7 to 2.0 mol / L.
When manufacturing an electric double layer capacitor, for example, tetraethylammonium tetrafluoroborate, triethylmethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate or the like is used as an electrolyte. The electrolyte concentration in this case is preferably 0.5 to 3.0 mol / L, more preferably 0.7 to 2.0 mol / L.
The type and concentration of the electrolyte in manufacturing the lithium ion capacitor are the same as in the case of the lithium ion secondary battery.

In any case, examples of the solvent used in the electrolyte include carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate;
lactones such as γ-butyrolactone;
Ethers such as trimethoxysilane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran;
Sulfoxides such as dimethyl sulfoxide;
Oxolane derivatives such as 1,3-dioxolane, 4-methyl-1,3-dioxolane;
Nitrogen-containing compounds such as acetonitrile and nitromethane;
Esters such as methyl formate, methyl acetate, butyl acetate, methyl propionate, ethyl propionate, phosphate triester;
Glyme compounds such as diglyme, triglyme and tetraglyme;
Ketones such as acetone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone;
Sulfone compounds such as sulfolane;
Oxazolidinone derivatives such as 2-methyl-2-oxazolidinone;
Examples include sultone compounds such as 1,3-propane sultone, 1,4-butane sultone, 2,4-butane sultone, and 1,8-naphtha sultone.
Such an electricity storage device has high adhesion between the active materials and between the active material and the current collector in the active material layer, and is excellent in electrochemical stability in a high temperature environment. Therefore, this power storage device is suitable as a secondary battery or capacitor mounted on an automobile such as an electric vehicle, a hybrid car, or a truck, and also used as a secondary battery or a capacitor for AV equipment, OA equipment, communication equipment, etc. It is also suitable.

  Hereinafter, the present invention will be specifically described based on examples. However, the present invention is not limited to these examples.

<Preparation of polymer particles>
Synthesis example 1
(1) Synthesis of Polymer A The inside of an autoclave having an internal volume of about 6 L equipped with an electromagnetic stirrer was sufficiently purged with nitrogen. Thereafter, 2.5 L of deoxygenated pure water and 10 g of ammonium perfluorodecanoate as an emulsifier were charged into the autoclave, and the temperature was raised to 60 ° C. while stirring at 350 rpm. Next, a mixed gas consisting of 70% by mass of vinylidene fluoride (VDF) and 30% by mass of propylene hexafluoride (HFP) as monomers was charged until the internal pressure reached 20 kg / cm ² . Furthermore, 25 g of Freon 113 solution containing 20% by mass of diisopropyl peroxydicarbonate as a polymerization initiator was injected using nitrogen gas to initiate polymerization. During the polymerization, a mixed gas composed of 60.2% by mass of VDF and 39.8% by mass of HFP was sequentially injected so that the internal pressure was maintained at 20 kg / cm ² , and the pressure was maintained at 20 kg / cm ² . Further, since the polymerization rate decreased as the polymerization progressed, 3 hours after the start of polymerization, the same amount of the same polymerization initiator solution as that described above was injected using nitrogen gas, and the reaction was continued for another 3 hours. Thereafter, the reaction liquid was cooled and the stirring was stopped at the same time, and the reaction was stopped by releasing the unreacted monomer to obtain an aqueous dispersion containing 40% by mass of polymer A fine particles.
For the obtained aqueous dispersion, the particle size frequency distribution was measured using a particle size frequency distribution measuring apparatus (manufactured by Nikkiso Co., Ltd., model “NPA150”) based on the dynamic light scattering method. The determined maximum frequency diameter was 250 nm.
As a result of analyzing the obtained polymer by ¹⁹ F-NMR, the mass composition ratio of each monomer was VDF: HFP = 21: 4 (mass ratio).

(2) Synthesis of polymer particles (polymerization of polymer B)
The inside of the 7-L separable flask was thoroughly purged with nitrogen. Thereafter, 1,600 g of an aqueous dispersion containing fine particles of the polymer A obtained in (1) above (corresponding to 25 parts by mass in terms of the polymer A) in the separable flask, an emulsifier “ADEKA rear soap SR1025” (Trade name, manufactured by ADEKA Corporation) 0.5 parts by mass, methyl methacrylate (MMA) 30 parts by mass, 2-ethylhexyl acrylate (EHA) 40 parts by mass and methacrylic acid (MAA) 5 parts by mass, and water 130 parts by mass were sequentially added and stirred at 40 ° C. for 6 hours to allow the polymer A to absorb the monomer. Next, 20 mL of a tetrahydrofuran solution containing 0.5 part by mass of azobisisobutyronitrile, which is an oil-soluble polymerization initiator, is added, heated to 75 ° C., reacted for 3 hours, and further reacted at 85 ° C. for 2 hours. went. Thereafter, the reaction was stopped by cooling, and an aqueous dispersion containing 40% by mass of polymer particles (P1) was obtained by adjusting the pH to 7 by adding a 2.5N aqueous sodium hydroxide solution to the reaction mixture.
With respect to the obtained aqueous dispersion, the particle size frequency distribution was measured using a particle size frequency distribution measuring device “NPA150”, and the maximum frequency size obtained from the distribution was 500 nm.
Further, about 10 g of the obtained aqueous dispersion was taken into a Teflon (registered trademark) petri dish having a diameter of 8 cm and dried at 120 ° C. for 1 hour to form a film. 1 g of the obtained membrane (polymer) was accurately weighed and immersed in 400 mL of tetrahydrofuran (THF) and shaken at 50 ° C. for 3 hours. From the value obtained by measuring the mass (Y (g)) of the residue (dissolved component) obtained by distilling THF off after removing the insoluble component by filtering the solution after shaking with a 300-mesh wire mesh. When the THF-insoluble content was determined by the following mathematical formula (2), the THF-insoluble content of the polymer particles (P1) was 95% by mass.
THF insoluble matter (mass%) = {(1-Y) / 1} × 100 (2)
Furthermore, when the obtained fine particles were measured with a differential scanning calorimeter (DSC), the melting temperature Tm was not observed, and a single glass transition temperature Tg was observed at -2 ° C. The particles were presumed to be polymer alloy particles.

Synthesis Examples 2-4
In the synthesis example 1, “(1) Synthesis of polymer A”, the composition of the monomer gas and the amount of the emulsifier ammonium perfluorodecanoate were appropriately changed, and “(2) Synthesis of polymer particles” In Table 1, the amount of the monomer charged (parts by mass) is as shown in Table 1, so that each of the polymer particles (P2) to (P4) having the particle diameters shown in Table 1 is dispersed in water. Got the body.
Synthesis example 5
In “(2) Synthesis of polymer particles” in Synthesis Example 1 above, the aqueous dispersion containing fine particles of polymer A was not used, and the monomer charge (parts by mass) was as shown in Table 1. Further, by changing the use amount of the emulsifier, an aqueous dispersion containing polymer particles (P5) having the particle diameters shown in Table 1 was obtained.

Abbreviations of each component in Table 1 have the following meanings.
[Monomer of Polymer A]
VDF: Vinylidene fluoride HFP: Propylene hexafluoride TFE: Tetrafluoroethylene [monomer of polymer B]
MMA: Methyl methacrylate EHA: 2-ethylhexyl acrylate MAA: Methacrylic acid The notation “-” in Table 1 indicates that the corresponding component was not used or the measurement target did not exist.

Example 1
<Preparation of binder composition>
A binder composition was obtained by stirring and mixing 50 parts by mass of the aqueous dispersion (P1) obtained in Synthesis Example 1 and 50 parts by mass of the aqueous dispersion (P2) obtained in Synthesis Example 2.
When the particle size frequency distribution of the polymer particles contained in the obtained binder composition was measured with a particle size frequency distribution measuring device “NPA150”, two peaks having two peaks (maximum frequency diameter) at 50 nm and 460 nm were obtained. Particle size frequency distribution.
<Preparation of active material particles>
Commercially available lithium iron phosphate (LiFePO ₄ ) was pulverized in an agate mortar and classified using a sieve to prepare active material particles having a particle diameter (D50 value) of 0.5 μm.
<Preparation of slurry for positive electrode>
In a biaxial planetary mixer (product name “TK Hibismix 2P-03” manufactured by PRIMIX Co., Ltd.), 1 part by weight of a thickener (product name “CMC1120”, manufactured by Daicel Corporation) (in terms of solid content) ), 100 parts by mass of the active material particles prepared in “Preparation of active material particles”, 5 parts by mass of acetylene black, and 68 parts by mass of water were added, and the mixture was stirred at 60 rpm for 1 hour. Next, the binder composition prepared in “Preparation of Binder Composition” is added so that the polymer particles contained in the composition are in the amount (parts by mass) described in Table 2, and further stirred for 1 hour. To obtain a paste. After adding water to the obtained paste to adjust the solid content concentration to 50% by mass, the mixture was stirred at 200 rpm for 2 minutes at 200 rpm using a defoaming machine (trade name “Awatori Netaro”, manufactured by Shinkey Co., Ltd.). A positive electrode slurry was prepared by stirring and mixing at 1,800 rpm for 5 minutes and further under vacuum (about 5.0 × 10 ³ Pa) at 1,800 rpm for 1.5 minutes.

<Manufacture and evaluation of positive electrode and electricity storage device>
(1) Manufacture of positive electrode On the surface of a current collector made of an aluminum foil having a thickness of 30 μm, the slurry for positive electrode prepared above is uniformly applied by a doctor blade method so that the film thickness after drying becomes 100 μm. Dry at 20 ° C. for 20 minutes. Then, the positive electrode was obtained by pressing with a roll press so that the density of a film | membrane (active material layer) might become the value as described in Table 2.
(2) Evaluation of adhesion strength of positive electrode <Evaluation of powder fall resistance>
Five samples of 10 cm × 5 cm were cut out from the positive electrode manufactured in the above item (1), and they were overlapped. A commercially available high-quality paper was placed on the experimental table, and a 100 mesh stainless steel mesh was placed thereon. The above five electrode test pieces stacked on the mesh were cut nine times at intervals of 1 cm from the end in a direction perpendicular to the long side using scissors to obtain 10 pieces of 1 cm × 5 cm. At this time, the presence or absence of the active material powder which passed through the stainless steel mesh and spilled on the fine paper was examined. Based on the results, powder fall resistance was evaluated according to the following criteria. The results of this dust-off resistance are shown in Table 2.
Good: When there was no powder falling. Poor: When even a small amount of powder was observed <Evaluation of binding force>
Five samples of 10 cm square were cut out from the positive electrode produced in the above item (1), and each sample was compressed by a hot press at 120 ° C. for 5 minutes. On the surface of each electrode after compression, using a knife, 6 incisions with a depth reaching the current collector from the active material layer were made at intervals of 2 mm to make 25 incisions in a grid pattern. The adhesive tape (trade name: cello tape, model number: CT18-S, manufactured by Nichiban Co., Ltd.) was applied to the entire surface of the cut portion, and then immediately peeled off. At this time, the number of squares of the active material layer peeled from the copper foil was counted.
The above operation was carried out once for each sample (one side), and the number of squares peeled out of a total of 125 squares of a total of 5 samples was counted, and this number was evaluated according to the following criteria. The results are shown in Table 2.
Good: When the dropped mass is 0 to 5 Poor: When the dropped mass is 6 or more

(3) Manufacture of negative electrode In biaxial planetary mixer (product name "TK Hibismix 2P-03" manufactured by PRIMIX Co., Ltd.), 4 parts by mass of polyvinylidene fluoride (PVDF) (solid content conversion), negative electrode active As materials, 100 parts by mass of graphite (in terms of solid content) and 80 parts by mass of N-methylpyrrolidone (NMP) were added and stirred at 60 rpm for 1 hour. Then, after further adding 20 parts by mass of NMP, using a stirring deaerator (manufactured by Shinky Co., Ltd., product name “Awatori Neritaro”) for 2 minutes at 200 rpm, then for 5 minutes at 1,800 rpm, A negative electrode slurry was prepared by stirring and mixing at 1,800 rpm for 1.5 minutes under vacuum.
The negative electrode slurry prepared above was uniformly applied to the surface of a current collector made of copper foil having a thickness of 20 μm by a doctor blade method so that the film thickness after drying was 150 μm, and dried at 120 ° C. for 20 minutes. . Then, the negative electrode was obtained by pressing using a roll-press machine so that the density of a film | membrane may be 1.5 g / cm < ³ >.
(4) Lithium-ion battery cell assembly In a glove box substituted with Ar so that the dew point is −80 ° C. or less, the negative electrode manufactured in “(2) Manufacturing of negative electrode” was punched and molded to a diameter of 16.16 mm. The product was placed on a bipolar coin cell (trade name “HS Flat Cell” manufactured by Hosen Co., Ltd.). Next, a separator made of a polypropylene porous membrane punched to a diameter of 24 mm (manufactured by Polypore Co., Ltd., trade name “Celguard # 2400”) is placed, and further, 500 μL of electrolyte is injected so that air does not enter, A lithium ion battery is manufactured by placing the positive electrode manufactured in the above-mentioned “(1) Manufacturing of positive electrode” by punching and molding the positive electrode to a diameter of 15.95 mm, and sealing the outer body of the two-pole coin cell with a screw. A cell (electric storage device) was assembled.
The electrolytic solution used here is a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate: ethyl methyl carbonate = 1: 1 (mass ratio).

(5) Evaluation of electricity storage device (Evaluation of charge / discharge rate characteristics)
About the electrical storage device manufactured above, charging is started at a constant current (0.2 C), and when the voltage reaches 4.2 V, charging is continued at a constant voltage (4.2 V). The charging capacity at 0.2 C was measured with the time when 0.01 C was reached as the completion of charging (cut-off). Next, discharge was started at a constant current (0.2 C), and when the voltage reached 2.7 V, the discharge was completed (cut off), and the discharge capacity at 0.2 C was measured.
Next, charging is started at a constant current (3C) for the same cell, and when the voltage reaches 4.2V, charging is continued at a constant voltage (4.2V). The charging capacity at 3C was measured with the point of time when charging was completed (cut-off). Next, discharge was started at a constant current (3C), and when the voltage reached 2.7 V, the discharge was completed (cut-off), and the discharge capacity at 3C was measured.
Using the above measured value, the charge rate (%) is calculated by calculating the ratio (percent%) of the charge capacity at 3C to the charge capacity at 0.2C.
The discharge rate (%) was calculated by calculating the ratio (percentage) of the discharge capacity at 3C to the discharge capacity at 0.2C.
When both the charge rate and the discharge rate are 80% or more, it can be evaluated that the charge / discharge rate characteristics are good.
The measured charge rate and discharge rate values are shown in Table 2, respectively.
In the measurement conditions, “1C” indicates a current value at which discharge is completed in one hour after constant current discharge of a cell having a certain electric capacity. For example, “0.1 C” is a current value at which discharge is completed over 10 hours, and 10 C is a current value at which discharge is completed over 0.1 hours.

Examples 2-9 and Comparative Examples 1-6
<Preparation of binder composition>
In <Preparation of Binder Composition> in Example 1 above, the amount of polymer particles listed in Table 2 was used as the aqueous dispersion in the amount (parts by mass) listed in Table 2. A binder composition was prepared in the same manner as in Example 1, and a positive electrode and an electricity storage device were produced and evaluated using the binder composition. The evaluation results are shown in Table 2.
In Comparative Examples 2 to 6, one type of aqueous dispersion was used for each.
A particle size frequency distribution chart of the polymer particles in each binder composition obtained in Example 2 and Comparative Example 3 measured by a particle size frequency distribution measuring apparatus “NPA150” is shown in FIGS. 1 and 2, respectively.
In Table 2, among the polymer particles contained in each of the aqueous dispersions used, the polymer particle having the larger maximum frequency diameter is “particle 1”, and the polymer particle having the smaller maximum frequency diameter is “particle” 2 ”.

The notation "-" in Table 2 indicates that the corresponding component was not used or the measurement object did not exist.

Claims (6)

A binder composition for an electrode containing polymer particles and a liquid medium ,
Ri particle diameter frequency distribution is bimodal der measured by dynamic light scattering method for the previous SL polymer particles, and
The polymer belonging to at least one of two peaks in the particle size frequency distribution of the polymer particles,
A polymer A having a repeating unit derived from at least one selected from the group consisting of vinylidene fluoride, ethylene tetrafluoride and propylene hexafluoride;
A polymer B having a repeating unit derived from an unsaturated carboxylic acid ester;
Oh a polymer alloy particles consisting Rukoto, characterized in, the electrode binder composition. The polymer alloy particles are
A step of starting polymerization of the polymer B after adding a monomer for constituting the polymer B to the liquid medium containing the polymer A and maintaining the polymer B at 30 to 100 ° C. for 1 to 12 hours. it is those prepared, electrode binder composition of claim 1. The bimodal sac Chi constituting the particle size distribution of the polymer particles,
1 Peak is peaks having the maximum frequency diameter in the range of 40 to 100 nm,
Ru peaks der having a maximum frequency diameter other peak is in the range of 200 to 500 nm, according to claim 1 or electrode binder composition described in 2. The polymer particles are
The binder composition for electrodes according to any one of claims 1 to 3, which is a mixture composed of a plurality of polymer particles having a unimodal particle size distribution measured by a dynamic light scattering method.   It manufactured using the binder composition for electrodes as described in any one of Claims 1-3, The positive electrode of the electrical storage device characterized by the above-mentioned. An electrical storage device comprising the positive electrode according to claim 5 .

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