JP6065150B1 - Storage method for binder composition for electricity storage device electrode - Google Patents

Abstract

An excellent storage stability of a binder composition for an electricity storage device electrode, which contains at least one polymer selected from the group consisting of polyamic acids, polyamic acid derivatives, and imidized polymers thereof, and water. Provide a safe storage method. A storage method of a binder composition for an electricity storage device electrode according to the present invention includes (A) at least one polymer selected from the group consisting of polyamic acid, polyamic acid derivatives, and imidized polymers thereof. And a method for storing the binder composition for an electricity storage device electrode containing water in a container, wherein the void portion excluding the volume occupied by the binder composition for an electricity storage device electrode with respect to the internal volume of the container The volume ratio is 1 to 20%, and the volume is stored at a temperature of 0 ° C. or higher and 40 ° C. or lower. [Selection figure] None

Description

  The present invention relates to a method for storing a binder composition for an electricity storage device electrode.

  In recent years, a power storage device having a high voltage and a high energy density has been required as a power source for driving electronic equipment. In particular, lithium ion batteries and lithium ion capacitors are expected as power storage devices having high voltage and high energy density.

  The electrode used for an electrical storage device is normally manufactured by apply | coating and drying the composition (slurry for electrodes) containing an active material and the polymer which functions as a binder to the collector surface. The properties required for the polymer used as the binder for the electrode include the ability to bind the active materials and the adhesion between the active material and the current collector, the abrasion resistance in the step of winding the electrode, and subsequent cutting. In addition, there may be mentioned powder-off resistance in which fine powder of the active material does not fall off from the applied and dried composition coating film (hereinafter also simply referred to as “electrode mixture layer”). When the polymer satisfies these various required characteristics, the degree of freedom in structural design of the electricity storage device such as the method of folding the obtained electrode and setting the winding radius is increased, and the device can be miniaturized. it can.

  In addition, it has been empirically clarified that the quality of the active materials is substantially proportional to the ability to bond the active materials to each other, the ability to adhere the active material to the current collector, and the powder-off resistance. Therefore, in the present specification, hereinafter, the term “adhesiveness” may be used in a comprehensive manner.

  In recent years, in order to achieve the demand for higher output and higher energy density of such an electricity storage device, studies are being made to apply a material having a large lithium storage capacity. For example, silicon can reversibly store and release lithium by forming an intermetallic compound with lithium (see, for example, Patent Document 1). The theoretical capacity of silicon is about 4,200 mAh / g at the maximum, which is extremely large compared with the theoretical capacity of about 370 mAh / g of the conventionally used carbon material. Device capacity should be greatly improved. However, since the volume change due to charging / discharging is large in silicon materials, when the binder material used in the past is applied to silicon materials, the initial adhesion cannot be maintained, and the capacity decreases significantly with charging / discharging. Will occur.

  A method of using polyimide as an electrode binder for holding such a silicon material in an electrode mixture layer has been proposed (see, for example, Patent Documents 2 to 4). These techniques are technical ideas of restraining the volume change of a silicon material by constraining the silicon material with a rigid molecular structure of polyimide. In Patent Documents 2 to 4, by applying a slurry for negative electrode containing polyamic acid to the current collector surface to form a coating film, the coating film is heated at a high temperature to thermally imidize the polyamic acid. Techniques for forming polyimide are disclosed.

  Each of these binders using polyimide is obtained by dissolving a binder component in N-methyl-2-pyrrolidone (NMP). On the other hand, in the negative electrode of the electricity storage device, there is an increasing demand for an aqueous binder from the viewpoint of cost reduction, environmental load reduction, and battery characteristic improvement.

JP 2004-185810 A JP 2007-95670 A JP 2011-192563 A JP 2011-205942 A

  However, it is known that polyamic acid as a binder component, polyimide obtained by imidizing this, or a mixture thereof are potentially hydrolyzed in the presence of water. In addition, since the main chain of the polymer is broken by hydrolysis and the formation of new amide and imide bonds occurs repeatedly, the binder composition may cause a significant change in viscosity, or aggregates may precipitate over time and There was a case. The electrode mixture layer produced using the binder composition containing the foreign matter thus generated has a non-uniform structure, and the electricity storage device produced using this has a short circuit due to local excessive resistance or ignition. May cause. Moreover, since the amine residue produced | generated with a hydrolysis is easily oxidized to a nitro group with oxygen, the external appearance of the aqueous solution containing a binder component will change remarkably. Further, these binder components are deteriorated by light irradiation, and original mechanical properties such as elastic modulus are deteriorated. Therefore, a method that can stably store an aqueous binder containing a polyamic acid or a polyimide obtained by imidizing the polyamic acid has been desired.

  Accordingly, some embodiments according to the present invention solve at least a part of the above-described problems, thereby at least one heavy selected from the group consisting of polyamic acid, polyamic acid derivatives, and imidized polymers thereof. Provided is a storage method excellent in storage stability of an aqueous binder composition containing a coalescence.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
One aspect of the storage method of the binder composition for an electricity storage device electrode according to the present invention,
(A) Filling a container with a binder composition for an electricity storage device electrode containing at least one polymer selected from the group consisting of a polyamic acid, a polyamic acid derivative, and an imidized polymer thereof, and water. A storage method,
The ratio of the volume of the void portion excluding the volume occupied by the binder composition for an electricity storage device electrode to the internal volume of the container is 1 to 20%, and the container is stored at a temperature of 0 ° C. or higher and 40 ° C. or lower.

[Application Example 2]
In the storage method of Application Example 1,
The container may be a light shielding container.

[Application Example 3]
In the storage method of Application Example 1 or Application Example 2,
The electrical storage device electrode binder composition may have a pH of 5 to 11.

[Application Example 4]
In the storage method of any one of application examples 1 to 3,
The electrical conductivity of the water may be 1,000 μS / cm or less.

[Application Example 5]
In the storage method of any one of application examples 1 to 4,
The binder composition for an electricity storage device electrode further comprises (B) N-methylpyrrolidone, N-ethylpyrrolidone, γ-butyrolactone, N, N-dimethylacetamide, butyrocellosolve, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, It may contain at least one compound selected from the group consisting of propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, propylene glycol-1-monomethyl ether-2-acetate, aliphatic ethers and aliphatic alcohols.

[Application Example 6]
In the storage method of application example 5,
In the binder composition for an electricity storage device electrode, when the content of the polymer (A) is Ma parts by mass and the content of the compound (B) is Mb parts by mass, the ratio Ma / Mb between them is 50 to 50 parts. It can be 5,000.

[Application Example 7]
In the storage method of any one of application examples 1 to 6,
The binder composition for an electricity storage device electrode may further contain (C) an isothiazoline compound, and the concentration of the (C) isothiazoline compound in the binder composition may be 15 ppm or more and 500 ppm or less.

  According to the storage method of the binder composition for an electricity storage device electrode according to the present invention, an aqueous binder containing at least one polymer selected from the group consisting of polyamic acid, polyamic acid derivatives, and imidized polymers thereof. Since the storage stability of the composition becomes good, it is possible to provide an aqueous binder composition with stable quality at any time. As a result, the electrode yield can be improved.

  Hereinafter, preferred embodiments according to 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 modifications that are implemented without departing from the scope of the present invention. Hereinafter, it demonstrates in order of the binder composition for electrical storage device electrodes suitable for the storage method of this invention, and its storage method.

1. Binder composition for an electricity storage device electrode The binder composition for an electricity storage device electrode used in this embodiment (hereinafter, also simply referred to as “aqueous binder composition”) is (A) a polyamic acid, a polyamic acid derivative, and an imide thereof. And at least one polymer selected from the group consisting of chemical polymers (hereinafter also simply referred to as “component (A)”) and water. This aqueous binder composition is used as a material for producing an electricity storage device electrode (electrode mixture layer) with improved binding ability between active materials, adhesion ability between an active material and a current collector, and powder fall resistance. be able to. Hereinafter, each component contained in the aqueous binder composition used in the present embodiment will be described in detail.

1.1. (A) Component The aqueous binder composition used in the present embodiment contains (A) at least one polymer selected from the group consisting of polyamic acid, polyamic acid derivatives, and imidized polymers thereof. The component (A) may be only a polyamic acid and / or a polyamic acid derivative, but the imidized polymer obtained by subjecting the polyamic acid and / or the polyamic acid derivative to a dehydration ring-closing reaction (imidation reaction) by heating or using a catalyst. Coalescence may be included. (A
) Component has a function as a binder for improving the binding ability between active materials, the adhesion ability between the active material and the current collector, and the powder fall resistance in the electrode mixture layer constituting the electricity storage device electrode.

  Examples of the polyamic acid derivative include polyamic acid esters synthesized by esterification of polyamic acid and the like, as well as polyamic acids and salts of polyamic acid esters.

  When a part of the polyamic acid and / or polyamic acid derivative contained in the aqueous binder composition is imidized, the imidization ratio of the polyamic acid and / or polyamic acid derivative is not particularly limited, It is preferably 90% or less, more preferably 80% or less, even more preferably 70% or less, and particularly preferably 50% or less. By setting the imidization rate of the polyamic acid and / or polyamic acid derivative contained in the aqueous binder composition within the above range, the stability of the slurry for the electricity storage device electrode prepared using the binder composition is improved. Therefore, an electricity storage device electrode having excellent adhesion and charge / discharge characteristics can be produced, which is preferable.

  In the case where the aqueous binder composition contains an imidized polymer of polyamic acid and / or polyamic acid derivative, the imidization rate is preferably 80% or more, more preferably 85% or more, and 90% or more. More preferably. Since an imidized polymer having an imidization ratio in the above range has high elasticity, an electricity storage device electrode excellent in adhesion and charge / discharge characteristics can be produced.

  When the component (A) contains an imidized polymer of polyamic acid and / or polyamic acid derivative, and the imidization rate of the imidized polymer is within the above preferred range, the polyamic acid and / or polyamic acid derivative The ratio of use with the imidized polymer can be any ratio.

This imidation ratio represents the ratio of the number of imide ring structures to the total of the number of amic acid structures and the number of imide ring structures of the polyamic acid and / or polyamic acid derivative, expressed as a percentage. The imidation ratio of a polyamic acid and / or a polyamic acid derivative can be determined using ¹ H-NMR.

  The polyamic acid as the component (A) can be obtained by reacting tetracarboxylic dianhydride and diamine. (A) The polyamic acid ester which is one of the polyamic acid derivatives as the component can be synthesized by esterifying at least a part of the carboxyl group of the polyamic acid. The imidized polymer of the polyamic acid and / or polyamic acid derivative as the component (A) is imidized by dehydrating and cyclizing a part of the amic acid structure of the polyamic acid and / or polyamic acid derivative with heating or using a catalyst. Can be obtained.

Examples of the tetracarboxylic dianhydride used for synthesizing the polyamic acid or polyamic acid derivative used in the present invention include aliphatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, aromatic tetra Examples thereof include carboxylic dianhydrides. Examples of the aliphatic tetracarboxylic dianhydride include butanetetracarboxylic dianhydride; and examples of the alicyclic tetracarboxylic dianhydride include 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride. Anhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 1,3,3a, 4,5,9b-hexahydro-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1 , 2-c] furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-8-methyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1 , 2-c] furan-1,3-dione, 3-oxabicyclo [3.2.1] octane-2,4-dione-6-spiro-3 ′-(tetrahydrofuran-2 ′, 5′-dione) , 5- (2,5 Dioxotetrahydro-3-furanyl) -3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 3,5,6-tricarboxy-2-carboxymethylnorbornane-2: 3,5: 6-2 Anhydride, 2,4,6,8-tetracarboxybicyclo [3.3.0] octane-2: 4,6: 8-dianhydride, 4,9-dioxatricyclo [5.3.1. 02,6] undecane-3,5,8,10-tetraone, etc .; Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetra Carboxylic dianhydride, 3,3′4,4′-diphenylsulfone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4 '-Biphenyltetracarboxylic dianhydride , 2,2 ', and 3,3'-biphenyltetracarboxylic dianhydride, addition may be mentioned respectively, can be used tetracarboxylic acid dianhydride described in JP-A-2010-97188.

  Among tetracarboxylic dianhydrides used for synthesizing these polyamic acids or polyamic acid derivatives, those containing aromatic tetracarboxylic dianhydrides are preferred. The tetracarboxylic dianhydride used for synthesizing the polyamic acid or polyamic acid derivative used in the present invention is composed of only the aromatic tetracarboxylic dianhydride, or the aromatic tetracarboxylic dianhydride and the fat. It is preferable from a viewpoint of stability of a binder composition that it consists only of the mixture of cyclic tetracarboxylic dianhydride. In the latter case, the use ratio of the alicyclic tetracarboxylic dianhydride is preferably 30 mol% or less and preferably 20 mol% or less with respect to 100 mol% of all tetracarboxylic dianhydrides. More preferred.

Examples of the diamine used for synthesizing the polyamic acid or polyamic acid derivative used in the present invention include aliphatic diamine, alicyclic diamine, aromatic diamine, and diaminoorganosiloxane. Examples of the aliphatic diamine include 1,1-metaxylylenediamine, 1,3-propanediamine, tetramethylene diamine, pentamethylene diamine, and hexamethylene diamine. Examples of the alicyclic diamine include 1,4. -Diaminocyclohexane, 4,4'-methylenebis (cyclohexylamine), 1,3-bis (aminomethyl) cyclohexane and the like; examples of the aromatic diamine include p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4 , 4′-diaminodiphenyl sulfide, 1,5-diaminonaphthalene, 2,2′-dimethyl-4,4′-diaminobiphenyl, 4,4′-diamino-2,2′-bis (trifluoromethyl) biphenyl, 2,7-diaminofluorene, 4,4'-diaminodiphenyl ether 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 9,9-bis (4-aminophenyl) fluorene, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoro Propane, 2,2-bis (4-aminophenyl) hexafluoropropane, 4,4 ′-(p-phenylenediisopropylidene) bisaniline, 4,4 ′-(m-phenylenediisopropylidene) bisaniline, 1,4 -Bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, 2,6-diaminopyridine, 3,4-diaminopyridine, 2,4-diaminopyrimidine, 3,6-diamino Acridine, 3,6-diaminocarbazole, N-methyl-3,6-diaminocarbazole, N-ethyl-3,6-diaminocarb Rubazole, N-phenyl-3,6-diaminocarbazole, N, N′-bis (4-aminophenyl) -benzidine, N, N′-bis (4-aminophenyl) -N, N′-dimethylbenzidine, 1 , 4-bis- (4-aminophenyl) -piperazine, 3,5-diaminobenzoic acid, etc .; examples of the diaminoorganosiloxane include 1,3-bis (3-aminopropyl) -tetramethyldisiloxane, In addition to these, diamines described in JP 2010-97188 A can be used. The diamine used when synthesizing the polyamic acid and / or the polyamic acid derivative is preferably one containing 30 mol% or more, and 50 mol% or more of the aromatic diamine with respect to 100 mol% of the total diamine. More preferably, it is particularly preferably one containing 80 mol% or more.

  When synthesizing the polyamic acid or polyamic acid derivative used in the present invention, a terminal-modified polymer may be synthesized using a suitable molecular weight regulator together with tetracarboxylic dianhydride and dimian.

  As said molecular weight regulator, an acid monoanhydride, a monoamine compound, a monoisocyanate compound etc. can be mentioned, for example. Examples of the acid monoanhydride include maleic anhydride, phthalic anhydride, itaconic anhydride, n-decyl succinic anhydride, n-dodecyl succinic anhydride, n-tetradecyl succinic anhydride, n-hexadecyl succinic acid. Examples of monoamine compounds include aniline, cyclohexylamine, n-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, and n-octylamine; examples of monoisocyanate compounds include phenyl Examples thereof include isocyanate and naphthyl isocyanate.

  The use ratio of the molecular weight regulator is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, with respect to 100 parts by mass in total of the tetracarboxylic dianhydride and diamine to be used.

  The ratio of tetracarboxylic dianhydride and diamine used for the synthesis reaction of polyamic acid or polyamic acid derivative is such that the acid anhydride group of tetracarboxylic dianhydride is 0 with respect to 1 equivalent of amino group of diamine. The ratio which becomes 0.9-1.2 equivalent is preferable, and the ratio which becomes 1.0-1.1 equivalent is more preferable.

  The synthesis reaction of the polyamic acid or polyamic acid derivative is preferably performed in an organic solvent, preferably at −20 ° C. to 150 ° C., more preferably at 0 to 100 ° C., preferably 0.1 to 24 hours, more preferably 0. 5 to 12 hours.

Here, as the organic solvent, for example, an aprotic polar solvent, a phenol and a derivative thereof, an alcohol, a ketone, an ether, an ester, a hydrocarbon, or the like, which can be generally used for a polyamic acid synthesis reaction, can be used. . Examples of the aprotic polar solvent include N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, Nt-butyl-2-pyrrolidone, N-methoxyethyl-2-pyrrolidone, N, N-dimethyl. Acetamide, N, N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, tetramethylurea, hexamethylphosphortriamide and the like; examples of the phenol derivative include m-cresol, xylenol, halogenated phenol and the like; For example, methanol, ethanol, isopropanol, cyclohexanol, ethylene glycol, propylene glycol, 1,4-butanediol, triethylene glycol, ethylene glycol monomethyl ether, etc .; And ether such as dimethyl ether, methyl ethyl ether, diethyl ether, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-i- Propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol di-n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol ethyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl Examples include ruether acetate, diethylene glycol monoethyl ether acetate, tetrahydrofuran, tetrahydropyran, and furan. Examples of the ester include ethyl lactate, butyl lactate, methyl acetate, ethyl acetate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate, isoamyl propionate, isoamyl isobutyrate, diethyl oxalate, and malon. Examples of the hydrocarbon include diethyl acid and the like. Examples of the hydrocarbon include hexane, heptane, octane, benzene, toluene, xylene and the like. These organic solvents may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  The dehydration ring closure reaction of the polyamic acid or polyamic acid derivative is preferably a method of heating the polyamic acid or polyamic acid derivative or adding a dehydrating agent and a dehydrating ring closure catalyst in a solution in which the polyamic acid or polyamic acid derivative is dissolved in an organic solvent. Depending on the heating method.

  The reaction temperature in the method of heating the polyamic acid or polyamic acid derivative is preferably 140 to 250 ° C, more preferably 180 to 220 ° C. When the reaction temperature is less than 140 ° C., the dehydration ring-closing reaction does not proceed sufficiently, and when the reaction temperature exceeds 250 ° C., the molecular weight of the imidized polymer obtained may decrease. The reaction time in the method of heating the polyamic acid or polyamic acid derivative is preferably 0.5 to 20 hours, more preferably 2 to 10 hours.

  In the method of adding a dehydrating agent and a dehydrating ring-closing catalyst in the polyamic acid and / or polyamic acid derivative solution, an acid anhydride such as acetic anhydride, propionic anhydride, or trifluoroacetic anhydride is used as the dehydrating agent. Can do. It is preferable that the usage-amount of a dehydrating agent shall be 0.01-1.0 mol with respect to 1 mol of the amic acid structure of a polyamic acid and / or a polyamic acid derivative. As the dehydration ring closure catalyst, for example, amines such as pyridine, collidine, lutidine, isoquinoline, and triethylamine can be used. The use ratio of the dehydration ring closure catalyst is preferably 0.01 to 1.0 mol per 1 mol of the dehydrating agent to be used. Examples of the organic solvent used for the dehydration ring closure reaction include the organic solvents exemplified as those used for the synthesis of polyamic acid or polyamic acid derivatives. The reaction temperature of the dehydration ring closure reaction is preferably 0 to 180 ° C, more preferably 10 to 180 ° C. The reaction time is preferably 1 to 10 hours, more preferably 2 to 5 hours.

  Moreover, it is preferable that the polystyrene conversion weight average molecular weight (Mw) measured by the gel permeation chromatography (GPC) is 1,000-500,000 about the (A) component obtained as mentioned above. It is more preferable that it is 1,000-300,000. Furthermore, the ratio (Mw / Mn) between the Mw and the polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is preferably 15 or less, and more preferably 10 or less. .

  The component (A) obtained as described above is used for the preparation of a slurry for an electricity storage device electrode described later as it is or after purification by a known method as necessary.

  As the component (A), a commercially available polyamic acid solution may be used. As a commercially available polyamic acid solution, U-varnish A (made by Ube Industries, Ltd.) etc. can be mentioned, for example.

1.2. Water The binder composition for an electricity storage device electrode used in the present embodiment contains water as a liquid medium. Water functions as a solvent for the component (A) and can dissolve the component (A). In addition, the slurry for an electricity storage device electrode to be described later functions as a dispersion medium for the active material and can disperse the active material.

  As the water contained in the aqueous binder composition, it is preferable to use water having an electric conductivity of 1000 μS / cm or less. That is, water having an electric conductivity of 1000 μS / cm or less is preferably used in a stage before mixing with other components. Such ionic conductivity is preferably 500 μS / cm or less, and more preferably 100 μS / cm or less. Water having such a low electrical conductivity can be obtained by purification by a purification method such as ion exchange resin or distillation.

  Such a value of electrical conductivity can be used as an indicator of the residual amount of metal ions. Therefore, aggregation of the active material due to metal ions in the electrode slurry obtained by mixing the aqueous binder composition and the active material can be suppressed by using water having low electrical conductivity. Thereby, it is possible to obtain an electrode having excellent characteristics such as less precipitation of electrolyte components such as lithium ions on the electrode surface even at low temperatures, low resistance, and excellent adhesion to the current collector. An electricity storage device having excellent characteristics such as excellent cycle characteristics and low-temperature output characteristics can be obtained.

  Moreover, as water contained in a water-based binder composition, it is preferable to use the thing whose chloride ion content rate is 0.001-0.1 mass%. That is, it is preferable to use water having a chloride ion content of 0.001 to 0.1% by mass before mixing with other components. By using such water, aggregation of the active material in the obtained electrode slurry can be suppressed, and the internal resistance of the battery can be reduced.

  The water content in the aqueous binder composition can be appropriately adjusted so as to have a concentration and viscosity suitable for the production of the electrode slurry. Specifically, the concentration of the solid content in the electrode slurry (that is, the substance remaining as a constituent component of the electrode mixture layer after drying of the electrode slurry) is preferably 40% by mass or more, more preferably 45% by mass. % And preferably adjusted to an amount of 60% by mass or less, more preferably 55% by mass or less.

1.3. Other components 1.3.1. (B) Component The aqueous binder composition used in this embodiment is (B) N-methylpyrrolidone, N-ethylpyrrolidone, γ-butyrolactone, N, N-dimethylacetamide, butyrocellosolve, ethylene glycol monobutyl ether, diethylene glycol Containing at least one compound selected from the group consisting of monoethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, propylene glycol-1-monomethyl ether-2-acetate, aliphatic ethers and aliphatic alcohols Is preferred. In the present invention, the term “aliphatic” is used in the sense of excluding aromatics.

  The aliphatic ether may be linear or cyclic. Examples of the aliphatic ether include chain ethers such as diethyl ether, dimethyl ether, methyl ethyl ether, and diethyl ether; and cyclic ethers such as tetrahydrofuran and tetrahydropyran. Among these, diethyl ether and tetrahydrofuran are preferable from the viewpoint of solubility of the component (A).

The aliphatic alcohol may be linear or cyclic. Examples of the aliphatic alcohol include methanol, ethanol, isopropanol, cyclohexanol, ethylene glycol, propylene glycol, 1,4-butanediol, triethylene glycol, ethylene glycol monomethyl ether, and the like. Among these, methanol and ethanol are preferable from the viewpoint of solubility of the component (A).

  These (B) components may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  The content ratio of the component (B) in the binder composition used in the present embodiment is when the content of the component (B) in the composition is Mb parts by mass and the content of the component (A) is Ma parts by mass. Further, the ratio Ma / Mb of both is 50 to 5,000, preferably 100 to 4,000, and more preferably 130 to 3,500. When the content rate of (B) component exists in the said range, it is guessed that the binder composition which concerns on this embodiment has the following effects.

  When the content ratio of the component (B) is within the above range, the affinity between the liquid medium constituting the aqueous binder composition and the component (A) can be increased. That is, the component (A) has poor water solubility, but the component (B) has high polarity and high affinity for the component (A). Therefore, by containing the component (B) in the above-mentioned predetermined ratio with respect to the component (A), the solubility of the component (A) in water can be increased, so that the component (A) precipitates over time. It is possible to greatly reduce the foreign matter generated by aggregation. That is, the storage stability of the aqueous binder composition is improved.

1.3.2. (C) Component The aqueous binder composition used in the present embodiment may contain (C) an isothiazoline-based compound at a concentration of 15 ppm to 500 ppm. The concentration of the component (C) in the aqueous binder composition is preferably 20 ppm to 400 ppm, more preferably 50 ppm to 300 ppm. When the concentration of the component (C) in the binder composition is within the above range, the component (C) acts as a preservative, and when the aqueous binder composition is stored, bacteria, sputum, etc. grow and foreign matter Can be prevented from occurring. Moreover, since deterioration of the binder is suppressed at the time of charge / discharge of the power storage device, it is possible to suppress a decrease in charge / discharge characteristics of the power storage device.

  The manifestation mechanism of the effect of suppressing the deterioration of the binder during charging / discharging of the electricity storage device is not clear, but is considered as follows. Since the affinity between the component (C) and the component (A) is good, the component (C) is adsorbed by the component (A) that functions as a binder even when the electrode mixture layer is immersed in the electrolytic solution. It is thought that the electrode mixture layer hardly elutes into the electrolyte solution. (C) Since component (A) is retained in component (A), deterioration of the component (A), which functions as a binder, due to the electrolyte is suppressed and deterioration of the electrolyte itself is also suppressed. It is guessed that can be suppressed.

  The component (C) used in the present invention is not particularly limited as long as it is a compound having an isothiazoline skeleton, but specifically, it is represented by the compound represented by the following general formula (1) or the following general formula (2). Compounds.

上記一般式（１）中、Ｒ^１は水素原子または炭化水素基であり、Ｒ^２及びＲ^３はそれぞ
れ水素原子、ハロゲン原子又は炭化水素基を表す。Ｒ^１、Ｒ^２、Ｒ^３が炭化水素基である場合、直鎖あるいは分岐鎖のような鎖状の炭素骨格を有していてもよく、環状の炭素骨格を有していてもよい。また、炭化水素基の炭素数は１〜１２であることが好ましく、１〜１０であることがより好ましく、１〜８であることが特に好ましい。このような炭化水素基の具体例としては、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、ヘキシル基、シクロヘキシル基、オクチル基、２−エチルヘキシル基等が挙げられる。

In the general formula (1), R ¹ is a hydrogen atom or a hydrocarbon group, and R ² and R ³ each represent a hydrogen atom, a halogen atom or a hydrocarbon group. When R ¹ , R ² and R ³ are hydrocarbon groups, they may have a linear or branched carbon skeleton, or may have a cyclic carbon skeleton. Moreover, it is preferable that carbon number of a hydrocarbon group is 1-12, it is more preferable that it is 1-10, and it is especially preferable that it is 1-8. Specific examples of such a hydrocarbon group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a hexyl group, a cyclohexyl group, an octyl group, and a 2-ethylhexyl group.

上記一般式（２）中、Ｒ^４は水素原子または炭化水素基であり、Ｒ^５はそれぞれ独立に水素原子又は有機基を表す。Ｒ^４が炭化水素基である場合、上記一般式（１）で説明した炭化水素基と同様の炭化水素基であることができる。また、Ｒ^５が有機基である場合、この有機基にはアルキル基やシクロアルキル基である脂肪族基や芳香族基が含まれるが、脂肪族基であることが好ましい。アルキル基の炭素数は１〜１２であることが好ましく、１〜１０であることがより好ましく、１〜８であることが特に好ましい。これらのアルキル基及びシクロアルキル基は、ハロゲン原子、アルコキシル基、ジアルキルアミノ基、アシル基、アルコキシカルボニル基等の置換基を有していてもよい。前記脂肪族基の具体例としては、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、ヘキシル基、シクロヘキシル基、オクチル基、２−エチルヘキシル基等が挙げられる。上記一般式（２）中、ｎは０〜４の整数を表す。

In the general formula (2), R ⁴ is a hydrogen atom or a hydrocarbon group, and R ⁵ independently represents a hydrogen atom or an organic group. When R ⁴ is a hydrocarbon group, it can be the same hydrocarbon group as the hydrocarbon group described in the general formula (1). When R ⁵ is an organic group, the organic group includes an aliphatic group or an aromatic group that is an alkyl group or a cycloalkyl group, and is preferably an aliphatic group. The alkyl group preferably has 1 to 12 carbon atoms, more preferably 1 to 10 carbon atoms, and particularly preferably 1 to 8 carbon atoms. These alkyl groups and cycloalkyl groups may have a substituent such as a halogen atom, an alkoxyl group, a dialkylamino group, an acyl group, or an alkoxycarbonyl group. Specific examples of the aliphatic group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a hexyl group, a cyclohexyl group, an octyl group, and a 2-ethylhexyl group. In said general formula (2), n represents the integer of 0-4.

  Specific examples of the component (C) used in the present invention include 1,2-benzisothiazolin-3-one, 2-methyl-4,5-trimethylene-4-isothiazolin-3-one, and 2-methyl-4- Isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, Nn-butyl-1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazoline-3 -One, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one, and the like, and one or more of these can be used. Among these, 2-methyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 1,2- It is preferably at least one selected from the group consisting of benzisothiazolin-3-one.

1.4. PH of binder composition for electricity storage device electrode
The pH of the aqueous binder composition used in the present embodiment is preferably from 3.0 to 12.0, more preferably from 5.0 to 11.0, and from 6.0 to 10.0. More preferably, it is as follows. A known acid or base can be used to adjust the pH of the composition. Examples of such acids and bases include acids such as hydrochloric acid, nitric acid, and sulfuric acid; bases such as sodium hydroxide, potassium hydroxide, lithium hydroxide, triethylamine, and piperidine. Therefore, the aqueous binder composition may contain the above-described acid or base in addition to the above-described components in a range necessary for pH adjustment.

1.5. Method for Preparing Binder Composition for Electricity Storage Device Electrode The aqueous binder composition used in the present embodiment may be prepared by any method as long as it contains the above components. In order to prepare an aqueous binder composition, a method of adding the component (B) and other components added as needed to the polymerization mixture obtained by synthesizing the component (A); An appropriate method such as a method of dissolving the separated polymer in a liquid medium together with the component (B) and other components added as necessary can be employed. Of these, the former method is preferred because it is simple.

1.6. Storage Method for Storage Device Electrode Binder Composition The storage method for an electrical storage device electrode binder composition according to this embodiment (hereinafter also simply referred to as “storage method”) is the storage device electrode binder with respect to the internal volume of the container. The ratio of the volume of the void portion excluding the volume occupied by the composition is 1 to 20%, and the composition is stored at a temperature of 0 ° C. or higher and 30 ° C. or lower. The storage method according to the present embodiment includes (A) at least one polymer selected from the group consisting of a polyamic acid, a polyamic acid derivative, and an imidized polymer thereof, and water prepared by the method described above. Can be suitably used for a binder composition for an electricity storage device electrode.

  In the storage method according to this embodiment, the ratio of the volume of the void portion excluding the volume occupied by the aqueous binder composition to the internal volume of the container (%) in the container filled and stored with the above aqueous binder composition (%) ( Hereinafter, it is essential that the porosity is also 1 to 20%, preferably 3 to 15%, more preferably 5 to 10%. When the porosity exceeds the above range, the volatilization of moisture when the storage temperature changes increases, and foreign substances are formed by drying the water-based binder composition at the gas-liquid interface and the container wall surface. I can't. When the porosity is less than the above range, when the volume of the aqueous binder composition is changed due to a change in temperature, the container is deformed or the container is ruptured, so that it cannot be stably stored.

  In the storage method according to this embodiment, it is essential to store the above-mentioned aqueous binder composition at a temperature of 0 ° C. or higher and 40 ° C. or lower, preferably 3 ° C. or higher and 25 ° C. or lower. If the storage temperature exceeds the above range, the container tends to expand due to the volatilization of water during long-term storage, and foreign substances tend to be generated at the gas-liquid interface and the container wall surface. Can not. Moreover, since the hydrolysis of the imidized polymer in which a part of the polyamic acid and / or the polyamic acid derivative is imidized is remarkably accelerated at a temperature exceeding the above range, viscosity abnormality and aggregation of the component (A) occur. It tends to occur and cannot be stored stably.

  In the storage method according to the present embodiment, it is preferable that the container for storing the aqueous binder composition is a light-shielding container. In addition, even if it uses the storage container which permeate | transmits light, even if they are stored in the light-shielded space, it is considered that it is light-shielded. By storing it in a light-shielding container, the component (A) in the aqueous binder composition is stabilized and can be stored without deterioration in performance over a long period of time.

  The material of such a light-shielding container is not particularly limited as long as it is made of a material such as glass, metal, resin, etc. For example, a commercially available clean bottle, Ito can, sample bottle Etc. can be preferably used.

  Further, the shape and size of the container for storing the aqueous binder composition is not particularly limited, and containers of various shapes and sizes can be used.

In the storage method according to the present embodiment, the electrical conductivity of water used in the aqueous binder composition is preferably 1000 μS / cm or less, more preferably 500 μS / cm or less, and particularly preferably 100 μS / cm. It is as follows. As described above, the value of the electrical conductivity of water can be used as an indicator of the residual amount of metal ions in the aqueous binder composition. When metal ions remain in the aqueous binder composition, foreign substances are likely to be formed due to changes in the interaction strength of the component (A) due to cation exchange and gelation due to the development of a pseudo-crosslinked structure. The electrode mixture layer produced using the binder composition containing the foreign matter thus generated has a non-uniform structure, and the electricity storage device produced using this has a short circuit due to local excessive resistance or ignition. May cause.

  In the storage method according to the present embodiment, it is preferable that the oxygen concentration in the void portion atmosphere is 1% or less. When the oxygen concentration of the void atmosphere is within the above range, the binder component does not oxidize or change during long-term storage, and the precipitation and aggregation of the component (A) can be suppressed, and the generation of foreign matters. Can be effectively suppressed, and a significant change in appearance can be suppressed.

  According to the storage method according to this embodiment, the quality of the aqueous binder composition hardly changes during storage even when the storage period is 6 months, preferably 12 months, and more preferably 18 months. Moreover, a gel-like thing is not produced. For this reason, the same electrode mixture layer can be formed on the same conditions as forming an electrode mixture layer using the aqueous binder composition immediately after manufacture. Moreover, the effect which can improve the productivity of an aqueous binder composition becomes so large that a storage period becomes long in June, December, and 18 months.

2. Storage Device Electrode Slurry A storage device electrode slurry (hereinafter also simply referred to as “slurry”) can be produced using the above-described binder composition for an storage device electrode. The slurry for an electricity storage device electrode refers to a dispersion used for forming an electrode mixture layer on the surface of a current collector. Such a slurry contains at least the aqueous binder composition and the active material. Hereinafter, the components contained in the slurry will be described. The aqueous binder composition contained in the slurry is as described above.

2.1. The active material contained in the slurry is not particularly limited. For example, carbon materials, oxides containing lithium atoms, active materials containing silicon atoms, active materials containing titanium, lead compounds, tin compounds, arsenic compounds, antimony A compound, an aluminum compound, etc. can be mentioned.

  Examples of the carbon material include amorphous carbon, graphite, natural graphite, mesocarbon microbeads (MCMB), and pitch-based carbon fibers.

Examples of the oxide containing a lithium atom include lithium cobaltate, lithium nickelate, lithium manganate, ternary nickel cobalt lithium manganate, LiFePO ₄ , LiCoPO ₄ , LiMnPO ₄ , Li _0.90 Ti _0.05 Nb. _0.05 Fe _0.30 Co _0.30 Mn _0.30 PO _{4 and the} like.

Examples of the active material containing silicon atoms include silicon simple substance, silicon oxide, silicon alloy and the like, and silicon materials described in JP-A No. 2004-185810 can be used. The silicon oxide is preferably a silicon oxide represented by the composition formula SiOx (0 <x <2, preferably 0.1 ≦ x ≦ 1). The silicon alloy is preferably an alloy of silicon and at least one transition metal selected from the group consisting of titanium, zirconium, nickel, copper, iron and molybdenum. These transition metal silicides are preferably used because they have high electronic conductivity and high strength. Moreover, since the transition metal existing on the surface of the active material is oxidized and becomes an oxide having a hydroxyl group on the surface when the active material contains these transition metals, the binding force with the binder is also improved. preferable. As the silicon alloy, it is more preferable to use a silicon-nickel alloy or a silicon-titanium alloy, and it is particularly preferable to use a silicon-titanium alloy. The silicon content in the silicon alloy is preferably 10 mol% or more, and more preferably 20 to 70 mol%, based on all the metal elements in the alloy. The active material containing a silicon atom may be single crystal, polycrystalline, or amorphous.

  When the slurry is used for producing a negative electrode for an electricity storage device, the negative electrode active material contained in the slurry preferably contains an active material containing silicon atoms. Since silicon atoms have a larger amount of occlusion of lithium per unit weight than other active material groups, the active material contains an active material containing silicon atoms, thereby increasing the storage capacity of the resulting power storage device. As a result, the output and energy density of the electricity storage device can be increased. The negative electrode active material is more preferably composed of a mixture of an active material containing silicon atoms and a carbon material. Since the volume change due to charging and discharging is small, the use of a mixture of an active material containing a silicon atom and a carbon material as a negative electrode active material alleviates the effect of the volume change of the active material containing a silicon atom. The adhesion between the electrode mixture layer and the current collector can be further improved. The negative electrode active material is particularly preferably composed of a mixture of an active material containing silicon atoms and graphite.

  The proportion of the active material containing silicon atoms in 100% by mass of the active material is preferably 1% by mass or more, more preferably 1 to 50% by mass, and further preferably 5 to 45% by mass. The content is preferably 10 to 40% by mass.

  The shape of the active material is preferably granular. The particle size (average median particle size) of the particles is preferably 0.1 to 100 μm, and more preferably 1 to 20 μm.

  The use ratio of the active material is preferably such that the content of the component (A) in the aqueous binder composition is 0.1 to 25 parts by mass with respect to 100 parts by mass of the active material. It is more preferable to set it as the ratio used as -15 mass parts. By setting it as such a usage rate, it is possible to produce an electrode that is excellent in adhesiveness and has low electrode resistance and excellent charge / discharge characteristics.

2.2. Other components The slurry may contain other components as necessary in addition to the aqueous binder composition and the active material. Examples of other components include a conductivity-imparting agent and a thickener.

2.2.1. Conductivity-imparting agent Specific examples of the conductivity-imparting agent include carbon in a lithium ion secondary battery. Examples of carbon include activated carbon, acetylene black, ketjen black, furnace black, graphite, carbon fiber, and fullerene. Among these, acetylene black or ketjen 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.

2.2.2. Thickener The slurry may contain a thickener from the viewpoint of improving its coatability. Specific examples of the thickener include, for example, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose and other cellulose derivatives; ammonium salts or alkali metal salts of the above cellulose derivatives; poly (meth) acrylic acid, Polycarboxylic acids such as modified poly (meth) acrylic acid; alkali metal salts of the above polycarboxylic acids; polyvinyl alcohol (co) polymers such as polyvinyl alcohol, modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer; (meth) Unsaturated carboxylic acids such as acrylic acid, maleic acid and fumaric acid;
Water-soluble polymers such as saponified products of copolymers with vinyl esters can be mentioned. The use ratio of the thickener is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the active material.

2.3. Method for Producing Slurry for Electricity Storage Device Electrode The slurry may be produced by any method as long as it contains the aqueous binder composition and the active material. From the viewpoint of producing a slurry having better dispersibility and stability more efficiently and inexpensively, an active material and optional additive components used as needed are added to the aqueous binder composition and mixed. It is preferable to manufacture by doing.

  In order to mix an aqueous binder composition, an active material, and another component, it can carry out by stirring by a well-known method. As mixing and stirring for producing the slurry, it is necessary to select a mixer that can stir to such an extent that no agglomerates of the active material remain in the slurry and sufficient dispersion conditions as necessary. The degree of dispersion can be measured by a particle gauge, but it is preferable to mix and disperse so that aggregates larger than at least 100 μm are eliminated. Examples of the mixer that meets such conditions include a ball mill, a bead mill, a sand mill, a defoamer, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, and a Hobart mixer. it can.

The preparation of the slurry (mixing operation of each component) is preferably performed at least part of the process under reduced pressure. Thereby, it can prevent that a bubble arises in the electrode mixture layer obtained. The degree of pressure reduction is preferably about 5.0 × 10 ^{3 to} 5.0 × 10 ⁵ Pa as an absolute pressure.

3. Electric storage device electrode An electric storage device electrode (hereinafter, also simply referred to as “electrode”) includes a current collector and an electrode mixture layer formed on the surface of the current collector using the slurry for an electric storage device electrode. . As a specific production example, a coating film is formed on the surface of an appropriate current collector such as a metal foil by applying the slurry produced using the aqueous binder composition described above, and then a liquid is formed from the coating film. By removing the medium by drying, an electrode mixture layer is formed on the surface of the current collector. Thus, the electrical storage device electrode by which the electrode mixture layer was formed in the surface of an electrical power collector can be manufactured.

  The electrode produced in this manner is bonded to the surface of the current collector with an electrode mixture layer containing the above-described component (A) and the active material, and optional additional components used as necessary. It will be. Therefore, such an electricity storage device electrode has a large charge / discharge capacity, and the degree of deterioration of the charge / discharge capacity when the charge / discharge cycle is repeated is small.

3.1. Current collector The current collector is not particularly limited as long as it is made of a conductive material. In a lithium ion secondary battery, a current collector made of metal such as iron, copper, aluminum, nickel, and stainless steel is used. In particular, when aluminum is used for the positive electrode and copper is used for the negative electrode, the effect of the slurry described above. Appears most often. As the current collector in the nickel metal hydride secondary battery, a punching metal, an expanded metal, a wire mesh, a foam metal, a mesh metal fiber sintered body, a metal plated resin plate, or the like is used.

  The shape and thickness of the current collector are not particularly limited. The thickness of the current collector is preferably 1 to 500 μm, more preferably 5 to 150 μm, and particularly preferably 10 to 50 μm. As the shape of the current collector, a sheet shape is preferably used.

3.2. Method for producing electricity storage device electrode An example of a method for producing the electricity storage device electrode is shown below. First, a slurry containing the aqueous binder composition and the active material is applied to the surface of the current collector to form a coating film, and then the coating film is heated as necessary to form a liquid medium. By drying and removing the electrode mixture layer, an electrode mixture layer is formed on the surface of the current collector. Thus, the electrical storage device electrode by which the electrode mixture layer was formed in the surface of an electrical power collector can be manufactured.

  There is no particular limitation on the method for applying the slurry to the current collector. The coating can be performed by an appropriate method such as a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a dipping method, or a brush coating method. The amount of slurry applied is not particularly limited, but the thickness of the electrode mixture layer formed after removing the liquid medium is preferably 5 to 250 μm, and preferably 20 to 100 μm. More preferred.

  The method for removing the liquid medium from the coated film after coating is not particularly limited, and may be, for example, drying with hot air, hot air, low-humidity air; vacuum drying; (far) drying by irradiation with infrared rays, electron beams, or the like. . The drying speed is appropriately set so that the liquid medium can be removed as quickly as possible within a speed range in which the electrode mixture layer does not crack due to stress concentration or the electrode mixture layer does not peel from the current collector. Can be set.

  Furthermore, it is preferable to increase the density of the electrode mixture layer by pressing the electrode mixture layer after removing the liquid medium. Examples of the pressing method include a mold press and a roll press. The press conditions should be set appropriately depending on the type of press equipment used and the desired value of the density of the electrode mixture layer. This condition can be easily set by a few preliminary experiments by those skilled in the art. For example, in the case of a roll press, either the gap type or the pressure type may be used, and the linear pressure is 0.1 to 10 t / cm, Preferably, at a pressure of 0.5 to 5 t / cm, for example, at a roll temperature of 20 to 100 ° C., the coating speed (roll rotational speed) after removal of the liquid medium is 1 to 80 m / min, preferably 5 to 5 m / min. It can be carried out at 50 m / min.

Density of the electrode mixture layer after pressing, when using electrodes as the positive electrode is preferably in a 1.5~2.4g / cm ^3, be 1.7~2.2g / cm ³ it is more preferable; when using an electrode as a negative electrode is preferably in a 1.2~1.9g / cm ^3, and more preferably to 1.3~1.8g / cm ^3.

  It is preferable that the pressed coating film is further heated under reduced pressure to completely remove the liquid medium. In this case, the degree of reduced pressure is preferably 50 to 200 Pa, more preferably 75 to 150 Pa as an absolute pressure. The heating temperature is preferably a temperature range in which the polyamic acid structure in the coating film is not thermally imidized, preferably 100 to 300 ° C, and more preferably 150 to 200 ° C. The heating time is preferably 2 to 12 hours, and more preferably 4 to 8 hours.

In any process for forming the electrode mixture layer on the surface of the current collector using the slurry, the process temperature preferably does not exceed 200 ° C, and more preferably does not exceed 180 ° C. Here, the steps for forming the electrode mixture layer include the slurry application step, the liquid medium removal step from the coating film, an optional pressing step, a heating step under reduced pressure, a pressing step, and the like. About all the steps that those skilled in the art perform to form an electrode mixture layer. The above process temperature refers to the temperature of the slurry, the current collector or the electrode mixture layer itself, the temperature of the surrounding atmosphere surrounding them, and the temperature of the device or instrument in contact with or close to them. The electricity storage device electrode manufactured in this way has a large charge / discharge capacity, and the degree of deterioration of the charge / discharge capacity when the charge / discharge cycle is repeated is small.

4). Power storage device A power storage device includes the above power storage device electrode. Such an electricity storage device includes the above electricity storage device electrode, and further contains an electrolytic solution, and can be manufactured according to a conventional method using components such as a separator. As a specific manufacturing method, for example, a negative electrode and a positive electrode are overlapped via a separator, and this is wound or folded according to the shape of the battery, and stored in a battery container, and an electrolytic solution is injected into the battery container. Can be mentioned. The shape of the battery can be an appropriate shape such as a coin shape, a cylindrical shape, a square shape, or a laminate shape.

  The electrolyte solution may be liquid or gel, and an electrolyte that effectively expresses the function as a battery may be selected from the known electrolytes used for the electricity storage device according to the type of the active material. The electrolytic solution can be a solution in which an electrolyte is dissolved in a suitable solvent.

As the electrolyte, for example, in the lithium ion secondary battery, any conventionally known lithium salt can be used, and specific examples thereof include, for example, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ CO _2. , LiAsF ₆ , LiSbF ₆ , LiB ₁₀ Cl ₁₀ , LiAlCl ₄ , LiCl, LiBr, LiB (C ₂ H ₅ ) ₄ , LiCF ₃ SO ₃ , LiCH ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂₎ 2 _N, and the like can be exemplified lower aliphatic lithium carboxylate.

  The solvent for dissolving the electrolyte is not particularly limited, and specific examples thereof include carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and fluoroethylene carbonate. Compounds; lactone compounds such as γ-butyrolactone; ether compounds such as trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran; sulfoxide compounds such as dimethyl sulfoxide One or more selected from these can be used.

  The concentration of the electrolyte in the electrolytic solution is preferably 0.5 to 3.0 mol / L, more preferably 0.7 to 2.0 mol / L.

5. EXAMPLES Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. “Part” and “%” in Examples and Comparative Examples are based on mass unless otherwise specified.

5.1. Synthesis of polyamic acid and polyamic acid derivative <Synthesis Example 1>
The inside of the 3 L flask equipped with a stirrer, a thermometer and a condenser was heated with a heat gun in a reduced pressure state to remove residual moisture inside the container, and then filled with dry nitrogen gas. Into this flask, 1,166 g of N-methyl-2-pyrrolidone (NMP) subjected to dehydration by a dehydration distillation method using calcium hydride as a solvent in advance, and 3,3 ′, 4, as tetracarboxylic dianhydride 80.556 g (250.0 mmol) of 4′-benzophenonetetracarboxylic dianhydride and 50.59 g (250.0 mmol) of 4,4′-diaminodiphenyl ether as diamine were charged and reacted at 25 ° C. with stirring for 3 hours. To obtain a polymer solution containing 10% by mass of polyamic acid. With respect to this polymer solution, 28.053 g (500. KOH) of 2 equivalents of tetracarboxylic dianhydride used.
0 mmol), a polymer salt (polyamic acid derivative P1) was precipitated. The precipitate was filtered and dried, and dissolved in ion-exchanged water so that the polyamic acid derivative P1 was 10% by mass, thereby obtaining an aqueous solution of the polyamic acid derivative P1.

<Synthesis Examples 2-4>
10% by mass of each of polyamic acid derivatives P2 to P4 in the same manner as in Synthesis Example 1 except that the types and amounts of use of tetracarboxylic dianhydride and diamine were as shown in Table 1, respectively. A polymer solution containing was obtained. The solution viscosities of these polymer solutions are also shown in Table 1.

<Synthesis Example 5>
In the same manner as in Synthesis Example 1, a polymer solution containing 10% by mass of polyamic acid was obtained according to the composition shown in Table 2. To this polymer solution, 0.2 g (1.548 mol) of isoquinoline and 60 mL of toluene are added, the temperature of the solution is raised to 180 ° C., and reaction is performed while removing by-product water, and an imidized polymer of polyamic acid. Solution was obtained. After allowing to cool, 28.053 g (500.0 mmol) of KOH was added to precipitate a polymer salt (imidized polymer P5 of polyamic acid derivative). The precipitate was filtered and dried, and dissolved with ion-exchanged water so that the imidized polymer P5 of the polyamic acid derivative was 10% by mass, thereby obtaining an aqueous solution of the imidized polymer P5 of the polyamic acid derivative. When the imidization ratio of the imidized polymer P5 of the polyamic acid derivative was determined by ¹ H-NMR measurement, it was 95%.

The abbreviations of the components in Table 1 have the following meanings. In addition, “-” in Table 1 above indicates that the corresponding component is not contained.
<Tetracarboxylic dianhydride>
BTDA: 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride PMDA: 1,2,4,5-benzenetetracarboxylic dianhydride TDA: 4- (2,5-dioxo Tetrahydrofuran-3-yl) -1,2,3,4-tetrahydronaphthalene-1,2-carboxylic anhydride <diamine>
DDE: 4,4′-diaminodiphenyl ether DDM: 4,4′-diaminodiphenylmethane

5.2. Synthesis of Active Material A mixture of pulverized silicon dioxide powder (average particle size 10 μm) and carbon powder (average particle size 35 μm) was subjected to nitrogen in an electric furnace adjusted to a temperature in the range of 1,100 to 1,600 ° C. Under an air stream (0.5 NL / min), heat treatment for 10 hours is performed, and the composition formula SiOx (x = 0.5 to 1.1)
A silicon oxide powder represented by the formula (average particle size 8 μm) was obtained. 300 g of this silicon oxide powder was charged into a batch-type heating furnace, and the temperature was increased from room temperature (25 ° C.) to 1,100 ° C. at a temperature increase rate of 300 ° C./h while maintaining a reduced pressure of 100 Pa with a vacuum pump. Warm up. Next, while maintaining the pressure in the heating furnace at 2,000 Pa, heat treatment (graphite coating treatment) was performed at 1,100 ° C. for 5 hours while introducing methane gas at a flow rate of 0.5 NL / min. After the completion of the graphite coating treatment, the powder was cooled to room temperature at a temperature decrease rate of 50 ° C./h to obtain about 330 g of graphite-coated silicon oxide powder. This graphite-coated silicon oxide is a conductive powder (active material) whose surface is coated with graphite, and has an average particle diameter of 10.5 μm. The ratio of the graphite film in the case of mass% was 2 mass%.

5.3. Example 1
(1) Preparation of Binder Composition for Electricity Storage Device Electrode 100 g of polymer aqueous solution containing polyamic acid derivative P1 obtained in Synthesis Example 1 (containing 10 g of polyamic acid derivative P1) in an Ar-substituted glove box. In contrast, N-methylpyrrolidone (NMP) and 1,2-benzisothiazolin-3-one (C1) are added using a microsyringe so as to have the content ratio shown in Table 2, thereby A binder composition was prepared.

(2) Storage test of the binder composition for an electricity storage device electrode The binder composition for an electricity storage device electrode prepared as described above is put in a storage container, and the ratio (void ratio) to the internal volume of the container, the storage temperature, and the presence or absence of light shielding The conditions were as described in 2 and stored for 6 months. The change in viscosity of the binder composition for an electricity storage device electrode after 6 months storage was measured using a B-type viscometer, and a change in excess of ± 5% with respect to the viscosity before storage was judged as a viscosity abnormality. Regarding the presence or absence of foreign matter in the binder composition for an electricity storage device electrode after storage for 6 months, the case where some of the stored sample was filtered after passing through a 200-mesh filter was indicated as x, otherwise it was indicated as ◯. Moreover, it is shown in Table 2 as x when the sample is clearly colored as compared with the sample before storage, and when there is no visual difference.

  In the case of light shielding, a clean barrier (registered trademark) bottle commercially available from Aicello Chemical Co., Ltd. was used as a light shielding storage container. Moreover, when storing without light-shielding, it stored under fluorescent lamp irradiation using the PYREX (trademark) wide-mouthed medium bottle.

(3) Preparation of slurry for electricity storage device electrode Graphite (Hitachi, Ltd.) having an average particle diameter of 22 μm as a negative electrode active material in a biaxial planetary mixer (trade name “TK Hibismix 2P-03” manufactured by PRIMIX Co., Ltd.) 80 parts by mass (in terms of solid content) manufactured by Kasei Kogyo Co., Ltd., 20 parts by mass of the graphite-coated silicon oxide synthesized above, and acetylene black (Electrochemical Industry Co., Ltd.) as a conductive agent 1 part by mass was added and mixed at 20 rpm for 3 minutes. Next, 100 parts by mass and 20 parts by mass of water were added to the binder composition after further storing for 6 months as described above, and the mixture was stirred at 60 rpm for 1 hour. Then, using a stirring deaerator (trade name “ARV930-TWIN”, manufactured by Shinkey Co., Ltd.), a slurry was prepared by stirring and mixing at 600 rpm for 5 minutes under a reduced pressure of 25 kPa absolute pressure.

(4) Production of electricity storage device electrode The slurry prepared above is applied to the surface of a current collector made of copper foil having a thickness of 10 μm so that the mass of the electrode mixture layer after solvent removal is 4.50 mg / cm ^2. The film thickness was adjusted and applied uniformly by the doctor blade method, and dried at 120 ° C. for 5 minutes to form a coating film. Subsequently, the roll temperature was adjusted to 30 ° C., the linear pressure was set to 1 t / cm, and the feed rate was set to 0.5 m / second using a gap-pressing roll press machine (trade name “SA-601” manufactured by Tester Sangyo Co., Ltd.) And the electrode mixture layer was adjusted so that the density of the electrode mixture layer was 1.60 g / cm ³ . Furthermore, it heated at 160 degreeC under pressure reduction of absolute pressure 100Pa for 6 hours, and the electrical storage device electrode (negative electrode) was obtained by forming an electrode mixture layer.

(5) Production of electricity storage device In the glove box substituted with argon so that the dew point is −80 ° C. or lower, the negative electrode produced above is punched and formed to a diameter of 15.5 mm, with the electrode mixture layer facing upward. It was placed on a bipolar coin cell (trade name “HS flat cell” manufactured by Hosen Co., Ltd.). Next, a separator (made by Celgard Co., Ltd., trade name “Celgard # 2400”) made of a polypropylene porous film punched to a diameter of 24 mm is placed on the above negative electrode, and the electrolyte solution is placed so that air does not enter. After injecting 500 μL, a 200 μm-thick lithium foil punched out to a diameter of 16.6 mm is placed as a counter electrode (positive electrode), and the outer body of the bipolar coin cell is closed with a screw and sealed. A lithium ion battery 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 solvent of ethylene carbonate / ethyl methyl carbonate = 1/1 (mass ratio). The power storage device thus obtained was subjected to “(6) Evaluation of power storage device”.

(6) Evaluation of electricity storage device <Charge / discharge cycle characteristics>
About the electrical storage device manufactured above, charging is started at a constant current (0.2 C), and when the voltage reaches 0.01 V, charging is continued at a constant voltage (0.01 V). The time point when the temperature reached 0.05 C was determined to be charging completion (cut-off). Next, discharging was started at a constant current (0.2 C), and when the voltage reached 2.0 V, the discharge was completed (cutoff), and the initial charge / discharge was completed. Next, 0.5 C charge / discharge was performed as follows for the above-described electricity storage device that was charged and discharged for the first time.

First, charging was started at a constant current (0.5 C). When the voltage reached 0.01 V, charging was continued at a constant voltage (0.01 V), and the current value became 0.05 C. The time point was regarded as charging completion (cut-off). Next, discharge was started at a constant current (0.2 C), and when the voltage reached 2.0 V, the discharge was completed (cutoff), and the discharge capacity at 0.5 C (0.5 C discharge capacity in the first cycle) = A) was measured. The charge / discharge of 0.5C was repeated, and the capacity maintenance rate after 100 cycles was calculated by the following formula (3), where B was the 0.5C discharge capacity at the 100th cycle.
Capacity maintenance rate (%) = (B / A) × 100 (3)
The evaluation results are also shown in Table 2. If the capacity retention rate after 100 cycles is 90% or more and less than 95%, it can be determined that the charge / discharge cycle characteristics are excellent, and if it is 95% or more, the charge / discharge cycle characteristics are extremely excellent. Can be determined. If the value of the capacity maintenance rate after 100 cycles is less than 90%, it can be determined that it is defective.

5.4. Examples 2-8 and Comparative Examples 1-8
In the said Example 1, 10 mass% polymer aqueous solution obtained in any of the said synthesis examples 1-5 was used so that it might become a kind of Table 2-Table 3 as (A) component, (B) component And the binder composition for electrical storage device electrodes was prepared in the same manner as in Example 1 except that the types and content ratios of the components (C) were as described in Tables 2 to 3, and Tables 2 to 3 were prepared. The product was stored for 6 months under the conditions described in. Using each of these stored aqueous binder compositions, a slurry for an electricity storage device electrode was prepared in the same manner as in Example 1, and an electricity storage device electrode and an electricity storage device were produced and evaluated. These evaluation results are also shown in Tables 2 to 3.

5.5. Evaluation results Tables 2 to 3 below show the evaluation results of the examples and comparative examples.

The abbreviations or symbols of each component in Tables 2 to 3 represent the following compounds, respectively. Moreover, "-" in Tables 2 to 3 indicates that the corresponding component is not contained.
<(B) component>
NMP: N-methylpyrrolidone NEP: N-ethylpyrrolidone GBL: γ-butyrolactone DMF: dimethylformamide THF: tetrahydrofuran EGMBE: ethylene glycol monobutyl ether PEGMEA: propylene glycol-1-monomethyl ether-2-acetate <(C) component>
C1: 1,2-benzisothiazolin-3-one C2: 2-methyl-4-isothiazolin-3-one C3: Nn-butyl-1,2-benzisothiazolin-3-one C4: 5 -Chloro-2-methyl-4-isothiazolin-3-one

  According to the results in Tables 2 to 3, it was revealed that the method for storing the binder composition for an electricity storage device electrode according to the present invention is effective.

  The present invention is not limited to the above embodiment, and various modifications can be made. The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). The present invention also includes a configuration in which a non-essential part of the configuration described in the above embodiment is replaced with another configuration. Furthermore, the present invention includes a configuration that achieves the same effects as the configuration described in the above embodiment or a configuration that can achieve the same object. Furthermore, the present invention includes a configuration obtained by adding a known technique to the configuration described in the above embodiment.

Claims (9)

(A) A light-shielding container is filled with a binder composition for an electricity storage device electrode containing at least one polymer selected from the group consisting of polyamic acid, polyamic acid derivatives, and imidized polymers thereof, and water. And store it,
The ratio of the volume of the void portion excluding the volume occupied by the binder composition for an electricity storage device electrode to the internal volume of the light-shielding container is 1 to 20%, and is stored at a temperature of 0 ° C. or higher and 40 ° C. or lower. The storage method of the binder composition for electrical storage device electrodes. The electric storage pH of the device electrode binder composition is 5 to 11, storage method of the electric storage device electrode binder composition of claim 1. The storage method of the binder composition for electrical storage device electrodes of Claim 1 or Claim 2 whose electrical conductivity of the said water is 1,000 microsiemens / cm or less. The binder composition for an electricity storage device electrode further comprises (B) N-methylpyrrolidone, N-ethylpyrrolidone, γ-butyrolactone, N, N-dimethylacetamide, butyrocellosolve, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, 2. It contains at least one compound selected from the group consisting of propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, propylene glycol-1-monomethyl ether-2-acetate, aliphatic ether and aliphatic alcohol. storage method of a power storage device electrode binder composition of any one of claims 3. In the binder composition for an electricity storage device electrode, when the content of the polymer (A) is Ma parts by mass and the content of the compound (B) is Mb parts by mass, the ratio Ma / Mb between them is 50 to 50 parts. The storage method of the binder composition for electrical storage device electrodes of Claim 4 which is 5,000. (A) at least one polymer selected from the group consisting of polyamic acid, polyamic acid derivatives, and imidized polymers thereof; (B) N-methylpyrrolidone, N-ethylpyrrolidone, γ-butyrolactone, N , N-dimethylacetamide, butyrocellosolve, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, propylene glycol-1-monomethyl ether-2-acetate, aliphatic ether and aliphatic alcohol When containing at least one compound selected from the group consisting of water and water, the content of the (A) polymer is Ma parts by mass, and the content of the (B) compound is Mb parts by mass The ratio Ma / Mb of both is Which is a 0 to 5,000 storage device electrode binder composition to a method storing and filled into a container,
The ratio of the volume of the void portion excluding the volume occupied by the binder composition for an electricity storage device electrode with respect to the internal volume of the container is 1 to 20%, and is stored at a temperature of 0 ° C. or more and 40 ° C. or less, The storage method of the binder composition for electrical storage device electrodes. The storage method of the binder composition for electrical storage device electrodes according to claim 6, wherein the binder composition for electrical storage device electrodes has a pH of 5 to 11. The storage method of the binder composition for an electrical storage device electrode according to claim 6 or 7, wherein the electrical conductivity of the water is 1,000 µS / cm or less. The binder composition for an electricity storage device electrode further contains (C) an isothiazoline compound, and the concentration of the (C) isothiazoline compound in the binder composition is 15 ppm or more and 500 ppm or less. The storage method of the binder composition for electrical storage device electrodes as described in any one of claim | item 8 .