JP6052528B1 - Slurry for lithium ion secondary battery negative electrode, lithium ion secondary battery negative electrode and lithium ion secondary battery - Google Patents

Abstract

Provided is a binder composition for an electricity storage device electrode which provides an electricity storage device having a large charge / discharge capacity and a small capacity deterioration due to repeated charge / discharge cycles even when an active material containing a silicon atom is contained. The power storage device electrode binder composition according to the present invention comprises (A) at least one polymer selected from the group consisting of polyamic acid, polyamic acid derivatives, and imidized polymers thereof; B) at least one compound selected from the group consisting of aliphatic ethers and aliphatic alcohols. [Selection figure] None

Description

  The present invention relates to a binder composition for an electricity storage device electrode, a slurry for an electricity storage device electrode, an electricity storage device electrode, and an electricity storage device.

  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 an electrode 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 can be mentioned powder-off resistance, etc., 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 “active material 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 occlude and release lithium by forming an intermetallic compound with lithium. 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 conventional electrode binder is applied to the silicon material, the initial adhesion cannot be maintained, and a significant capacity reduction occurs due to charging / discharging. .

  A method of using polyimide as an electrode binder for holding such a silicon material in an active material layer has been proposed (see, for example, Patent Documents 1 to 3). 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 1 to 3, by applying a slurry for an 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.

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

  However, since the binder using the polyimide disclosed in Patent Documents 1 to 3 described above has insufficient adhesion, the electrode deteriorates due to repeated charge / discharge cycles, and sufficient durability cannot be obtained. was there.

  Therefore, some embodiments according to the present invention provide a power storage device electrode that provides a power storage device having a large charge / discharge capacity and a small capacity deterioration due to repeated charge / discharge cycles even when an active material containing silicon atoms is included. A binder composition is provided.

  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 binder composition for an electricity storage device electrode according to the present invention is:
(A) at least one polymer selected from the group consisting of a polyamic acid, a polyamic acid derivative, and an imidized polymer thereof;
(B) at least one compound selected from the group consisting of aliphatic ethers and aliphatic alcohols;
It is characterized by containing.

[Application Example 2]
In the binder composition for an electricity storage device electrode of Application Example 1,
When the content of the component (B) is Mb parts by mass and the content of the component (A) is Ma parts by mass, the value of Mb / Ma can be 0.00001 to 1.

[Application Example 3]
One aspect of the slurry for the electricity storage device electrode according to the present invention is:
It contains the binder composition for electrical storage device electrodes of the application example 1 or the application example 2, and an active material.

[Application Example 4]
In the slurry for the electricity storage device electrode of Application Example 3,
The active material may include an active material containing a silicon atom.

[Application Example 5]
One aspect of the electricity storage device electrode according to the present invention is:
It includes a current collector and an active material layer formed on the surface of the current collector using the slurry for an electricity storage device electrode of Application Example 3 or Application Example 4.

[Application Example 6]
One aspect of the electricity storage device according to the present invention is:
The power storage device electrode of Application Example 5 is included.

  According to the binder composition for an electricity storage device electrode according to the present invention, an electricity storage device having a large charge / discharge capacity and a small capacity deterioration due to repeated charge / discharge cycles is produced even when an active material containing a silicon atom is contained. be able to.

  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.

1. Binder composition for an electricity storage device electrode The binder composition for an electricity storage device electrode according to the present embodiment (hereinafter also simply referred to as “binder composition”) includes (A) a polyamic acid, a polyamic acid derivative, and an imidized weight thereof. And at least one polymer selected from the group consisting of (B) aliphatic ethers and aliphatic alcohols, and at least one polymer selected from the group consisting of coalesced (hereinafter also referred to simply as “component (A)”). (Hereinafter also simply referred to as “component (B)”). The binder composition according to the present embodiment is a material for producing an electricity storage device electrode (active material layer) having improved binding ability between active materials, adhesion ability between an active material and a current collector, and powder fall resistance. Can be used. Hereinafter, each component contained in the binder composition according to the present embodiment will be described in detail.

1.1. (A) Component The binder composition according to 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. The component (A) has a function as a binder for improving the binding ability between the active materials, the adhesion ability between the active material and the current collector, and the powder fall resistance in the active material layer constituting the power 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 binder composition according to this embodiment is imidized, the imidization ratio of the polyamic acid and / or polyamic acid derivative is particularly limited However, 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 binder composition within the above range, the stability of the slurry for an electricity storage device electrode prepared using the binder composition is improved. It is preferable because an electricity storage device electrode having excellent adhesion and charge / discharge characteristics can be produced.

  In addition, when the binder composition which concerns on this embodiment contains the imidation polymer of a polyamic acid and / or a polyamic acid derivative, it is preferable that an imidation rate is 80% or more, and it is more preferable that it is 85% or more. It is preferably 90% or more. 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, if the imidization ratio of the imidized polymer is in the above preferred range, the polyamic acid and / or polyamic acid and its 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.

  A polyamic acid can be obtained by reacting a tetracarboxylic dianhydride and a diamine. A polyamic acid ester which is one type of polyamic acid derivative 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 can be obtained by imidization by subjecting a part of the amic acid structure of the polyamic acid and / or polyamic acid derivative to dehydration ring closure using a catalyst or a catalyst. it can.

  Examples of tetracarboxylic dianhydrides used to synthesize polyamic acids or polyamic acid derivatives include aliphatic tetracarboxylic dianhydrides, alicyclic tetracarboxylic dianhydrides, and aromatic tetracarboxylic dianhydrides. And so on. 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 Dianhydride, 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 tetracarboxylic dianhydride, 3,3′4,4′-diphenylsulfone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′ , 4'-biphenyltetracarbo Acid dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride and the like can be mentioned, respectively, and tetracarboxylic dianhydride described in JP 2010-97188 A is used. be able to.

  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 the polyamic acid derivative include an aliphatic diamine, an alicyclic diamine, an aromatic diamine, and a 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] hexafluoropropane, 2,2-bis (4-amino Phenyl) 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-diaminoacridine, 3,6-diaminocarbazole, N- Methyl-3,6-diaminocarbazole, N-ethyl-3,6-diaminocarbazole, N-phenyl-3,6-diaminocarbazole, N, N′-bis (4-aminophenyl) -benzidine, N, N ′ -Bis (4-aminophenyl) -N, N'-dimethylbenzidine, 1,4-bis- (4-aminophenyl) -pi Perazine, 3,5-diaminobenzoic acid and the like; Examples of the diaminoorganosiloxane include 1,3-bis (3-aminopropyl) -tetramethyldisiloxane, respectively, and JP 2010-97188 A The diamine described in the publication can be used. The diamine used when synthesizing the polyamic acid or the polyamic acid derivative is preferably an aromatic diamine containing 30 mol% or more, more preferably 50 mol% or more, based on 100 mol% of the total diamine. 80 mol% or more is particularly preferable.

  When synthesizing a polyamic acid or polyamic acid derivative, 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 proportion of tetracarboxylic dianhydride and diamine used for the synthesis reaction of the 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, tertiary amines such as pyridine, collidine, lutidine, 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 150 ° C. The reaction time is preferably 1 to 10 hours, more preferably 2 to 5 hours.

  The component (A) obtained as described above preferably has a solution viscosity of 100 to 100,000 mPa · s, when it is made into an aqueous solution having a concentration of 10% by mass, and is preferably 500 to 50,000 mPa. More preferably, it has a solution viscosity of s. The solution viscosity (mPa · s) of the component (A) is a value measured at 25 ° C. using an E-type rotational viscometer for a 10% by mass solution prepared using ion-exchanged water.

  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. (B) Component The binder composition according to the present embodiment contains (B) at least one compound selected from the group consisting of aliphatic ethers and aliphatic alcohols. 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 according to the present embodiment is such that the content of the component (B) in the composition is Mb part by mass, and the content of the component (A) is Ma part by mass. The ratio Mb / Ma between the two is preferably 0.00001-1. The value of this ratio Mb / Ma is more preferably 0.0005 to 0.5, and particularly preferably 0.001 to 0.1. When the content ratio of the component (B) in the binder composition according to this embodiment is within the above range, the adhesion is improved and the electrical characteristics of the obtained electricity storage device electrode are improved. In particular, this effect is remarkable when an active material containing a silicon atom is used as the active material. Although the expression mechanism of this is not clear, the present inventors presume that it is caused by the following actions.

  That is, it is known that when initial charging / discharging is performed in a lithium ion secondary battery, a SEI (Solid Electrolyte Interface) film is formed on the active material. In the SEI film formation, when the component (A) is used as a binder and the component (B) coexists, the unshared electron pair on the oxygen atom has a high affinity for the Lewis-acid active material containing silicon atoms. Coordinate. As a result, an SEI film that is electrochemically stable under reducing conditions is formed, so that it is presumed that irreversible capacity is suppressed and good repeated charge / discharge characteristics are exhibited.

1.3. Liquid medium The liquid medium used in the binder composition according to this embodiment may be either an aqueous medium or a non-aqueous medium, but is preferably an aqueous medium, and more preferably water. The non-aqueous medium can be added to the aqueous medium at an arbitrary ratio. Specific examples of the non-aqueous medium include, for example, ketones such as acetone, methyl ethyl ketone, cyclopentanone, and isophorone; lactones such as γ-butyrolactone and δ-butyrolactone; lactams such as β-lactam; dimethylformamide, N-methylpyrrolidone, N A chain or cyclic amide compound such as N, dimethylacetamide; a compound having a nitrile group such as methylene cyanohydrin, ethylene cyanohydrin, 3,3′-thiodipropionitrile, acetonitrile; a glycol compound such as ethylene glycol or propylene glycol Diethylene glycol such as diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol ethyl butyl ether, or derivatives thereof, among these, One or more selected from can be used.

  The use ratio of the liquid medium in the binder composition according to the present embodiment is the solid content concentration of the binder composition (the ratio of the total mass of components other than the liquid medium in the composition to the total mass of the composition) It is preferable to set it as the ratio used as 5-70 mass%, and it is more preferable to set it as the ratio used as 10-55 mass%.

1.4. PH of binder composition for electricity storage device electrode
The pH of the binder composition according to this embodiment is preferably 5 to 9, and more preferably 6 to 7. 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 binder composition according to this embodiment may contain the above acid or base as other components in addition to the component (A) and the component (B) in a range necessary for pH adjustment.

1.5. Method for Preparing Binder Composition for Electricity Storage Device Electrode The binder composition according to this embodiment may be prepared by any method as long as it contains the above components. To prepare the binder composition according to this embodiment, a method of adding the component (B) and other components added as necessary to the polymerization mixture obtained by synthesizing the component (A); synthesizing the component (A) The polymer isolated from the polymerization mixture can be obtained by an appropriate method such as a method in which the polymer (B) and other components added as necessary are dissolved in a liquid medium. Of these, the former method is preferred because it is simple.

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 active material layer on the surface of a current collector. The slurry according to this embodiment contains at least the binder composition for an electricity storage device electrode and an active material. Hereinafter, the components contained in the slurry according to the present embodiment will be described. The binder composition for an electricity storage device electrode contained in the slurry according to the present embodiment is as described above.

2.1. Active material The active material contained in the slurry according to the present embodiment is not particularly limited, and for example, a carbon material, an oxide containing a lithium atom, an active material containing a silicon atom, an active material containing titanium, a lead compound, and a tin compound Arsenic compounds, antimony compounds, aluminum compounds, and the like.

  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 according to the present embodiment is used for producing a negative electrode of 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 an active material for a negative electrode alleviates the effect of the volume change of the active material containing a silicon atom. Thus, the adhesion between the active material 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 use ratio of the active material is preferably such that the content of the component (A) in the binder composition is 0.1 to 25 parts by mass with respect to 100 parts by mass of the active material. More preferably, the ratio is 15 parts by mass. 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 according to the present embodiment may contain other components as necessary in addition to the binder composition for an electricity storage device electrode and the active material. Examples of other components include a conductivity-imparting agent, a thickener, and a liquid medium.

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 according to the present embodiment 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) A water-soluble polymer such as a saponified product of a copolymer of an unsaturated carboxylic acid such as acrylic acid, maleic acid and fumaric acid and a vinyl ester can be used. 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.

2.2.3. Liquid medium Since the slurry according to the present embodiment contains the binder composition for an electricity storage device electrode, the slurry contains the liquid medium contained in the binder composition. The slurry according to the present embodiment may further contain a liquid medium in addition to the liquid medium brought from the binder composition.

  The liquid medium additionally contained in the slurry according to this embodiment may be the same as or different from the liquid medium contained in the binder composition for an electricity storage device electrode. The liquid medium additionally contained in the slurry according to the present embodiment is preferably selected from the liquid medium described above for the binder composition.

  The use ratio of the liquid medium (including the amount brought in from the binder composition) in the slurry according to this embodiment is the solid content concentration of the slurry (the total mass of components other than the liquid medium in the slurry accounts for the total mass of the slurry). It is preferable to set it as the ratio used as 30-70 mass%, and it is more preferable to set it as the ratio used as 40-60 mass%.

2.3. Method for Producing Slurry for Electricity Storage Device Electrode The slurry according to the present embodiment may be produced by any method as long as it contains the binder composition for an electricity storage device electrode and an 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 necessary are added to the binder composition and mixed. It is preferable to manufacture by this.

  In order to mix a 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 active material 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. Power Storage Device Electrode The power storage device electrode according to the present embodiment (hereinafter also simply referred to as “electrode”) includes a current collector and an active material prepared using the power storage device electrode slurry on the surface of the current collector Including layers. By applying a slurry produced using the above binder composition to the surface of an appropriate current collector such as a metal foil to form a coating film, and then drying and removing the liquid medium from the coating film An active material layer is formed on the surface of the current collector. In this manner, an electricity storage device electrode in which an active material layer is formed on the surface of the current collector can be manufactured.

  The electrode manufactured in this manner has an active material layer containing the above-described component (A), component (B) and active material, and optional additional components used as necessary on the surface of the current collector. It is what is bound. Therefore, the electricity storage device electrode according to the present embodiment is excellent in the binding property between the current collector and the active material layer, 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. Especially when aluminum is used for the positive electrode and copper is used for the negative electrode, the slurry of the present invention is used. The effect is most apparent. 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 Manufacturing Power Storage Device Electrode An example of a method for manufacturing the power storage device electrode according to the present embodiment is shown below. First, a slurry containing the binder composition and 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 from the coating film. By removing by drying, an active material layer is formed on the surface of the current collector. In this manner, an electricity storage device electrode in which an active material layer is formed on the surface of the current 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 coating amount of the slurry is not particularly limited, but the thickness of the active material layer formed after removing the liquid medium is preferably 5 to 250 μm, more preferably 20 to 100 μm. preferable.

  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 active material layer does not crack due to stress concentration or the active material layer does not peel from the current collector. be able to.

  The heating temperature is preferably in a range where the polyamic acid structure in the coating film is not completely thermally imidized. From such a request, the heating temperature in the step of removing the liquid medium is preferably set to a temperature not exceeding 150 ° C., more preferably not exceeding 130 ° C. The heating time is preferably 0.5 to 30 minutes, and more preferably 1 to 15 minutes.

  Furthermore, it is preferable to increase the density of the active material layer by pressing the active material 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 density of the active material 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 active material 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 more preferably; 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 an active material layer on the surface of the current collector using the slurry according to this embodiment, the process temperature preferably does not exceed 200 ° C., and more preferably does not exceed 180 ° C. Here, the process for forming the active material layer includes the application process of the slurry and the removal process of the liquid medium from the coating film, the optionally performed pressing process, the heating process under reduced pressure, the pressing process, etc. Approximately all of the steps performed by those skilled in the art to form the active material layer are included. The above process temperature refers to the temperature of the slurry, the current collector or the active material layer itself, the temperature of the surrounding atmosphere surrounding them, and the temperature of the device / apparatus in contact with or close to them.
The power storage device electrode manufactured in this way is excellent in the binding property between the current collector and the active material layer, and has a small degree of deterioration of the charge / discharge capacity when the charge / discharge cycle is repeated. .

4). Power Storage Device The power storage device according to the present embodiment 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, but specific examples thereof include propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, fluoroethylene carbonate, and the like. 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. To this flask, 585 g of N-methyl-2-pyrrolidone (NMP) that had been dehydrated by a dehydration distillation method using calcium hydride as a solvent in advance and tetrahydrofuran that had been dehydrated by a dehydration distillation method using metallic sodium ( THF) 585 g, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride 80.56 g (0.250 mol) as tetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether 50 as diamine
. A polymer solution containing 10% by mass of polyamic acid was obtained by charging 06 g (0.250 mol) and reacting at 25 ° C. with stirring for 3 hours. When 193.9 g of a 10% by mass aqueous sodium hydroxide solution (19.39 g (0.485 mol) of sodium hydroxide) was added to the polymer solution thus obtained, a polymer salt (polyamic acid derivative) was added. P1) precipitated. An aqueous solution of the polyamic acid derivative P1 was obtained by dissolving the precipitate dried by filtration with ion-exchanged water so that the polyamic acid derivative P1 was 10% by mass.

<Synthesis Example 2>
In Synthesis Example 1, the amount of NMP used as a solvent was 559 g, methanol (MeOH) subjected to dehydration by dehydration distillation using calcium hydride was 500 g, and tetracarboxylic dianhydride was 3,3 ′, 40.28 g (0.125 mol) of 4,4′-benzophenonetetracarboxylic dianhydride and 27.27 g (0.125 mol) of pyromellitic dianhydride were used as diamines to give 50.4 of 4,4′-diaminodiphenyl ether. A polymer solution containing 10% by mass of polyamic acid was obtained by carrying out the reaction in the same manner as in Synthesis Example 1 except that 06 g (0.250 mol) was used. When 272.1 g of a 10% by mass aqueous potassium hydroxide solution (27.21 g (0.485 mol) of potassium hydroxide) was added to the polymer solution thus obtained, a polymer salt (polyamic acid derivative) was added. P2) precipitated. An aqueous solution of the polyamic acid derivative P2 was obtained by dissolving the precipitate dried by filtration with ion-exchanged water so that the polyamic acid derivative P2 was 10% by mass.

<Synthesis Example 3>
In Synthesis Example 1, the amount of NMP used as a solvent was 942 g, pyromellitic dianhydride 54.53 g (0.250 mol) as tetracarboxylic dianhydride, and 4,4′-diaminodiphenyl ether 50. A polymer solution containing 10% by mass of polyamic acid was obtained by carrying out the reaction in the same manner as in Synthesis Example 1 except that 06 g (0.250 mol) was used. When 116.2 g (11.62 g (0.485 mol) of lithium hydroxide) of a 10 mass% lithium hydroxide aqueous solution was added to the polymer solution thus obtained, a polymer salt (polyamic acid derivative) was added. P3) precipitated. An aqueous solution of the polyamic acid derivative P3 was obtained by dissolving the precipitate dried by filtration with ion-exchanged water so that the polyamic acid derivative P3 was 10% by mass.

<Synthesis Example 4>
In Synthesis Example 1, 1257 g of γ-butyrolactone (GBL) as a solvent, 89.57 g (0.250 mol) of 3,3′4,4′-diphenylsulfonetetracarboxylic dianhydride as a tetracarboxylic dianhydride, diamine A polymer solution containing 10% by mass of polyamic acid was obtained by carrying out the reaction in the same manner as in Synthesis Example 1 except that 50.06 g (0.250 mol) of 4,4′-diaminodiphenyl ether was used. When 65.77 g (0.650 mol) of triethylamine was added to the polymer solution thus obtained, a polymer salt (polyamic acid derivative P4) was precipitated. An aqueous solution of the polyamic acid derivative P4 was obtained by dissolving the precipitate dried by filtration with ion-exchanged water so that the polyamic acid derivative P4 was 10% by mass.

<Synthesis Example 5>
In the same manner as in Synthesis Example 1, 1,300 g of a polymer solution containing 10% by mass of polyamic acid was obtained. To this polymer solution, 3.96 g of pyridine and 5.11 g of acetic anhydride were added, and an imidization reaction was performed with stirring at 110 ° C. for 4 hours. The reaction solution thus obtained was added to methanol for reprecipitation to obtain an imidized polymer of polyamic acid as a white solid. The obtained imidized polymer of polyamic acid was dissolved in NMP so as to be 10% by mass to obtain a polymer solution of an imidized polymer of polyamic acid. The solution viscosity of this polymer solution was 8,200 mPa · s, and the imidation ratio of the polymer contained in the polymer solution was 20%.

The imidation rate was determined by ¹ H-NMR measured at room temperature using tetramethylsilane as a reference substance by dissolving a polymer recovered by removing the solvent from the obtained polymer solution under reduced pressure and deuterated dimethyl sulfoxide. From the chart of (2), it was determined by the following formula (1).
Imidation ratio (%) = (1- (A1 / A2) × α) × 100 (1)
(In the above formula (1), A1 is a peak area derived from protons of NH groups appearing near a chemical shift of 10 ppm, A2 is a peak area derived from other protons, and α is a precursor of an imidized polymer. (This is the ratio of the number of other protons to one proton of the NH group in the polyamic acid or polyamic acid derivative.)

  When 25.55 g (0.3 mol) of piperidine was added to the polymer solution thus obtained, a polymer salt (imidized polymer P5 of polyamic acid derivative) was precipitated. The precipitate obtained by filtration and drying was dissolved in 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.

<Synthesis Example 6>
In Synthesis Example 1, 80.56 g (0.250 mol) of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride as tetracarboxylic dianhydride and 4,4′-diaminodiphenylmethane as diamine 49. A polymer solution containing 10% by mass of polyamic acid was obtained by carrying out the reaction in the same manner as in Synthesis Example 1 except that 37 g (0.249 mol) was used. When 19.40 g (0.485 mol) of NaOH was added to the polymer solution thus obtained, a polymer salt (polyamic acid derivative P6) was precipitated. The precipitate obtained by filtration drying was dissolved in ion-exchanged water so that the polyamic acid derivative P6 was 10% by mass, thereby obtaining a polymer aqueous solution of the polyamic acid derivative P6.

<Synthesis Example 7>
In Synthesis Example 1, 80.24 g (0.249 mol) of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride as tetracarboxylic dianhydride and 4,4′-diaminodiphenylmethane 49. A polymer solution containing 10% by mass of polyamic acid was obtained by carrying out the reaction in the same manner as in Synthesis Example 1 except that 57 g (0.250 mol) was used. When 27.21 g (0.485 mol) of KOH was added to the polymer solution thus obtained, a polymer salt (polyamic acid derivative P7) was precipitated. The precipitate obtained by filtration drying was dissolved in ion exchange water so that the polyamic acid derivative P7 was 10% by mass, thereby obtaining a polymer aqueous solution of the polyamic acid derivative P7.

<Synthesis Example 8>
In Synthesis example 1, 80.24 g (0.249 mol) of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride as tetracarboxylic dianhydride and 3,5-diaminobenzoic acid as diamine A polyamic acid was obtained by carrying out the reaction in the same manner as in Synthesis Example 1 except that 48 g (0.24 mol) and 1.48 g (0.01 mol) of 1,3-bis-3-aminopropyltetramethyldisiloxane were used. A polymer solution containing 10% by mass was obtained. To this polymer solution, 0.2 g of isoquinoline and 60 mL of toluene were added, the temperature of the solution was raised to 180 ° C., and the reaction was performed while removing by-product water to obtain an imidized polymer solution of polyamic acid. When this was allowed to cool and then 27.21 g (0.485 mol) of KOH was added, a polymer salt (imidized polymer P8 of polyamic acid derivative) was precipitated. This precipitate was filtered and dried, and dissolved in ion-exchanged water so that the imidized polymer P8 of the polyamic acid derivative was 10% by mass, thereby obtaining an aqueous solution of the imidized polymer P8 of the polyamic acid derivative.

5.2. Synthesis of active material <Synthesis Example 9>
A mixture of pulverized silicon dioxide powder (average particle size 10 μm) and carbon powder (average particle size 35 μm) was placed in an electric furnace adjusted to a temperature in the range of 1,100 to 1,600 ° C. under a nitrogen stream (0 0.5 NL / min), heat treatment was performed for 10 hours to obtain a silicon oxide powder (average particle size 8 μm) represented by the composition formula SiOx (x = 0.5 to 1.1). 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 as component (A) in an Ar-substituted glove box (polyamic acid derivative P1) A binder composition was prepared by adding 1.124 μL (0.001 g) of tetrahydrofuran (THF) to a solution containing 10 g of the mixture using a microsyringe.

(2) Adhesion test of binder composition for electricity storage device electrode The binder composition prepared above was applied on a 10 cm square copper plate and a glass plate so that the film thickness after solvent removal was 90 μm. By heating at 150 ° C. for 15 minutes, a thin film of a binder was formed on each of the copper plate and the glass plate. The two types of binder thin films formed above were each subjected to a cross-cut peel test in accordance with JIS K5400. Specifically, using a cutter, 11 cuts were made from the surface of the thin film to the depth reaching the copper plate or the glass plate at 1 mm intervals, both vertically and horizontally, and the thin film was divided into a grid-like area of 100 squares. An adhesive tape (manufactured by Terraoka Co., Ltd., product number “650S”) was applied to the entire surface of these 100 square areas and immediately peeled off, and the number of remaining squares was counted. The evaluation results are shown in Table 1 as the number of remaining cells in 100 cells. When the number of remaining cells is 80 or more, it can be determined that the adhesion is good, and when the number of cells remaining is less than 80, the adhesion can be determined as poor.

  In addition, from the examination by the present inventors, it is empirically clear that the adhesion between the active material layer and the current collector is proportional to the adhesion between the copper plate and the polymer film in this test. It has become. Further, it has been empirically revealed that the binding property as a binder for binding active materials is proportional to the adhesion between the glass plate and the polymer film in this test. For this reason, when the adhesion between the glass plate and the polymer film is good, it can be estimated that the adhesion as a binder of the polymer that binds the active materials is good, and the copper plate and the polymer film are heavy. When the adhesion between the combined films is good, it can be estimated that the adhesion between the current collector and the active material layer is good. In this case, if the number of remaining squares is 80 or more, it can be determined that the adhesion is good, and if this number is 90 or more, it can be determined that the adhesion is excellent. . The number of remaining cells is most preferably 100 out of 100 grids.

(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 graphite-coated silicon oxide prepared in Synthesis Example 9 above, and acetylene black (electrochemical industry) as a conductive agent 1 part by mass was added and mixed for 3 minutes at 20 rpm. Next, 100 parts by mass of the binder composition prepared above and 20 parts by mass of water were added, 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 On the surface of a current collector made of copper foil having a thickness of 10 μm, the slurry prepared above was formed into a film so that the mass of the active material layer after solvent removal was 4.50 mg / cm ^2. The thickness was adjusted and uniformly applied by a 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 / min. And the density of the active material layer was adjusted to 1.60 g / cm ³ . Furthermore, an electricity storage device electrode was obtained by forming an active material layer by heating at 160 ° C. for 6 hours under a reduced pressure of 100 Pa absolute pressure. The density of the active material layer in this electricity storage device electrode was 1.62 g / cm ³ .

(5) Production of electricity storage device In the glove box substituted with argon so that the dew point is -80 ° C. or lower, the electrode produced above is punched and molded to a diameter of 15.5 mm, with the active material layer facing upward, It was placed on a two-pole 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 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 was placed as a counter electrode, and the outer body of the bipolar coin cell was sealed with a screw to seal the lithium ion A 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). This operation was repeated to produce a total of two electricity storage devices. One of them was subjected to “(6) Evaluation of electricity storage device (evaluation of charge / discharge cycle characteristics)”, and the other was subjected to “(7) Evaluation of film thickness change rate of active material layer”.

(6) Evaluation of electricity storage device (Evaluation of 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. This charge and discharge of 0.5C is repeated, and when the 0.5C discharge capacity at the 100th cycle is B, the capacity retention rate after 100 cycles is expressed by the following formula (
Calculated according to 2).
Capacity maintenance rate (%) = (B / A) × 100 (2)
The evaluation results are shown in Table 1. 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.

(7) Evaluation of film thickness change rate of active material layer About the electricity storage device obtained above, charging was started at a constant current (0.2 C), and when the voltage reached 0.01 V, a constant voltage (0 The charging was continued at .01 V), and charging was completed (cut off) when the current value reached 0.05C. 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, about the said electrical storage device which performed initial charge / discharge, charge starts with a constant current (0.2C), and when a voltage becomes 0.01V, it charges with a constant voltage (0.01V) continuously. Continuing, the time when the current value reached 0.05 C was defined as the completion of charging (cut-off). The electricity storage device was disassembled in a dry room (room temperature 25 ° C.) having a dew point of −60 ° C. or less, and an electricity storage device electrode (negative electrode) was taken out. Subsequently, this electrode was immersed in dimethyl carbonate for 1 minute and washed in a dry room. After taking out the electrode from dimethyl carbonate, the dimethyl carbonate was vaporized and removed by standing in a dry room for 30 minutes. The thickness of the active material layer of the electrode after charging is measured, and the ratio of the thickness of the active material layer of the electrode after charging to the thickness of the active material layer of the electrode immediately after manufacture (uncharged state) measured in advance is It was calculated by the following formula (3).
Film thickness ratio after charge (%) = (film thickness after charge / film thickness immediately after manufacture) × 100 (3)
The evaluation results are shown in Table 1. When this value exceeds 120%, the active material layer indicates that the volume expansion of the active material accompanying charging is not relaxed, and there is a concern that the active material may be peeled off when mechanical stress is applied to the active material. is there. On the other hand, if this value is 120% or less, it indicates that the active material is firmly held in the active material layer despite the volume expansion of the active material with charging, and the active material is peeled off. It can be evaluated that the electrode is a good electrode with suppressed.

5.4. Examples 2-7, 9-11 and Comparative Examples 1-3
In the said Example 1, the 10 mass% polymer aqueous solution obtained in any one of the said synthesis examples 1-8 was used so that the kind and quantity of (A) component might respectively become as Table 1. A binder composition for an electricity storage device electrode was prepared in the same manner as in Example 1 except that the amount of component (B) added was as shown in Table 1 or Table 2. Using each of these 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.

5.5. Example 8
In Example 1 above, a commercially available polyamic acid (manufactured by Ube Industries, Ltd., trade name “U-varnish A”, polyamic acid NMP solution) is used as the component (A), and the amount of the component (B) added is A binder composition for an electricity storage device electrode was prepared in the same manner as in Example 1 except that it was as described in Table 1. Using this binder composition, 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.

5.6. Evaluation results Tables 1 and 2 below show the evaluation results of the examples and comparative examples.

Abbreviations of each component in Table 1 and Table 2 represent the following compounds, respectively. Moreover, "-" in Table 1 represents that the corresponding component is not contained.
<(A) component>
UVA: U-varnish A (trade name, manufactured by Ube Industries, Ltd., NMP solution of polyamic acid)
<(B) component>
・ THF: Tetrahydrofuran

  As is clear from Table 1 and Table 2 above, the binder compositions according to the present invention shown in Examples 1 to 11 contain silicon atoms as active materials compared to the binder compositions of Comparative Examples 1 to 3. Even when the active material is included, it has been found that the bonding ability between the active materials and the adhesion ability between the active material and the current collector are excellent. Moreover, the electrode produced using the binder composition which concerns on this invention shown in Examples 1-11 is hard to change the film thickness of the active material layer before and behind charge, The electrical storage device produced using this electrode It was found that the discharge capacity after 100 cycles can be maintained at a high level.

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 (3)

(A) at least one polymer selected from the group consisting of a polyamic acid, a polyamic acid derivative, and an imidized polymer thereof;
(B) at least one compound selected from the group consisting of aliphatic ethers and aliphatic alcohols,
When the content of the component (B) is Mb parts by mass and the content of the component (A) is Ma parts by mass, the Mb / Ma value is 0.00001 to 1 for a lithium ion secondary battery negative electrode A binder composition;
A slurry for a lithium ion secondary battery negative electrode, comprising an active material containing silicon atoms . Current collector and said comprises an active material layer created using the lithium ion secondary battery negative electrode slurry according to claim 1 to the surface of the current collector, the lithium-ion secondary battery negative electrode. A lithium ion secondary battery comprising the lithium ion secondary battery negative electrode according to claim 2 .