JP7339404B2 - Dispersant composition for electricity storage device electrode - Google Patents

Description

TECHNICAL FIELD The present invention relates to a dispersant composition for electricity storage device electrodes.

BACKGROUND ART In recent years, electric vehicles that do not emit carbon dioxide have been actively developed from the viewpoint of global warming suppression. Compared to gasoline vehicles, electric vehicles have short mileage and take a long time to charge their batteries. In order to shorten the charging time, it is necessary to speed up the movement of electrons in the positive electrode. At present, carbon materials are used as conductive materials in positive electrodes for non-aqueous electrolyte batteries. However, when a carbon material is used, the viscosity of the conductive material slurry or the positive electrode paste becomes high, which poses a problem in handleability, and it is desired to reduce the viscosity of the slurry or paste. The degree of viscosity of the slurry or paste is greatly affected by the dispersibility of the carbon material.

Patent Document 1 discloses a dispersant used in a non-aqueous polar solvent obtained by reacting a copolymer of diisobutylene and maleic anhydride with ammonia or a saturated lower amine at a reaction rate of almost 100%. ing.
Patent Document 2 discloses a dispersant composition for printing inks containing a 100% amidated product of a copolymer of diisobutylene and maleic anhydride with stearylamine and methyl isobutyl ketone (MIBK) as an organic solvent.
Patent Document 3 discloses an oil dispersant composition for electronic materials containing an amidated product of a copolymer of diisobutylene and maleic anhydride with oleylamine and propylene glycol methyl ether acetate (PEGMA) as an organic solvent.

Japanese Patent Publication No. 41-17852 JP 2018-168285 A JP 2009-138115 A

In Patent Document 1, as a dispersant used for a carbon material, a dispersant introduced with a long-chain alkyl group is particularly effective in a non-polar solvent, and a dispersant introduced with a short-chain alkyl group is particularly effective in a polar solvent. It is On the other hand, while further reduction in resistance of electrodes for storage battery devices due to good dispersibility of carbon materials is desired, Patent Document 1 discloses that short-chain alkyl groups are effective for dispersing carbon black. is introduced, there is a problem that the dispersibility of the carbon material-based conductive material in the polar solvent used in the production of electrodes for storage battery devices is low. This problem is particularly pronounced when the carbon material is a carbon nanotube with a high aspect ratio.
Therefore, in order to form a positive electrode coating film with low resistance, it is desired to provide a dispersant capable of highly dispersing a carbon material-based conductive material even in a polar solvent used for preparing a positive electrode paste.
The dispersant described in Patent Document 2 is methyl isobutyl ketone (MIBK), and the dispersant described in Patent Document 3 is propylene glycol methyl ether acetate, both of which are used in a polar solvent having a low dielectric constant. However, none of these solvents can achieve good dispersibility due to their low dielectric constants, and cannot be used to prepare positive electrode pastes.

Accordingly, in one aspect, the present disclosure provides a dispersant composition for electricity storage device electrodes that enables preparation of a conductive material slurry in which a carbon material-based conductive material has good dispersibility. Also provided are a conductive material slurry and a positive electrode paste containing the dispersant composition for an electricity storage device electrode.
The present disclosure also provides a method for producing a positive electrode for an electricity storage device using the positive electrode paste, and a method for producing an electricity storage device using the positive electrode for an electricity storage device.

ただし、上記一般式（１）中、
Ｒ¹は、水素又はメチル基であり、
Ｒ²は、水素、Ｃ_nＨ_2n+1、ｉ－Ｃ_nＨ_2n+1、Ｃ₆Ｈ₅又は置換基を有する若しくは有さない芳香族基であり、ｎは１～１０であり、
Ｒ³は、Ｃ_mＨ_2m+1又はｉ－Ｃ_mＨ_2m+1であり、ｍは１６～２２であり、
Ｍは、水素、ＮＨ₄、前記有機溶媒に可溶な塩を与える金属又は前記有機溶媒に可溶な有機アンモニウムであり、
ａ，ｂは、各々、ａ＋ｂ＝１として表されるモル分率であり、０．５０≦ｂ≦１．００を満たす。 In one aspect, the present disclosure includes a polymer including a repeating unit represented by the following general formula (1) and an organic solvent, and the organic solvent has a dielectric constant of 25.0 or more and 35.0 at 25°C. It is related with the dispersing agent composition for electrical storage device electrodes which are the following.

However, in the above general formula (1),
R ¹ is hydrogen or a methyl group;
R ² is hydrogen, C _n H _2n+1 , iC _n H _2n+1 , C ₆ H ₅ or an aromatic group with or without a substituent, n is 1 to 10;
R ³ is C _m H _2m+1 or iC _m H _2m+1 and m is 16 to 22;
M is hydrogen, _NH4 , a metal that provides a salt soluble in said organic solvent or an organic ammonium soluble in said organic solvent;
Each of a and b is a molar fraction expressed as a+b=1 and satisfies 0.50≦b≦1.00.

In one aspect, the present disclosure is a carbon material-based conductive material slurry containing the power storage device electrode dispersant composition of the present disclosure and a carbon material-based conductive material, wherein the organic The present invention relates to a carbon material-based conductive material slurry in which the dielectric constant at 25° C. of the solvent is 25.0 or more and 35.0 or less.

In one aspect, the present disclosure is a positive electrode paste for an electrical storage device comprising the dispersant composition for an electrical storage device electrode of the present disclosure, a positive electrode active material, and a carbon material-based conductive material, and is included in the positive electrode paste for an electrical storage device. It relates to a positive electrode paste for an electricity storage device, wherein the organic solvent containing the organic solvent has a dielectric constant of 25.0 or more and 35.0 or less at 25°C.

In one aspect, the present disclosure relates to a method for manufacturing a positive electrode for a power storage device using the positive electrode paste for a power storage device of the present disclosure.

In one aspect, the present disclosure relates to a method for manufacturing an electricity storage device using the positive electrode for an electricity storage device of the present disclosure.

ADVANTAGE OF THE INVENTION According to one aspect of the present disclosure, it is possible to provide a dispersant composition for an electricity storage device electrode that enables the preparation of a conductive material slurry having good dispersibility of a carbon material-based conductive material.
According to the present disclosure, in one aspect, it is possible to provide a carbon material-based conductive material slurry in which the dispersibility of the carbon material-based conductive material is good, since the power storage device electrode dispersant composition of the present disclosure is included.
According to the present disclosure, in one aspect, the power storage device electrode dispersant composition of the present disclosure is included, so that it is possible to provide a power storage device positive electrode paste capable of forming a positive electrode coating film having a small resistance value.
According to the present disclosure, in one aspect, the power storage device positive electrode is produced using the power storage device positive electrode paste of the present disclosure, so that the power storage device positive electrode having a reduced resistance can be manufactured.
According to the present disclosure, in one aspect, an electricity storage device is manufactured using the positive electrode for an electricity storage device of the present disclosure, so that an electricity storage device with reduced resistance can be manufactured.

The present disclosure provides an organic solvent having a high dielectric constant, specifically a dielectric constant of 25.0 to 35.0 at 25° C. for a polymer having a long-chain alkyl group with 16 to 22 carbon atoms. It is based on the new finding that the use of the following organic solvent improves the dispersibility of the carbon material-based conductive material in the conductive material slurry.

Although the details of the mechanism by which the effects of the present disclosure are manifested are not clear, it is speculated as follows.
In order for the dispersant, which is a polymer, to exhibit excellent adsorptivity to the carbon material-based conductive material, the dispersant must have a side chain with a specific chain length, specifically, a long chain with 16 or more and 22 or less carbon atoms. It has been found necessary to contain an alkyl group. On the other hand, it is generally believed that when a polymer contains a long-chain alkyl group with the above-mentioned specific chain length, the hydrophobicity of the polymer increases, and the solubility in polar solvents decreases. However, it has been found that polymers containing long-chain alkyl groups R ³ of specific chain lengths are appropriately soluble in polar solvents with specific dielectric constants. It is speculated that this is because the long-chain alkyl group ^R3 is solvated in a polar solvent having a specific dielectric constant, thereby suppressing the hydrophobic interaction between the long-chain alkyl groups. ing. Then, the combination of the chain length of the long-chain alkyl group R ³ and the dielectric constant of the polar solvent improves the solubility of the polymer in the polar solvent, and the constituent components in the following general formula (1) are each the following (a ) to (c), the carbon material-based conductive material can be highly dispersed.
(a) The introduction amount of the long-chain alkyl group R ³ satisfies 0.50 ≤ b ≤ 1.00 in the following general formula (1), so that the dispersant exhibits high adsorptivity to the carbon material-based conductive material. do.
(b) R ¹ and R ² contribute to the solubility of the polymer in polar solvents with specific dielectric constants.
(c) The carboxyl group derived from maleic anhydride generated by the introduction of the long-chain alkyl group ^R3 , or a salt structure obtained by neutralizing this with ammonia or amines, has a specific dielectric constant due to its electrostatic repulsion. It contributes to improving the dispersibility of the carbon material-based conductive material in the polar solvent.
However, the present disclosure should not be construed as being limited to these mechanisms.

ただし、上記一般式（１）中、
Ｒ¹は、水素又はメチル基であり、
Ｒ²は、水素、Ｃ_nＨ_2n+1、ｉ－Ｃ_nＨ_2n+1、Ｃ₆Ｈ₅又は置換基を有する若しくは有さない芳香族基であり、ｎは１～１０であり、
Ｒ³は、Ｃ_mＨ_2m+1又はｉ－Ｃ_mＨ_2m+1であり、ｍは１６～２２であり、
Ｍは、水素、ＮＨ₄、前記有機溶媒に可溶な塩を与える金属又は前記有機溶媒に可溶な有機アンモニウムであり、
ａ，ｂは、各々、ａ＋ｂ＝１として表されるモル分率であり、０．５０≦ｂ≦１．００を満たす。 <Dispersant composition for electricity storage device electrode>
In one aspect, the present disclosure includes a polymer including a repeating unit represented by the following general formula (1) and an organic solvent, and the organic solvent has a dielectric constant of 25.0 or more and 35.0 or less at 25°C. , a dispersant composition for electricity storage device electrodes (hereinafter sometimes abbreviated as “the dispersant composition of the present disclosure”).

However, in the above general formula (1),
R ¹ is hydrogen or a methyl group;
R ² is hydrogen, C _n H _2n+1 , iC _n H _2n+1 , C ₆ H ₅ or an aromatic group with or without a substituent, n is 1 to 10;
R ³ is C _m H _2m+1 or iC _m H _2m+1 and m is 16 to 22;
M is hydrogen, _NH4 , a metal that provides a salt soluble in said organic solvent or an organic ammonium soluble in said organic solvent;
Each of a and b is a molar fraction expressed as a+b=1 and satisfies 0.50≦b≦1.00.

In one aspect, the dispersant composition of the present disclosure includes a polymer that satisfies 0.50≦b≦1.00 in general formula (1) above, and an organic solvent. The organic solvent has a dielectric constant of 25.0 or more and 35.0 or less at 25°C.

By using the dispersant composition of the present disclosure, it is possible to prepare a conductive material slurry in which the carbon material-based conductive material has good dispersibility. It is possible to provide a positive electrode paste for an electricity storage device that can form a positive electrode coating film with a small value.

(Polymer)
The polymer containing the repeating unit represented by the general formula (1) (hereinafter referred to as "polymer A" for convenience of explanation) contained in the dispersant composition of the present disclosure is a dispersant. Polymer A introduces a long-chain alkyl group ^R3 by amidating a copolymer ^of olefin and maleic anhydride. obtained by neutralization.

The repeating unit represented by the general formula (1) includes a structural unit I represented by the following general formula (2) and a structural unit II represented by the following general formula (3). The arrangement of the structural unit I and the structural unit II in the repeating unit represented by the general formula (1) may be either block type or random type, but from the viewpoint of polymer productivity, random type preferable.

Structural unit I and structural unit II both contain a unit represented by the following general formula (4). The unit is a component derived from an olefin and responsible for solubility in organic solvents. M, which constitutes structural unit II, is a component that contributes to the dispersion of the carbon material-based conductive material in an organic solvent. R ³ constituting structural unit II is a hydrophobic group and is a component that functions as an adsorptive group for the carbon material-based conductive material.

In general formula (4) above, R ¹ is hydrogen or a methyl group, preferably a methyl group from the viewpoint of solubility in organic solvents.

In the above general formula (4), R ² is hydrogen, C _n H _2n+1 , iC _n H _2n+1 , C ₆ H ₅ or having a substituent or unsubstituted aromatic group, preferably C _n H _2n+1 , iC _n H _2n+1 , C ₆ H ₅ , or an aromatic group with or without a substituent, more preferably is C _n H _2n+1 , iC _n H _2n+1 or a substituted or unsubstituted naphthyl or phenyl group, more preferably C _n H _2n+1 or iC _n H It is _2n+1 .

The carbon number n of R ² is 1 or more, preferably 2, from the viewpoints of the adsorptivity of the polymer A to the carbon material-based conductive material, the ease of synthesizing the polymer A, and the availability of the monomer. From the same point of view, it is 10 or less, preferably 7 or less.

Of the structural units II, the following general formula (5) is obtained by amidating the unit represented by the following formula (6) to introduce a long-chain alkyl group ^R3 and, if necessary, neutralizing the carboxyl group. be.

In general formula (5) above, R ³ is C _m H _2m+1 or iC _m H _2m+1 . The carbon number m of R ³ is 16 or more, preferably 18 or more, from the viewpoint of adsorptivity to a carbon material-based conductive material, and from the same viewpoint, 22 or less, preferably 20 or less. be.

From the viewpoint of dispersibility, the polymer A may be unneutralized, partially neutralized in which some of the carboxy groups generated by the introduction of R ³ are neutralized, or neutralized in which all are neutralized. . In the above general formula (5), from the viewpoint of the dispersibility of the carbon material-based conductive material, M is, for example, hydrogen, NH ₄ , a metal that provides a salt soluble in the organic solvent, or an organic solvent soluble in the organic solvent. Ammonium and the like are preferred, and hydrogen is more preferred.

Polymer A is an amidated copolymer of olefin and maleic anhydride, and b is the molar fraction when a+b=1, and is also called amidation rate or modification rate. In the relational expression 0.50 ≤ b ≤ 1.00, when b is 0.50, the modification rate b from the unit represented by the above formula (6) to the unit represented by the above general formula (5) is When b is 1, it means that the modification rate b is 100 mol %.

In the polymer A, b is 0.50 or more, preferably 0.55 or more, more preferably 0.60 or more, and still more preferably 0.65, from the viewpoint of improving the adsorptivity to the carbon material-based conductive material. above, more preferably 0.70 or more, and still more preferably 1.00. The polymer A may be one or a mixture of two or more selected from those having a modification ratio b of 0.50 to 1.00.
In addition, in the present disclosure, the modification rate b can be calculated from the amount of the amine compound used for the later-described monomer II used for the polymerization of the polymer A.

The monomer that provides the unit represented by the general formula (4) (hereinafter also referred to as "monomer I") is, from the viewpoint of good solubility in organic solvents, α-olefins having 2 to 13 carbon atoms. At least one selected from the group consisting of diisobutylene, isobutylene, 1-pentene, 1-heptene, 1-butene, 1-octene, 1-decene, styrene, α-methylstyrene and the like is preferred. Among these, from the viewpoint of good solubility in organic solvents, at least one of styrene, diisobutylene (2,4,4-trimethylpentene-1) and isobutylene is preferred, and diisobutylene (2,4, 4-trimethylpentene-1) is more preferred.

Examples of the monomer that provides the unit represented by the general formula (6) (hereinafter also referred to as "monomer II") include maleic anhydride and maleic acid, and the reason is that an alkyl group can be easily introduced by amidation. Therefore, a monomer having a reactive structure such as an acid anhydride is preferable, and maleic anhydride is preferable.

Polymer A can be prepared, for example, by methods used for the polymerization of vinyl monomers. For example, the monomer I and the monomer II are mixed in a solvent, and the monomers are ^polymerized by a solution polymerization method. An alkyl group R ³ having 16 to 22 carbon atoms is introduced into some or all of the derived structural units.
If necessary, a neutralizing agent is used to neutralize all or part of the carboxylic acid in the solution containing the modified copolymer thus obtained. After that, if necessary, the solvent in the solution containing the modified copolymer is replaced with an aqueous solvent to precipitate the modified copolymer to obtain the dispersant (polymer A) of the present disclosure.

Amine compounds having an alkyl group R ³ having 16 to 22 carbon atoms include cetylamine, stearylamine, icosylamine and behenylamine.

Solvents used in the synthesis of polymer A include, for example, hydrocarbons (hexane, heptane), aromatic hydrocarbons (toluene, xylene, etc.), ketones (acetone, methyl ethyl ketone), ethers (tetrahydrofuran, diethylene glycol dimethyl ether), N- Organic solvents such as methylpyrrolidone can be used. The amount of the solvent is preferably 0.5 to 10 times the mass ratio of the total amount of the monomers.

As the polymerization initiator used for the polymerization, known radical polymerization initiators can be used, for example, azo polymerization initiators, hydroperoxides, dialkyl peroxides, diacyl peroxides, ketone peroxides. etc. The amount of polymerization initiator is preferably 0.01 to 5 mol % with respect to the total amount of monomer components. The polymerization reaction is preferably carried out at a temperature of 40 to 180° C. under nitrogen stream, and the reaction time is preferably 0.5 to 20 hours. Moreover, a known chain transfer agent can be used in the polymerization. Chain transfer agents include, for example, isopropyl alcohol and mercapto compounds such as mercaptoethanol.

M in the dispersant (Polymer A) of the present disclosure is hydrogen, _NH4 , a metal that provides a salt soluble in said organic solvent, or an organic ammonium derived from an organic amine soluble in said organic solvent, Examples of the structure-imparting neutralizing agent include ammonia, organic amine B1, and alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.

A specific example of ^the organic amine B1 is ^not particularly limited as long as it functions as a neutralizing agent. 6.3°C, the same shall apply hereinafter), dimethylamine (7.80°C, 7°C), ethylamine (7.93°C, 16.6°C), dimethylbenzylamine (9.1°C, boiling point 180°C), methylbenzylamine (9.8°C, 186°C), 2-N-dibutylaminoethanol (10.0, 226°C), 1-phenylmethanamine (10.5, 184°C), N,N-diethylaminoethanol (10.7, 162°C), 2-dimethylaminoethanol (11.3 , 134°C), 1-amino-2-butanol (11.9, 169°C), 2-(ethylamino)ethanol (12.0, 169°C), 2-amino-2-methyl-1-propanol (12.2, 169°C) 185°C), DL-1-amino-2-propanol (12.4, 160°C), N-methyl-2-aminoethanol (12.5, 175°C), 1-(2-hydroxyethyl)piperazine (12.98, 246°C) and N-ethyldiethanolamine (13.4, 251°C).
The SP value is defined by the theoretical development of a regular solution, and is used as an index showing the solubility of a compound. The SP value referred to in the present disclosure is in accordance with the Fedors calculation method, which is one of the methods for estimating from the molecular structure. Both the Solubility Parameters and Molar Volumes of Liquids").

The dispersant (polymer A) of the present disclosure is a modified copolymer obtained by optionally neutralizing an amidated copolymer of olefin and maleic anhydride. The weight average molecular weight of the copolymer of and maleic anhydride is preferably 3,000 or more, more preferably 5,000 or more, and even more preferably 6,000 or more, from the viewpoint of adsorption to the carbon material-based conductive material. , and from the viewpoint of the solubility of the polymer A in an organic solvent, the dispersibility of the carbon material-based conductive material, and the low viscosity of the slurry, it is preferably 100,000 or less, more preferably 70,000 or less, and 50,000 or less. is more preferred. In the present disclosure, the weight average molecular weight of the copolymer of olefin and maleic anhydride before amide modification is a value measured by GPC (gel permeation chromatography), and the details of the measurement conditions are as shown in Examples. be.

From the viewpoint of productivity, the content of polymer A in the dispersant composition of the present disclosure is preferably 0.1% by mass or more, more preferably 1% by mass or more, still more preferably 10% by mass or more, and still more It is preferably 15% by mass or more, still more preferably 20% by mass or more, and from the viewpoint of the solubility of polymer A in an organic solvent, preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably is 40% by mass or less. When polymer A is a combination of two or more, the content of polymer A is their total content.

(Organic amine B2)
In one aspect, the dispersant composition of the present disclosure is an organic solvent-soluble organic amine (for synthesis of polymer A Also referred to as “organic amine B2 of the present disclosure” to distinguish from the organic amine B1 used) is preferably added. The organic amine B2 is preferably an amine compound having an SP value of 9.5 (cal/cm ³ ) ^1/2 or more and 14.0 (cal/cm ³ ) ^1/2 or less from the viewpoint of reducing the DC resistance of the electricity storage device. , the boiling point is preferably 260° C. or lower from the viewpoint of suppressing residue on the electrode.

The SP value of the organic amine B2 of the present disclosure is preferably 9.5 (cal/cm ³ ) ^1/2 or more, more preferably 10.5 (cal/cm ³ ) ¹ from the viewpoint of reducing the DC resistance of the electricity storage device. ^/2 or more, more preferably 11.0 (cal/cm ³ ) ^1/2 or more, and preferably 14.0 (cal/cm ³ ) ^1/2 or less, more preferably 13.5 (cal/ cm ³ ) ^1/2 or less, more preferably 13.0 (cal/cm ³ ) ^1/2 or less.

The boiling point of the organic amine B2 of the present disclosure is preferably 260 ° C. or less, but from the viewpoint of reducing the resistance of the electrode of the electricity storage device, it is preferably a temperature at which it volatilizes during drying in the manufacturing process of the electrode. It is more preferably not higher than the boiling point of N-methylpyrrolidone (NMP), which is frequently used as a solvent (boiling point: 202°C), and more preferably not higher than 190°C from the viewpoint of reusing NMP. The lower limit of the boiling point of the organic amine B2 of the present disclosure is preferably 100° C. or higher, more preferably 120° C. or higher, from the viewpoint of handleability.

Preferred specific examples of the organic amine B2 of the present disclosure have an SP value of 9.5 (cal/cm ³ ) ^1/2 among the preferred specific examples of the organic amine B1, from the viewpoint of reducing the DC resistance of the electricity storage device. An amine compound having a concentration of 14.0 (cal/cm ³ ) ^1/2 or less and a boiling point of 260° C. or less is preferable. Among these, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, At least one selected from the group consisting of 2-N-dibutylaminoethanol, 1-phenylmethanamine, 2-dimethylaminoethanol, N-methyl-2-aminoethanol, and N-ethyldiethanolamine is preferred, and 2-dimethylamino At least one selected from the group consisting of ethanol, 2-amino-2-methyl-1-propanol, and N-methyl-2-aminoethanol is more preferred, and 2-amino-2-methyl-1-propanol is particularly preferred. .

In one or more embodiments, the content of the organic amine B2 in the dispersant composition of the present disclosure is the polymer A100 from the viewpoint of reducing the viscosity of the conductive material slurry and the positive electrode paste and reducing the direct current resistance of the electricity storage device. With respect to parts by mass, preferably 10 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 30 parts by mass or more, still more preferably 50 parts by mass or more, still more preferably 70 parts by mass or more, and , From the viewpoint of the solubility of the polymer A, preferably 300 parts by mass or less, more preferably 250 parts by mass or less, even more preferably 200 parts by mass or less, still more preferably 150 parts by mass with respect to 100 parts by mass of the polymer A It is below.

The mass ratio A/B2 between the polymer A of the present disclosure and the organic amine B2 of the present disclosure in the dispersant composition of the present disclosure is preferably 0.1 or more, and 0.1 or more, from the viewpoint of improving the dispersibility of the conductive material. 3 or more is more preferable, 0.5 or more is still more preferable, 0.8 or more is even more preferable, and from the viewpoint of high conductivity, 10 or less is preferable, 5 or less is more preferable, and 3 or less is even more preferable.

[Organic solvent]
In one or more embodiments, the dispersant composition of the present disclosure is an organic solvent having a dielectric constant (εr) of 25.0 or more and 35.0 or less at 25° C. (hereinafter, for convenience of explanation, “organic solvent C ).

Relative permittivity (εr) is an index representing the polarity of a solvent, and is the ratio (ε/ε ₀ ) of the permittivity of solvent (ε) to the permittivity of vacuum (ε ₀ ). It can be measured with a commercially available measuring device such as Model 871 permittivity measuring device manufactured by Sanyo Boeki Co., Ltd. In addition, the values are described in "Kagaku Binran, Basic Edition, Revised 5th Edition", 2004, pp.I-770-777, etc., and these can be used as a reference.

The larger the value of the relative dielectric constant (εr), the more polar the solvent becomes. It is 29.0 or more and 35.0 or less, preferably 34.0 or less, more preferably 33.0 or less.

The organic solvent C is preferably one capable of dissolving the binder (binder resin) contained in the positive electrode paste. Examples of the organic solvent C include amide-based polar organic solvents such as N-methylpyrrolidone (NMP, εr=32.2). Among them, NMP is preferred because of its high solubility.

The dispersant composition of the present disclosure may further contain other components as long as the effects of the present disclosure are not hindered. Other components include, for example, antioxidants, neutralizers, antifoaming agents, preservatives, dehydrating agents, rust preventives, plasticizers, binders, and the like.

<Carbon material-based conductive material slurry>
The present disclosure, in one aspect, relates to a carbon material-based conductive material slurry (hereinafter also referred to as "conductive material slurry of the present disclosure") containing a carbon material-based conductive material and a dispersant composition of the present disclosure. Preferred forms of the dispersant composition of the present disclosure in this aspect are described above. In one or more embodiments, the conductive material slurry of the present disclosure includes a polymer A, an organic solvent C, a carbon material-based conductive material described later (hereinafter also referred to as “conductive material D”), and, if necessary, an additional Contains organic solvent and organic amine B2. The additional organic solvent is also preferably an organic solvent having a dielectric constant of 25.0 or more and 35.0 or less. Since the conductive material slurry of the present disclosure contains the dispersant composition of the present disclosure, it has a low viscosity, the dispersed particle size of the carbon material-based conductive material is small, and the carbon material-based conductive material has good dispersibility.

(Carbon material-based conductive material)
In one or more embodiments, the carbon material-based conductive material includes carbon nanotubes (hereinafter sometimes referred to as "CNT"), carbon black, graphite, graphene, etc. Among these, high conductivity At least one selected from carbon black and carbon nanotubes is preferable, and carbon nanotubes are more preferable, from the viewpoint of realizing properties. The carbon material-based conductive material may be of one type or a combination of two or more types.

(CNT)
The average diameter of CNTs that can be used as a carbon material-based conductive material is not particularly limited, but from the viewpoint of improving the dispersibility of CNTs, it is preferably 2 nm or more, more preferably 3 nm or more, and still more preferably 5 nm or more. From the viewpoint of improving properties, the thickness is preferably 100 nm or less, more preferably 70 nm or less, and even more preferably 50 nm or less. In the present disclosure, the average diameter of CNTs can be measured by Scanning Electron Microscopy (SEM) or Atomic Force Microscopy (AFM).

Two or more types of CNTs with different diameters may be used as CNTs that can be used as a carbon material-based conductive material in order to achieve both conductivity and dispersibility. When two or more types of CNTs having different diameters are used, the average diameter of relatively thin CNTs is preferably 2 nm or more, more preferably 3 nm or more, and still more preferably 5 nm or more, from the viewpoint of dispersibility, and From the viewpoint of conductivity, the thickness is preferably less than 30 nm, more preferably 25 nm or less, and even more preferably 20 nm or less. The average diameter of relatively thick CNTs is preferably 30 nm or more, more preferably 35 nm or more, still more preferably 40 nm or more from the viewpoint of dispersibility, and preferably 100 nm or less from the viewpoint of improving conductivity. , more preferably 70 nm or less, and still more preferably 50 nm or less.

The average length of CNTs is measured by scanning electron microscope (SEM) or atomic force microscope (AFM). In the present disclosure, the average length is not particularly limited, but from the viewpoint of improving conductivity, it is preferably 2 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, and even more preferably 30 μm or more. From the viewpoint of improving properties, the thickness is preferably 500 μm or less, more preferably 300 μm or less, still more preferably 200 μm or less, and even more preferably 120 μm or less.

In the present disclosure, CNT means an aggregate including a plurality of CNTs. The form of the CNTs used for preparing the conductive material slurry is not particularly limited. may be mixed. The CNTs may be CNTs of various layer numbers or diameters. CNTs may contain impurities (eg, catalysts and amorphous carbon) from the process in which CNTs are manufactured.

The content of impurities in CNTs is measured by a method such as thermogravimetric analysis, but in the present disclosure, the lower the better. The content of impurities in CNTs is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 10% by mass, from the viewpoint of increasing the concentration of effective CNTs. Below, it is still more preferably substantially 0% by mass.

In one or more embodiments, CNTs that can be used as a carbon material-based conductive material have a cylindrical shape by winding one sheet of graphite. SWCNT), those wound in two layers are called double-walled carbon nanotubes (DWCNT), and those wound in three or more layers are also called multi-walled carbon nanotubes (MWCNT). Single-layer, double-layer, or multilayer CNTs and mixtures thereof can be used depending on the properties required for the positive electrode coating film formed using the positive electrode paste for an electricity storage device containing the CNT slurry. The positive electrode coating film is a film-like layer obtained by coating an electrode substrate (current collector).

Examples of CNTs that can be used as carbon material-based conductive materials include Nanocyl's NC-7000 (hereafter, numerical values are average diameters of 9.5 nm), NX7100 (10 nm), and Cnano's FT6100 (9 nm) and FT-6110 (9 nm). , FT-6120(9nm), FT-7000(9nm), FT-7010(9nm), FT-7320(9nm), FT-9000(12.5nm), FT-9100(12.5nm), FT-9110(12.5 nm), FT-9200 (19 nm), FT-9220 (19 nm), Cabot Performance material (Shenzhen) HCNTs4 (4.5 nm), CNTs5 (7.5 nm), HCNTs5 (7.5 nm), GCNTs5 (7.5 nm), HCNTs10 (15nm), CNTs20 (25nm), CNTs40 (40nm), Korean CNT CTUBE170 (13.5nm), CTUBE199 (8nm), CTUBE298 (10nm), Kumho K-Nanos100P (11.5nm), LG Chem CP -1001M (12.5 nm), BT-1003M (12.5 nm), Nano Tech Port's 3003 (10 nm), 3021 (20 nm), and the like.
Examples of CNTs when using a combination of two types of CNTs include, for example, a combination of CNTs40 (40 nm) and HCNTs4 (4.5 nm) or HCNTs5 (7.5 nm) from Cabot Performance Material (Shenzhen), CNTs40 (40 nm) and GCNTs5 (7.5 nm), CNTs40 (40 nm) and Cnano FT-7010 (9 nm), CNTs40 (40 nm) and FT-9100 (12.5 nm), CNTs40 (40 nm) and LG Chem A combination with BT-1003M (12.5 nm) is included.

(Carbon black)
Various types of carbon black such as furnace black, channel black, thermal black, acetylene black (AB), and ketjen black can be used as the carbon material-based conductive material. In addition, carbon black subjected to oxidation treatment, hollow carbon, and the like, which are commonly used, can also be used. Oxidation treatment of carbon is carried out by subjecting carbon to high temperature treatment in the air, or by secondary treatment with nitric acid, nitrogen dioxide, ozone, etc., to remove phenol groups, quinone groups, carboxy groups, carbonyl groups, etc. This is a treatment for directly introducing (covalently bonding) oxygen-containing polar functional groups to the surface of carbon, and is generally performed to improve the dispersibility of carbon. However, since the conductivity of carbon generally decreases as the amount of functional groups introduced increases, it is preferable to use carbon that has not been oxidized.

The larger the specific surface area of carbon black that can be used as a carbon material-based conductive material, the greater the number of contact points between carbon black particles, which is advantageous for lowering the internal resistance of the electrode. Specifically, it is desirable to use a specific surface area (BET) determined from the nitrogen adsorption amount, preferably 20 m ² /g or more and 1500 m ² /g or less.

The primary particle size (diameter) of carbon black that can be used as a carbon material-based conductive material is preferably 5 to 1000 nm from the viewpoint of conductivity. In the present disclosure, the primary particle size of carbon black is the average of particle sizes measured with an electron microscope or the like.

Examples of carbon black that can be used as a carbon material-based conductive material include Toka Black #4300, #4400, #4500, #5500 (manufactured by Tokai Carbon Co., Ltd., Furnace Black), Printex L, etc. (manufactured by Degussa, Furnace Black ), Raven7000, 5750, 5250, 5000ULTRAIII, 5000ULTRA, etc., Conductex SC ULTRA, Conductex 975 ULTRA, etc. (manufactured by Columbian, Furnace Black), #2350, #2400B, #30050B, #3030B, #3230B, # 3350B, #3400B , # 5400B, etc. (Mitsubishi Chemical Co., Ltd., Furnes Black), MonArch1400, 1300, 900, VULCANXC -72R, BLACKPEARLS2000 (Cabot Co., Ltd., Fahnes Black), ENSACO250G, ENSACO260G, ENN SACO350G, SUPERP -LI (manufactured by Timcal), Ketjen Black EC-300J, EC-600JD (manufactured by Akzo Co., Ltd.), Denka Black, Denka Black HS-100, FX-35, Li-100, Li-250, Li-400, Li-435 (manufactured by Denka Co., Ltd., acetylene black) and the like, but are not limited to these.

(graphene)
Graphene, which can be used as a carbon material-based conductive material, generally refers to a one-atom-thick sheet of sp2 ^- bonded carbon atoms (single-layer graphene). Graphene is also used to refer to substances with morphology.

The thickness of graphene that can be used as a carbon material-based conductive material is not particularly limited, but is preferably 100 nm or less, more preferably 50 nm or less, and still more preferably 20 nm or less. The size in the direction parallel to the graphene layer is not particularly limited, but if it is too small, the conductive path per graphene will be shortened, resulting in poor conductivity due to the contact resistance between graphenes. Therefore, it is preferable that the graphene in the present disclosure is larger than a certain amount. The size in the direction parallel to the graphene layer is preferably 0.5 μm or more, more preferably 0.7 μm or more, and even more preferably 1 μm or more. Here, the size in the direction parallel to the graphene layer means the average of the maximum diameter and the minimum diameter when observed from the direction perpendicular to the plane direction of the graphene.

(Content of carbon material-based conductive material in conductive material slurry)
The content of the carbon material-based conductive material in the conductive material slurry of the present disclosure is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, from the viewpoint of improving the convenience of adjusting the concentration of the positive electrode paste. It is more preferably 1% by mass or more, and from the viewpoint of making the conductive material slurry easy to handle, it is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less.

(Content of polymer A in conductive material slurry)
The content of the polymer A in the conductive material slurry of the present disclosure is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably, from the viewpoint of improving the dispersibility of the carbon material-based conductive material. is 0.08% by mass or more, still more preferably 0.15% by mass or more, and from the viewpoint of high conductivity, preferably 2.0% by mass or less, more preferably 1.5% by mass or less, and further It is preferably 1.2% by mass or less, and still more preferably 1.0% by mass or less.

The content of the polymer A (dispersant) in the conductive material slurry of the present disclosure is preferably 0.1 mass with respect to 100 parts by mass of the carbon material-based conductive material from the viewpoint of improving the dispersibility of the carbon material-based conductive material. parts or more, more preferably 1 part by mass or more, still more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, and from the viewpoint of high conductivity, preferably 200 parts by mass or less, more preferably 150 parts by mass. It is not more than 90 parts by mass, more preferably not more than 75 parts by mass.

(Content of organic amine B2 in conductive material slurry)
The content of the organic amine B2 in the conductive material slurry of the present disclosure is preferably 0.01% by mass or more, more preferably 0, from the viewpoint of improving the dispersibility of the carbon material-based conductive material and reducing the resistance of the electricity storage device. 0.05% by mass or more, more preferably 0.1% by mass or more, still more preferably 0.2% by mass or more, and from the viewpoint of high conductivity, preferably 2.0% by mass or less, more preferably It is 1.5% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.8% by mass or less.

The content of the organic amine B2 in the conductive material slurry of the present disclosure is preferably based on 100 parts by mass of the carbon material-based conductive material from the viewpoint of improving the dispersibility of the carbon material-based conductive material and reducing the resistance of the electricity storage device. is 1 part by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more, and from the viewpoint of high conductivity, preferably 200 parts by mass or less, more It is preferably 100 parts by mass or less, more preferably 50 parts by mass or less.

(Method for producing conductive material slurry)
In one or more embodiments, the conductive material slurry of the present disclosure is obtained by mixing a mixture of the dispersant composition of the present disclosure, the carbon material-based conductive material, and the organic solvent or organic amine B2 added as necessary. It can be prepared by mixing with a disperser. As the organic solvent to be added, an organic solvent having a dielectric constant of 25.0 or more and 35.0 or less at 25° C. is preferable. things are mentioned.

Examples of the mixing and dispersing machine include at least one selected from ultrasonic homogenizers, vibration mills, jet mills, ball mills, bead mills, sand mills, roll mills, homogenizers, high-pressure homogenizers, ultrasonic devices, attritors, desolvers, and paint shakers. seeds. A part of the components of the conductive material slurry can be mixed and then mixed with the rest. good too. The state of the carbon material-based conductive material may be a dry state or a state containing a solvent. Examples of the solvent include the same organic solvent C as described above.

<Positive electrode paste for power storage device>
In one aspect of the present disclosure, a positive electrode paste for an electricity storage device (hereinafter also referred to as "positive electrode paste of the present disclosure") containing a dispersant composition of the present disclosure, a positive electrode active material, and a carbon material-based conductive material. Regarding. Preferred forms of the dispersant composition of the present disclosure in this aspect are described above. The positive electrode paste of the present disclosure, in one or more embodiments, contains a polymer A, an organic solvent C, a carbon material-based conductive material, a positive electrode active material, and optionally an additional organic solvent or organic amine B2.

Since the positive electrode paste of the present disclosure contains the dispersant composition of the present disclosure, it is possible to form a positive electrode coating film with a small resistance value.

The positive electrode paste of the present disclosure can further contain a binder in one or more embodiments.
In one or more embodiments, the positive electrode paste of the present disclosure may further contain a conductive material other than the carbon material-based conductive material. Examples of the conductive material other than the carbon material-based conductive material include conductive polymers such as polyaniline. Moreover, an additional organic solvent is included as needed.

(Positive electrode active material)
The positive electrode active material is not particularly limited as long as it is an inorganic compound, and for example, a compound having an olivine structure or a lithium transition metal composite oxide can be used. Examples of compounds having an olivine structure include compounds represented by the general formula Li _x M1 _s PO ₄ (where M1 is a 3d transition metal, 0≦x≦2, 0.8≦s≦1.2). A compound having an olivine structure may be coated with amorphous carbon or the like. Examples of the lithium transition metal composite oxide include lithium manganese oxide having a spinel structure, and general formula Li _x MO _2- δ having a layered structure (where M is a transition metal, 0.4≦x≦1.2, 0 ≤ δ ≤ 0.5), and the like. The transition metal M may contain Co, Ni or Mn. The lithium-transition metal composite oxide may further contain one or more elements selected from Al, Mn, Fe, Ni, Co, Cr, Ti, Zn, P, and B.

The content of the positive electrode active material in the positive electrode paste of the present disclosure is not particularly limited as long as it can be adjusted according to the viscosity suitable for applying the positive electrode paste to the current collector, but from the viewpoint of energy density and From the viewpoint of the stability of the positive electrode paste, it is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less. , more preferably 80% by mass or less.

There is no particular limitation on the content of the positive electrode active material in the total solid content of the positive electrode paste of the present disclosure. The content of the positive electrode active material in the total solid content of the positive electrode paste of the present disclosure may be the same as that in the total solid content of the conventionally known positive electrode paste. 0% by mass or more is preferable, and 99.9% by mass or less is preferable in order to ensure the conductivity and coating properties of the composite layer.

(Binder)
As the binder (binder resin), polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, polyacrylonitrile, etc. can be used alone or in combination. .

The content of the binder in the total solid content of the positive electrode paste of the present disclosure is preferably 0.05% by mass or more from the viewpoint of the coating properties of the composite layer and the binding property with the current collector. From the viewpoint of keeping the energy density of the device high, it is preferably 9.95% by mass or less.

(Content of polymer A in positive electrode paste)
From the viewpoint of coating film resistance, the content of polymer A in the positive electrode paste of the present disclosure is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and 2.0% by mass or less. Preferably, 1.0% by mass or less is more preferable.

(Content of organic amine B2 in positive electrode paste)
The content of the organic amine B2 of the present disclosure in the positive electrode paste of the present disclosure is preferably 0.002% by mass or more, more preferably 0, from the viewpoint of increasing the solid content concentration of the positive electrode paste and reducing the viscosity. 0.012% by mass or more, more preferably 0.02% by mass or more, and from the viewpoint of solubility in the solvent and stability of the positive electrode paste, preferably 0.2% by mass or less, more preferably 0.1% by mass % by mass or less, more preferably 0.05% by mass or less.

(Content of carbon material-based conductive material in positive electrode paste)
The content of the carbon material-based conductive material in the positive electrode paste of the present disclosure is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.05% by mass or more, from the viewpoint of the conductivity of the composite layer. It is 1% by mass or more, and from the viewpoint of maintaining a high energy density of the electricity storage device, it is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less.

In one or more embodiments, the positive electrode paste of the present disclosure includes a positive electrode active material, a conductive material slurry of the present disclosure, a binder, and an organic solvent (additional solvent) for adjusting the solid content, etc., mixed and stirred. can be made by In addition, a dispersant other than polymer A, a functional material, or the like may be added. As the organic solvent (additional solvent), an organic solvent having a dielectric constant of 25.0 or more and 35.0 or less at 25° C. is preferable. are listed. In addition, in the preparation of the positive electrode paste of the present disclosure, it is preferable to use a non-aqueous solvent as the organic solvent (additional solvent), and among them, it is more preferable to use NMP. A planetary mixer, a bead mill, a jet mill, or the like can be used for mixing and stirring, and these can also be used in combination.

The positive paste of the present disclosure can also be prepared by premixing some of all the components used to prepare the positive paste and then mixing it with the remainder. Also, each component may be added in multiple batches instead of adding the entire amount at once. As a result, the mechanical load on the stirrer can be reduced.

The solid content concentration of the positive electrode paste of the present disclosure, the amount of the positive electrode active material, the amount of the binder, the amount of the conductive material slurry, the amount of the additive component added, and the amount of the organic solvent are determined by applying the positive electrode paste to the current collector. can be adjusted according to the viscosity suitable for From the viewpoint of dryness, it is preferable that the amount of the organic solvent is small, but from the viewpoint of the uniformity of the positive electrode mixture layer and the smoothness of the surface, it is preferable that the viscosity of the positive electrode paste is not too high. On the other hand, it is preferable that the viscosity of the positive electrode paste is not too low from the viewpoint of suppressing drying and obtaining a sufficient thickness of the mixture layer (positive electrode coating film).

Although it is preferable that the positive electrode paste of the present disclosure can be adjusted to a high concentration from the viewpoint of production efficiency, a significant increase in viscosity is not preferable from the viewpoint of workability. Additives can keep the preferred viscosity range while keeping the concentration high.

The conductive material slurry and the positive electrode paste of the present disclosure may each further contain other components within a range in which the effects of the present disclosure are not hindered. Other components include, for example, antioxidants, neutralizers, antifoaming agents, preservatives, dehydrating agents, rust preventives, plasticizers, binders, and the like.

(Manufacturing method of positive electrode paste)
In one or more embodiments, the method for producing the positive electrode paste of the present disclosure includes the carbon material-based conductive material slurry of the present disclosure, a binder, a positive electrode active material, and, if necessary, an additional organic solvent or organic amine B2. can include the step of mixing the In one or more embodiments, the positive electrode paste manufacturing method of the present disclosure may further mix an additional dispersant composition of the present disclosure and an additional carbon material-based conductive material as necessary. Each component may be mixed in any order. Further, in one or more embodiments, the conductive material slurry of the present disclosure, an additional organic solvent, and a binder are mixed and dispersed until they are homogeneous, and then the positive electrode active material is mixed, and these are homogeneous. A method of obtaining a positive electrode paste by stirring until it becomes The order of addition of these components is not limited to this.

<Method for producing positive electrode coating film or positive electrode for power storage device>
In one aspect, the present disclosure relates to a method for producing a positive electrode coating film or a positive electrode for a power storage device, which is produced using the positive electrode paste of the present disclosure. The production method of this embodiment includes applying the positive electrode paste of the present disclosure to a current collector, drying and pressing the current collector. In this aspect, preferred forms of the positive electrode paste of the present disclosure are as described above. In the manufacturing method of the present disclosure, a positive electrode coating film or a positive electrode for an electric storage device can be manufactured by a conventionally known method, except for using the positive electrode paste of the present disclosure.

A positive electrode coating film or a positive electrode for an electric storage device is prepared, for example, by applying the positive electrode paste described above to a current collector such as an aluminum foil and drying it. In order to increase the density of the positive electrode coating film, compaction can also be performed using a press. A die head, a comma reverse roll, a direct roll, a gravure roll, or the like can be used for coating the positive electrode paste. Drying after coating can be carried out by heating, air flow, infrared irradiation, etc. alone or in combination. Drying after coating is performed at a temperature at which the organic solvent in the positive electrode paste cannot exist in the positive electrode paste due to the drying time. The drying temperature is not particularly limited as long as it is equal to or lower than the thermal decomposition temperature of the binder resin under the environment (atmospheric pressure or vacuum) in which the drying is performed, but is preferably equal to or higher than the boiling point of the organic solvent. The drying temperature is preferably 60° C. or more and 220° C. or less, and the drying time is preferably 10 minutes or more and 24 hours or less. The positive electrode can be pressed using a roll press machine or the like. After pressing, the positive electrode for an electricity storage device may be processed into a size to be incorporated into the electricity storage device, and then dried again under the above conditions.

<Energy storage device and its manufacturing method>
In one aspect, the present disclosure relates to an electricity storage device including the electricity storage device positive electrode obtained by the electricity storage device positive electrode manufacturing method of the present disclosure, and a manufacturing method thereof.
As the electricity storage device, in one or more embodiments, a lithium ion secondary battery, a lithium air secondary battery, a sodium ion battery, a sodium-sulfur secondary battery, a sodium-nickel chloride secondary battery, an organic radical battery, zinc -Rechargeable air batteries, solid-state batteries, etc.

The method for manufacturing an electricity storage device of the present disclosure includes steps similar to known methods for manufacturing an electricity storage device, except that the positive electrode for an electricity storage device of the present disclosure is used as a positive electrode for an electricity storage device. In the method for producing an electricity storage device of the present disclosure, for example, two electrodes (a positive electrode and a negative electrode) are superimposed with a separator interposed therebetween, a step of winding or stacking them in a battery shape, and the resulting wound body or It includes a step of putting the laminate into a battery container or a laminate container, injecting an electrolytic solution into the container, and sealing the container.

Examples and comparative examples of the present disclosure are shown below, but the present disclosure is not limited thereto.

1. Measurement method of each parameter [Measurement of weight average molecular weight]
The weight average molecular weight of the copolymer before amide modification was measured by the GPC method. Detailed conditions are as follows.
Measuring device: HLC-8320GPC (manufactured by Tosoh Corporation)
Column: α-M + α-M (manufactured by Tosoh Corporation)
Column temperature: 40°C
Detector: _Refractive index Eluent: N,N-dimethylformamide (DMF) solution of 60 mmol/L _H3PO4 and 50 mmol/L LiBr Flow rate: 1 mL/min
Standard sample used for calibration curve: Polystyrene sample solution: DMF solution containing 0.5 wt% solid content of copolymer Injection volume of sample solution: 100 µL

[Measurement of viscosity of conductive material slurry]
The viscosity (25° C.) of the conductive material slurry was measured as follows. Anton Paar's MCR302 rheometer was equipped with a parallel plate PP50, and after increasing the shear rate from 0.1 s ^-1 to 1000 s ^-1 (outward trip), it was returned from 1000 s ^-1 to 0.1 s ^-1 (return trip). , and the viscosity at a return shear rate of 1 s ^-1 was measured. The results are shown in Table 2.

[Measurement of dispersed particle size of CNT]
A conductive material slurry diluted about 50 times with NMP was placed in a glass cell, and the dispersed particle size of CNTs was measured at 25 ° C. with a particle size measuring device Zetasizer Nano-S (manufactured by Malvern Panalytical). Ta.

[Measurement of resistance value of positive electrode coating film]
The positive electrode paste was dripped onto a polyester film and applied uniformly with a 100 μm applicator. The coated polyester film was dried at 80° C. for 1 hour to obtain a positive electrode coating film having a thickness of 40 μm.
The coating film resistance value was measured at a threshold voltage of 10 V using Loresta-GP (manufactured by Mitsubishi Chemical Analytic Tech) equipped with a PSP probe. The results are shown in Table 3.

[Measurement of direct current resistance (DCR)]
In order to measure DC resistance, an electricity storage device was produced in the following procedure.
The positive electrode paste was coated on an Al foil (current collector) having a thickness of 20 μm so that the positive electrode capacity was 3 mAh/cm ² , and vacuum-dried at 100° C. for 12 hours using a vacuum dryer. An electrode material (positive electrode material) having a composite material layer formed thereon was produced. This positive electrode material was punched out and pressed into a diameter of 13 mm to obtain an electrode (positive electrode). A separator with a diameter of 19 mm and a coin-shaped metal lithium with a diameter of 15 mm and a thickness of 0.5 mm were placed on the positive electrode to prepare a 2032 type coin cell (test half cell). 1M LiPF ₆ EC/DEC (volume ratio=3/7) was used as the electrolyte.

A 3-cycle charge/discharge test was performed under the following charge/discharge conditions while the temperature of the test half-cell was controlled in a 30° C. constant temperature bath.
(Charging and discharging conditions)
30°C, 0.2C, charge 4.45V CC/CV 1/10C cutoff discharge CC 3.0V cutoff.
Then, the battery was charged at 0.2C for 2.5 hours, and the direct current resistance (DCR) was calculated from the voltage drop for 10 seconds during 0.2C to 8C discharge. The results are shown in Table 5.

2. Preparation of dispersant composition (Example 1-1)
88.0 g of a styrene/maleic anhydride copolymer (XIRAN (registered trademark) 1000 manufactured by polyscope, weight average molecular weight of 5000) and methyl isobutyl ketone (MIBK) ( 276.2 g of Fuji Film Wako Pure Chemical Industries, Ltd.) was added and stirred for a certain period of time (0.5 hours) under a nitrogen atmosphere. After adding 112.0 g of stearylamine (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) into the flask at room temperature, the temperature of the reaction solution in the flask was raised to around 72° C. and maintained for 2 hours to obtain a polymer solution. Obtained. Dispersant A-1 was obtained by volatilizing the solvent from the polymer solution, and it was mixed with N-methyl-2-pyrrolidone (NMP) to carry out a dispersant A-1 content of 20.0% by mass. A dispersant composition of Example 1-1 was obtained. Dispersant A-1 and N-methyl-2-pyrrolidone (NMP) were mixed by stirring at 50° C. for 5 hours at a rotation speed of 200 rpm.

(Example 1-2)
621.8 g of diisobutylene (manufactured by Maruzen Petrochemical Co., Ltd.) and Lutonal A-50 (manufactured by BASF, polyvinyl ethyl ether ) was charged with 3.1 g. A nitrogen atmosphere was created in the reaction vessel, and stirring was started. The reactor contents were heated to 105° C. and the temperature of the reactor contents was maintained at 105° C. thereafter until the polymerization reaction was completed. 190.0 g of liquid maleic anhydride (manufactured by Mitsui Chemicals Polyurethane Co., Ltd.) kept at 70 ° C., and perbutyl O dissolved in 23.1 g of diisobutylene as an initiator solution (polymerization initiator, manufactured by NOF Corporation, t-butyl 9.2 g of peroxy-2-ethylhexanoate (“perbutyl” is a registered trademark) was added dropwise from separate dropping funnels into the reactor over 4 hours. After 20 minutes from the completion of the dropwise addition, 1.2 g of Perbutyl O dissolved in 7.3 g of diisobutylene was added to the reaction vessel, and further aged for 2 hours and 40 minutes to complete the polymerization reaction, resulting in a solution containing the copolymer. got 800 g of ion-exchanged water was added to the reaction vessel to deposit a precipitate of the copolymer. Unreacted diisobutylene was then distilled off by steam distillation. The steam distillation was carried out by heating the reaction vessel under normal pressure until the temperature of the contents of the reaction vessel reached 100° C. and no more diisobutylene was distilled. Next, after removing water by decantation, the precipitate of the copolymer wetted with water was dried at 105° C. under reduced pressure of 100 mmHg for 24 hours to obtain a diisobutylene/maleic anhydride copolymer having a weight average molecular weight of 28,000. Coalescence a was obtained.

88.0 g of the diisobutylene/maleic anhydride copolymer a (weight average molecular weight: 28000) obtained by the above method was placed in a four-neck glass separable flask with an internal volume of 1 L, methyl isobutyl ketone (MIBK) (Fujifilm Sum 276.2 g of Kojunyaku Co., Ltd.) was added and stirred for a certain period of time (0.5 hour) under a nitrogen atmosphere. Then, after adding 112.0 g of stearylamine (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) into the flask at room temperature, the reaction solution in the flask was heated to around 72° C. and held for 2 hours to remove non-volatile matter. A 40% by weight polymer solution was obtained. The solvent is volatilized from the polymer solution to obtain dispersant A-2, which is mixed with N-methyl-2-pyrrolidone (NMP) so that the content of dispersant A-2 is 20.0% by mass. A dispersant composition of Example 1-2 was obtained. Dispersant A-2 and N-methyl-2-pyrrolidone (NMP) were mixed by stirring at 50° C. for 5 hours at a rotation speed of 200 rpm.

(Examples 1-3 to 1-7, Comparative Example 1-1)
Dispersants A-3 to A-8 shown in Table 1 below were synthesized by changing the type or amount of the amine compound used in synthesizing the dispersant. Then, in the same manner as the dispersant composition of Example 1-2, dispersant compositions of Examples 1-3 to 1-7 and Comparative Example 1-1 shown in Table 1 below were obtained.

(Example 1-8)
15.3 g of Perbutyl O (polymerization initiator, t-butylperoxy-2-ethylhexanoate, manufactured by NOF Corporation) dissolved in 23.1 g of diisobutylene (manufactured by Maruzen Petrochemical Co., Ltd.) was used as the initiator solution. A diisobutylene/maleic anhydride copolymer b having a weight-average molecular weight of 9,000 was obtained by performing the same operation as in the synthesis of the copolymer a, except that it was added.
The same procedure as in Example 1-2 was performed except that the diisobutylene/maleic anhydride copolymer b (weight average molecular weight: 9000) obtained by the above method was used instead of the above copolymer a in Example 1-2. The operation was carried out to obtain dispersant A-9 and dispersant compositions of Examples 1-8.

(Example 1-9)
17.4 g of Perbutyl O (polymerization initiator, t-butylperoxy-2-ethylhexanoate, manufactured by NOF Corporation) dissolved in 23.1 g of diisobutylene (manufactured by Maruzen Petrochemical Co., Ltd.) was used as the initiator solution. A diisobutylene/maleic anhydride copolymer c having a weight-average molecular weight of 6,000 was obtained by performing the same operation as in the synthesis of the copolymer a, except that it was added.
The same procedure as in Example 1-2 was performed except that the diisobutylene/maleic anhydride copolymer c (weight average molecular weight: 6000) obtained by the above method was used instead of the above copolymer a in Example 1-2. The operation was carried out to obtain dispersant A-10 and dispersant compositions of Examples 1-9.

(Example 1-10)
54.59 g of Isoban 04 (manufactured by Kuraray Co., Ltd., isobutylene-maleic anhydride copolymer, weight average molecular weight: 60000), tetrahydrofuran (THF) (Fujifilm Wako Pure 350.00 g of Yaku Co., Ltd.) was added and stirred for a certain period of time (0.5 hours) under a nitrogen atmosphere. Then, after adding 95.41 g of stearylamine (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) into the flask at room temperature, the reaction solution in the flask was heated to around 50° C. and held for 2 hours to obtain a polymer solution. Obtained. The solvent was volatilized from the polymer solution to obtain Dispersant A-11. This was mixed with N-methyl-2-pyrrolidone (NMP) to obtain a dispersant composition of Example 1-10 containing 0.5% by weight of dispersant A-11. Dispersant A-11 and N-methyl-2-pyrrolidone (NMP) were mixed by stirring at 50° C. for 5 hours at a rotation speed of 200 rpm.

(Example 1-11)
20.0 parts by mass of dispersant A-2, 3.7 parts by mass of 2-amino-2methyl-1-propanol (organic amine B2) in an amount capable of neutralizing dispersant A-2, and N-methyl- 76.3 parts by mass of 2-pyrrolidone (NMP) was stirred and mixed at 50° C. for 5 hours at a rotation speed of 200 rpm to obtain a dispersant composition of Example 1-11.

(Example 1-12)
20.0 parts by weight of dispersant A-2, 10.0 parts by weight of 2-amino-2methyl-1-propanol (organic amine B2), and 70.0 parts by weight of N-methyl-2-pyrrolidone (NMP) were stirred and mixed at 50° C. for 5 hours at a rotation speed of 200 rpm to obtain a dispersant composition of Example 1-12.

(Example 1-13)
20.0 parts by weight of dispersant A-2, 20.0 parts by weight of 2-amino-2methyl-1-propanol (organic amine B2), and 60.0 parts by weight of N-methyl-2-pyrrolidone (NMP) were stirred and mixed at 50° C. for 5 hours at a rotational speed of 200 rpm to obtain a dispersant composition of Example 1-13.

(Examples 1-14 to 1-18)
Examples 1-14 to 1-14 were prepared in the same manner as in Example 1-13, except that 2-amino-2methyl-1-propanol (organic amine B2) was replaced with organic amine B2 shown in Table 1 below. A dispersant composition of -18 was obtained.

(Comparative Example 1-2)
A dispersant composition of Comparative Example 1-2 was prepared in the same manner as the dispersant composition of Example 1-2 except that NMP was replaced with toluene.

(Comparative Example 1-3)
A dispersant composition of Comparative Example 1-3 was prepared in the same manner as the dispersant composition of Example 1-2 except that NMP was replaced with dimethylformamide.

(Comparative Example 1-4)
A dispersant composition of Comparative Example 4 was prepared in the same manner as the dispersant composition of Example 1-2 except that NMP was replaced with 2-propanol.

(Comparative Example 1-5)
A dispersant composition of Comparative Example 1-5 was prepared in the same manner as the dispersant composition of Example 1-2 except that NMP was replaced with ethanol.

Regarding the dispersant composition of Comparative Example 1-3, even if the mixture of dispersant A-2 and organic solvent (dimethylformamide) was stirred at 50° C. for 5 hours at a rotational speed of 200 rpm, dispersant A-2 was visually confirmed to be insoluble in the organic solvent (see Comparative Example 2-3 in Table 2). The other dispersant compositions were visually confirmed to be uniform and transparent solutions with no undissolved dispersant.

3. Preparation of conductive material slurry (Example 2-1)
MW carbon nanotubes as fibrous carbon nanostructures (manufactured by LG Chem, multi-walled carbon nanotubes BT-1003M, average diameter 12.5 nm, length 10 to 70 μm (catalog value), and the dispersant composition of Example 1-1 , and additional NMP to obtain a crude dispersion containing 1.5 parts by mass of MW carbon nanotubes (CNT), 0.30 parts by mass of a dispersant, and 98.2 parts by mass of NMP.
The obtained coarse dispersion is filled into a high-pressure homogenizer (manufactured by Mitsuyu Co., Ltd., product name "BERYU MINI") having a multistage pressure control device (multistage pressure reducer) that applies back pressure during dispersion, and is subjected to a pressure of 120 MPa. Distributed processing was performed. Specifically, while applying back pressure, a shearing force was applied to the coarse dispersion to disperse the MW carbon nanotubes, thereby obtaining the conductive material slurry of Example 2-1 as a fibrous carbon nanostructure dispersion. . The dispersion treatment was performed while circulating the dispersion by discharging it from the high-pressure homogenizer and reinjecting it into the high-pressure homogenizer, and the circulation was performed 20 times. The discharge and injection rate of the dispersion was 45 g/min.
When the viscosity of the obtained conductive material slurry of Example 2-1 was measured at a temperature of 25° C., the viscosity was 17 mPa·s.

(Examples 2-2 to 2-18, Comparative Examples 2-1 to 2-5)
Instead of the dispersant composition of Example 1-1, the dispersant compositions of Examples 1-2 to 1-18 and Comparative Examples 1-1 to 1-5 were used, respectively, and the conductive composition of Example 2-1 was used. Conductive material slurries of Examples 2-2 to 2-18 and conductive material slurries of Comparative Examples 2-1 to 2-5 were prepared in the same manner as in the preparation of material slurries. The compositions of the conductive material slurries were each as shown in Table 2.

As shown in Table 2, the conductive material slurry of the example has a significantly lower viscosity than the conductive material slurry of the comparative example, and the dispersed particle diameter of CNT is small, indicating that the dispersibility is good. .

4. Preparation of positive electrode paste (Example 3-1)
2.06 g of the conductive material slurry of Example 2-1, 1.03 g of NMP, and 1.9 g of a PVDF (8%) NMP solution (KF Polymer L #7208, manufactured by Kureha Co., Ltd.) were weighed into a 50 ml sample bottle, followed by a spatula. Stir evenly with Thereafter, 12 g of LiCoO ₂ (Cellseed, manufactured by Nippon Kagaku Kogyo Co., Ltd.) was added as a positive electrode active material, and the mixture was stirred again with a spatula until uniform. Further, the mixture was stirred for 5 minutes with a rotation/revolution mixer (AR-100, manufactured by Thinky Co., Ltd.) to obtain a positive electrode paste of Example 3-1.
The mass ratio of the positive electrode active material, the binder (PVDF), the conductive material (carbon nanotube) and the dispersant was 98.45:1.25:0.25:0.05 (in terms of solid content), and the positive electrode paste The solid content (% by mass) of was set to 71.7% by mass. The total solid content of the positive electrode paste is the total mass of the positive electrode active material, binder, conductive material and dispersant contained in the positive electrode paste.

(Examples 3-2 to 3-10, Comparative Examples 3-1 to 3-5)
Example 3-1 except that the conductive material slurries of Examples 2-2 to 2-10 and Comparative Examples 2-1 to 2-5 were used instead of the conductive material slurry of Example 2-1. Positive electrode pastes of Examples 3-2 to 3-10 and Comparative Examples 3-1 to 3-5 were prepared in the same manner.

In Table 3 below, positive electrode coating films were prepared according to the method described in [Measurement of resistance value of positive electrode coating film], and the coating film resistance was measured, and the results are shown.

As shown in Table 3, the coating resistance of the positive electrode coating film formed using the positive electrode paste of Example is higher than that of the positive electrode coating film formed using the positive electrode paste of Comparative Example 3-1. significantly lower than the resistance. In Comparative Examples 3-2 to 3-5, the dispersion of the carbon material-based conductive material was insufficient, so that the coating film resistance exceeded the upper limit of the measuring device and could not be measured.

5. Preparation of positive electrode for power storage device
(Example 4-1)
2.6 g of the conductive material slurry of Example 2-2 and acetylene black (Denka acetylene black Li-400, primary particle diameter 48 nm, specific surface area 39 m ² /g (catalog value)), which is an additional carbon material-based conductive material. 0.24 g, 0.04 g of additional power storage device electrode dispersant composition (Example 1-2), and NMP solution of PVDF (solid content 8% KF polymer L # 7208, Kureha Co., Ltd., binder solution ) was weighed into a 50 ml sample bottle and evenly stirred with a spatula. After that, 15 g of LCO (lithium cobalt oxide, manufactured by Beijing Dongsheng Co., Ltd., "GSL-5D") as a positive electrode active material and 2.4 g of NMP as an additional solvent were added, and the mixture was stirred again with a spatula until uniform. Further, the mixture was stirred for 10 minutes with a rotation/revolution mixer (AR-100, manufactured by Thinky Co., Ltd.) to obtain a positive electrode paste. The mass ratio of the positive electrode active material, binder (PVDF), conductive material (carbon nanotube), conductive material (acetylene black) and polymer A (dispersant A-2) is 96.2:1.95:0. .25:1.5:0.1 (in terms of solid content), and the solid content (mass%) of the positive electrode paste was 65 mass%. The total solid content of the positive electrode paste is the total mass of the polymer A, positive electrode active material, conductive material and binder contained in the positive electrode paste. The compounding amount (effective content, mass %) of each component in the prepared positive electrode paste is as shown in Table 4. An electricity storage device was produced using this positive electrode paste, and the results of measuring the direct current resistance (DCR) were obtained. Table 5 shows.

(Examples 4-2 to 4-9)
Positive electrode paste (Examples 4-2 to 4-4 -9) was prepared. These positive electrode pastes were used to prepare power storage devices, and the results of direct current resistance (DCR) measurement are shown in Table 5.

The DC resistance of the electric storage device including the positive electrode coating film prepared from the positive electrode pastes of Examples 4-2 to 4-9 prepared using the dispersant composition containing organic amine B2 was compared with that of the positive electrode paste of Example 4-1. is lower than the DC resistance of the electricity storage device including the positive electrode coating film prepared in . Therefore, it can be seen that when the positive electrode paste contains organic amine B2, an electricity storage device with lower resistance can be obtained.

The dispersant composition of the present disclosure has good dispersibility of the carbon material-based conductive material, and as a result, it is possible to reduce the viscosity of the carbon material-based conductive material slurry. Then, if the dispersant composition of the present disclosure is used to prepare a positive electrode paste, the viscosity of the positive electrode paste is also low, which can contribute to lower resistance of the positive electrode coating film and lower resistance of the electricity storage device.

Claims (9)

A dispersant composition for a power storage device electrode, comprising a polymer containing a repeating unit represented by the following general formula (1) and an organic solvent, wherein the organic solvent is N-methylpyrrolidone .

However, in the above general formula (1),
R ¹ is hydrogen or a methyl group;
R ² is C _n H _2n+1 , iC _n H _2n+1 , or C ₆ H ₅ , n is 1 to 10;
R ³ is C _m H _2m+1 or iC _m H _2m+1 and m is 16 to 22;
M is hydrogen, _NH4 , an alkali metal giving a salt soluble in said organic solvent or an organic ammonium soluble in said organic solvent;
Each of a and b is a molar fraction expressed as a+b=1 and satisfies 0.50≦b≦1.00. The power storage device electrode dispersant composition is further soluble in one or more of the organic solvents and has an SP value of 9.5 (cal/cm ³ ) ^1/2 or more and 14 (cal/cm ³ ) The dispersant composition for electricity storage device electrodes according to claim 1, which contains ^1/2 or less of the organic amine . The dispersant composition for an electricity storage device electrode according to claim 2, wherein the organic amine has a boiling point of 260°C or lower. The dispersant composition for an electricity storage device electrode according to claim 2, wherein the content of the organic amine is 10 parts by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the content of the polymer. A carbon material-based conductive material slurry comprising the electricity storage device electrode dispersant composition according to any one of claims 1 to 4 and a carbon material-based conductive material, wherein the organic material contained in the carbon material-based conductive material slurry A carbon material-based conductive material slurry in which the dielectric constant at 25° C. of the solvent is 25.0 or more and 35.0 or less. The carbon material-based conductive material slurry according to claim 5 , wherein the carbon material-based conductive material is at least one selected from carbon black and carbon nanotubes. A positive electrode paste for an electrical storage device, comprising the dispersant composition for an electrical storage device electrode according to any one of claims 1 to 4 , a positive electrode active material, and a carbon material-based conductive material, the positive electrode paste being included in the positive electrode paste for an electrical storage device. A positive electrode paste for an electricity storage device, wherein the organic solvent contained therein is N-methylpyrrolidone . A method for producing a positive electrode for an electric storage device using the positive electrode paste for an electric storage device according to claim 7 . A method for producing an electricity storage device using the positive electrode for an electricity storage device produced by the production method according to claim 8 .