JPH11224669A - Binder for nickel-hydrogen battery electrode and nickel-hydrogen battery electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide high conductivity, excellent electrolyte resistance and a good binding property by polymerizing and containing two kinds of specific (meta)acrylic acid alkyl ester, ethylene unsaturated carboxylic acid and a specific quantity of another monomer copolymerizable with them as required at specific ratios under the existence of a specific quantity of organo-polysiloxane. SOLUTION: Polysiloxane 1-90 pts.wt. and monomer components 99-10 pts.wt. in total are polymerized. The monomers are constituted of (meta)acrylic acid alkyl ester 1-70 wt.% having the carbon number 1-3 of the alkyl group, (meta) acrylic acid alkyl ester unit 25-97 wt.% having the carbon number 4-10 of the alkyl group, ethylene unsaturated carboxylic acid unit, and another monomer unit copolymerizable with them as required at 100 wt.% in total. The organopolysiloxane having a cyclic structure is preferably used, and methyl ester, ethyl ester or n-butyl ester is used for the (meta)acrylic acid ester.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a secondary battery electrode excellent in charge / discharge cycle characteristics, rate characteristics, and high capacity, and more particularly, to a nickel hydrogen battery electrode in which an electrode active material is held on a current collector. The present invention relates to a novel battery electrode binder.

[0002]

2. Description of the Related Art In recent years, the size and weight of electronic devices have been remarkably reduced, and technical progress in the electronic device industry has been remarkable, and demands for high energy density, safety and the like in battery technology have been increasing. Since conventional nickel-cadmium batteries cannot satisfy such demands, nickel-metal hydride batteries and lithium-ion batteries using a hydrogen storage alloy instead of cadmium for the negative electrode have attracted attention. Nickel-metal hydride batteries are compatible and similar to nickel-cadmium batteries, and can replace devices that currently use nickel-cadmium batteries. It also has the features of high energy density, high storage stability, small size and light weight. The battery electrode binder is used for the purpose of fixing the electrode active material to the current collector. Nickel-metal hydride batteries easily absorb and release hydrogen ions, leading to higher capacity and longer life.To satisfy these requirements, the binder requires a good binding property between the electrode active material and the current collector. And that the hydrogen ions in the electrolytic solution can be freely moved without resistance as much as possible, and that the volume does not change due to the electrolytic solution or charge / discharge. In addition, in recent years, the transition from analog to digital communication devices has progressed, and there is a demand for high-rate discharge performance in a wide temperature range as a required performance of batteries for communication devices. However, there remains a problem that nickel-metal hydride batteries are inferior to nickel-cadmium batteries in high-rate discharge performance at low temperatures.
However, conventional binders have a remarkable effect on the electrode active material, and it has been difficult to satisfy all of the above conditions.

[0003]

According to the present invention, mainly in a nickel-metal hydride battery, the effect on the electrode active material is small, the high conductivity is maintained, the electrolyte resistance is excellent, and the binding property with the current collector is improved. To achieve the charge / discharge cycle characteristics, rate characteristics, and high capacity of the battery.

[0004]

That is, the present invention relates to a method for preparing (a-
1) 1 to 70% by weight of (meth) acrylic acid alkyl ester having 1 to 3 carbon atoms in the alkyl group, and 25 to 25% of (a-2) (meth) acrylic acid alkyl ester unit having 4 to 10 carbon atoms in the alkyl group. 97% by weight, (b) ethylenically unsaturated carboxylic acid and, if necessary, (c) other monomer copolymerizable therewith [provided that (a-1) + (a-2) + (b) + (C) =
99 to 10 parts by weight [100% by weight] [provided that organopolysiloxane + monomer component = 10
[0 part by weight], a binder for a nickel-metal hydride battery electrode, and a binder for a nickel-hydrogen battery electrode, comprising a polyorganosiloxane-based polymer (hereinafter, referred to as a specific polymer) obtained by polymerizing the same. It is intended to provide a nickel-metal hydride battery electrode characterized by the following.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. Organopolysiloxane The organopolysiloxane used in the present invention is obtained by condensing an organosiloxane. As the organosiloxane, those having a linear structure, a branched structure, and a cyclic structure can be used, but those having a cyclic structure are particularly preferable, and compounds represented by the following general formula (1) are particularly preferable. . R ¹ _m SiO _{(4-m) / 2} (1) (wherein, R ¹ is a substituted or unsubstituted monovalent alkyl group,
A vinyl group or a phenyl group, and m represents an integer of 0 to 3. In the general formula (1), R ¹ represents, for example, a methyl group, an ethyl group, a propyl group, a vinyl group, a phenyl group,
And groups obtained by substituting them with a halogen atom or a cyano group. Specific examples of the organosiloxane represented by the general formula (1) include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, and trimethyltriphenylcyclotrisiloxane. be able to. In addition,
This organosiloxane has been condensed (polycondensed) in advance, and has a polystyrene equivalent weight average molecular weight of 500, for example.
Polyorganosiloxane of about 100,000 may be used. When the organosiloxane is condensed in advance and is a polyorganosiloxane, the molecular chain ends thereof are blocked with, for example, a hydroxyl group, an alkoxy group, a trimethylsilyl group, a dimethylvinylsilyl group, a methylphenylvinylsilyl group, a methyldiphenylsilyl group, or the like. It may be.

In the present invention, it is preferable that the organopolysiloxane is co-condensed with the above-mentioned organosiloxane with a graft crosslinking agent. By using the graft crossing agent, a polymer having a high graft ratio can be obtained, and a binder for a battery electrode which is more excellent in the properties aimed at by the present invention can be obtained. Examples of the graft-crosslinking agent include the following compounds. A compound having both an unsaturated group represented by the following formula (2-1) and an alkoxysilyl group. ^{_{H 2 = C (R 2)}} - (CH 2) n -Ar ··· (2-1) ( wherein, R ² is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, Ar is a phenyl group, n represents It represents an integer of 0 to 12.) A compound represented by the following formula (2-2). _{^{R 3 p SiO (3-P}} ) / 2 ··· (2-2) ( wherein, R ³ is a vinyl group or allyl group, p is an integer of 0 to 2.) The following formula (2-3) A compound represented by the formula: HSR ⁴ SiR ⁵ _q O _{(3-q) / 2} (2-3) (wherein, R ⁴ is a divalent or trivalent aliphatic saturated hydrocarbon group having 1 to 18 carbon atoms, and R ⁵ is It is a monovalent hydrocarbon group having 1 to 6 carbon atoms which does not contain an aliphatic unsaturated group, and q represents an integer of 0 to 2.) A compound represented by the following formula (2-4). _{CH 2 = C (CH 3)} -COO- (CH 2) r SiR 6 s O (3 _{over s) / 2 ··· (2-4)} ( wherein, R ⁶ is a hydrogen atom, a methyl group, an ethyl group , A propyl group or a phenyl group, r represents an integer of 0 to 6, and s represents an integer of 0 to 2.)

In the above formula (2-1), R ² is
A hydrogen atom or an alkyl group having 1 to 6 carbon atoms is mentioned, but a hydrogen atom or an alkyl group having 1 to 2 carbon atoms is preferable, and a hydrogen atom or a methyl group is more preferable. Further, n is an integer of 0 to 12, and more preferably 0. As the compounds shown above, p-vinylphenylmethyldimethoxysilane, 2- (m-vinylphenyl) ethylmethyldimethoxysilane, 1- (m-
(Vinylphenyl) methyldimethylisopropoxysilane, 2- (p-vinylphenyl) ethylmethyldimethoxysilane, 3- (p-vinylphenoxy) propylmethyldimethoxysilane, 3- (p-vinylbenzoyloxy) propylmethyldimethoxysilane, 1- (O-vinylphenyl) -1,1,2-trimethyl-2,2, -dimethoxydisilane, 1- (P-vinylphenyl) -1,
1, -diphenyl-3-ethyl-3,3, -diethoxydisilane, m-vinylphenyl- [3- (triethoxysilyl) propyl] diphenylsilane, [3- (p-isopropenylbenzoylamino) propyl] phenyl Compounds such as dipropoxysilane and mixtures thereof can be mentioned. Of these, p-vinylphenylmethyldimethoxysilane, 2- (p-vinylphenyl) ethylmethyldimethoxysilane, and 3- (p-vinylbenzoyloxy) propylmethyldimethoxysilane are preferred, and p-vinylphenylmethyl is particularly preferred. The use of dimethoxysilane is preferred. Examples of the compounds shown above include vinylmethyldimethoxysilane, tetravinyltetramethylcyclotetrasiloxane, and allylmethyldimethoxysilane. Examples of the compounds shown above include 3-mercaptopropylmethyldimethoxysilane. Examples of the compounds shown above include 3-methacryloxylpropylmethyldimethoxysilane.
Among these grafting agents, particularly preferred are:
These are the compounds shown above. The proportion of these grafting agents used is 20% by weight or less, preferably 0.1 to 1%, based on the total amount of the above-mentioned organosiloxane components.
0% by weight, more preferably 0.5 to 5% by weight.
When the proportion of the graft-linking agent exceeds 20% by weight, the graft ratio increases, but as the proportion of the graft-linking agent increases, the polymer becomes low in molecular weight, and as a result, a sufficient binder can be obtained.
Performance may not be obtained.

The organopolysiloxane used in the present invention is obtained by shear-mixing the above-mentioned organosiloxane and, if necessary, a graft-linking agent with a homomixer or the like in the presence of an emulsifier (surfactant) and water. It can be produced by condensation. In the present invention, the organopolysiloxane is used as an aqueous dispersion. Here, the emulsifier functions not only as an emulsifier for the organosiloxane but also as a condensation initiator. Examples of the emulsifier that can be used in the present invention include anionic surfactants such as unsaturated aliphatic sulfonic acids, hydroxylated aliphatic sulfonic acids, aliphatic substituted benzenesulfonic acids, and aliphatic hydrogen sulfates. Specifically, tetradecenesulfonic acid, hydroxytetradecanesulfonic acid, hexylbenzenesulfonic acid, octylbenzenesulfonic acid, dodecylbenzenesulfonic acid, cetylbenzenesulfonic acid, octyl sulfate, lauryl sulfate, oleyl sulfate, cetyl sulfate, etc. Can be mentioned. Further, in the present invention, other anionic surfactants and nonionic surfactants may be used in combination with the above anionic surfactant before or after emulsion polymerization, as long as the object of the present invention is not impaired. . The amount of the emulsifier used in the synthesis of the organopolysiloxane is usually 0.1 to 5% by weight, preferably 0.3 to 3% by weight, based on the total amount of the organosiloxane and the grafting agent. In addition, the amount of water used is 10% of the total amount of the organosiloxane and the graft crosslinking agent component.
0 parts by weight, usually 100 to 500 parts by weight, especially 2
The content is preferably in the range of 5 to 10 parts by weight.
The temperature is preferably set to 0 ° C. The weight average molecular weight in terms of polystyrene of the organopolysiloxane used in the present invention is preferably 30,000 to 1,000,000, and more preferably 50,000 to 300,000. If the weight average molecular weight in terms of polystyrene is less than 30,000, the strength of the obtained coating film may be insufficient, while if it exceeds 1,000,000, the adhesion of the coating film may decrease.

Monomer Component As the monomer component used in the synthesis of the specific polymer, two or more alkyl (meth) acrylates having alkyl groups having different carbon numbers are used. The alkyl group has 1 carbon atom
To 3 alkyl (meth) acrylates ((a-
Examples of the 1) component) include methyl (meth) acrylate, ethyl (meth) acrylate, and n- (meth) acrylate.
-Propyl, i-propyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate and the like. These compounds can be used alone or in combination of two or more. Examples of the alkyl (meth) acrylate having 4 to 10 carbon atoms in the alkyl group (component (a-2)) include n-butyl (meth) acrylate, i-butyl (meth) acrylate, and (meth) acrylate. ) N-amyl acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, 2-hexyl (meth) acrylate, octyl (meth) acrylate, i-nonyl (meth) acrylate, (meth) ) Decyl acrylate and the like. These compounds can be used alone or in combination of two or more. (A-1) The alkyl ester of (meth) acrylic acid having 1 to 3 carbon atoms in the alkyl group increases the swelling ratio of the obtained specific polymer in a dried coating film with respect to the electrolyte, and provides the specific polymer with elasticity, strength, It is an essential component for providing adhesive strength, and its compounding ratio is 1 to 70% by weight, preferably 3 to 55% by weight, more preferably 5 to 5% by weight based on the whole monomer component.
50% by weight. When the blending ratio of the component (a-1) is less than 1% by weight, the dried coating film becomes sticky, and the coating film strength is reduced, so that the obtained battery electrode binder has a binding property with a current collector, and an electrolytic solution resistance. Inferior to On the other hand, if it exceeds 70% by weight, the dried coating film becomes too hard, and the active material is detached from the current collector. (A-2) The alkyl (meth) acrylate having 4 to 10 carbon atoms in the alkyl group is an essential component for imparting elasticity, strength, and adhesion to the specific polymer obtained, and the compounding ratio thereof is as follows. , 25-97% by weight, preferably 30-95% by weight, more preferably 3% by weight, based on the total monomer components.
3 to 91% by weight. (A-2) The mixing ratio of the component is 2
If the amount is less than 5% by weight, the adhesion and elasticity of the dried coating film are poor. On the other hand, if it exceeds 97% by weight, the stability of the polymerization system is inferior, the dried film is sticky, and the adhesion, strength and the like are also reduced. Absent.

(B) The ethylenically unsaturated carboxylic acid includes, for example, acrylic acid, (meth) acrylic acid, itaconic acid, fumaric acid, maleic acid and the like, and preferably (meth) acrylic acid. These (b) ethylenically unsaturated carboxylic acids are essential components for maintaining the balance of stability, water resistance, and electrolyte resistance of the obtained specific polymer at a high level. Alternatively, two or more types can be used in combination. The blending ratio of the component (b)
Usually, 0.5 to 15% by weight based on the whole monomer components,
Preferably from 2 to 13% by weight, more preferably from 3 to 10% by weight.
% By weight. If the compounding ratio is less than 0.5% by weight, the obtained binder for a battery electrode has poor binding properties with a current collector,
Binder performance may be poor, while 15
If the content is more than 10% by weight, the electrolyte resistance and the storage stability may be poor.

Further, (c) other monomers copolymerizable therewith include, for example, (meth) acrylonitrile,
vinyl cyanide compounds such as α-chloroacrylonitrile; 1,3-butadiene, isoprene, 2-chloro-
Aliphatic conjugated dienes such as 1,3-butadiene; aromatic vinyl compounds such as styrene, α-methylstyrene and vinyltoluene; alkyl amides of ethylenically unsaturated carboxylic acids such as (meth) acrylamide and N-methylolacrylamide; Carboxylic acid vinyl esters such as vinyl and vinyl propionate; acid anhydrides, monoalkyl esters and monoamides of ethylenically unsaturated dicarboxylic acids; ethylenically unsaturated esters such as aminoethyl acrylate, dimethylaminoethyl acrylate and butylaminoethyl acrylate Aminoalkyl esters of carboxylic acids; aminoethylamides of ethylenically unsaturated carboxylic acids such as aminoethylacrylamide, dimethylaminomethylmethacrylamide, methylaminopropylmethacrylamide; And the like can be mentioned unsaturated aliphatic glycidyl esters such as Le (meth) acrylate, preferably acrylonitrile, (meth) acrylonitrile, 1,3-butadiene, styrene, alpha-methyl styrene and the like. These other copolymerizable monomers (c) may be used alone or in combination of two or more. (C) The other copolymerizable monomer is used in a proportion of preferably 60% by weight or less in the monomer component. 60% by weight
Exceeding this is not preferred because of problems such as a decrease in film forming properties, discoloration after film formation, and shrinkage of the coating film.

Production of Specific Polymer The specific polymer used in the present invention is preferably produced by emulsion polymerization of a monomer component in the presence of the aqueous dispersion of an organopolysiloxane. The charged composition when the monomer component is polymerized in the presence of the aqueous dispersion of the organopolysiloxane is such that the organopolysiloxane component (in terms of solid content) is 1 to 90 parts by weight, preferably 3 to 50 parts by weight,
More preferably, it is 5 to 30 parts by weight, and the monomer component is 99 to 10 parts by weight, preferably 97 to 50 parts by weight, more preferably 95 to 70 parts by weight [however, organopolysiloxane + monomer component = 100 parts by weight]. Here, if the amount of the organopolysiloxane is less than 1 part by weight, sufficient adhesion, electrolytic solution resistance, and water resistance of the obtained battery electrode binder cannot be obtained. High strength cannot be obtained, and the film formability also deteriorates.

Binder for nickel-metal hydride battery electrode The binder for a nickel-metal hydride battery electrode of the present invention can be used by dispersing the specific polymer obtained as described above in water or an organic solvent. Dispersion particle diameter when the specific polymer is dispersed in water, usually 0.01 ~ 2.0μ
m, preferably 0.1 to 0.6 μm. Examples of the organic solvent in which the specific polymer can be dispersed and used include, for example, N-methylpyrrolidone, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,1 2-trichloroethane, 1,1,
1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane, pentachloroethane, hexachloroethane, 1,1-dichloroethylene, 1,2-dichloroethylene, trichloroethylene, tetrachloroethylene, chlorobenzene, o-dichlorobenzene, m-di Halogenated hydrocarbon solvents such as chlorobenzene, p-dichlorobenzene, 1,2,4-trichlorobenzene and trichloromethylbenzene; dioxane, anisole, tetrahydrofuran, tetrahydropyran, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol Dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Ether solvents such as ethylene glycol monopropyl ether, diethylene glycol monobutyl ether, and triethylene glycol monomethyl ether; cyclohexanone, 2-acetylcyclohexanone, 2-methylcyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone, cycloheptanone, 1-decalone , 2-decalone, 2,4-dimethyl-3-pentanone, 4,4-dimethyl-2-pentanone, 2-methyl-3-hexanone, 5-methyl-2-
Hexanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-methyl-3-heptanone, 5-methyl-
3-heptanone, 2,6-dimethyl-4-heptanone,
2-octanone, 3-octanone, 2-nonanone, 3-
Ketone solvents such as nonanone, 5-nonanone, 2-decanone, 3-decanone, and 4-decanone; aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and cumene; N-methyl-2-pyrrolidone; -Acetyl-2-pyrrolidone, N-benzyl-2-pyrrolidone, N-methyl-3-pyrrolidone, N-acetyl-3-
Pyrrolidone, N-benzyl-3-pyrrolidone, formamide, N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, Amide solvents such as N-methylpropionamide; aprotic polar solvents such as dimethyl sulfoxide; 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-propoxyethyl acetate, 2-butoxyethyl acetate;
Examples thereof include acetate solvents such as 2-phenoxyethyl acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monopropyl ether acetate, and diethylene glycol monobutyl ether acetate. These organic solvents can be used alone or in combination of two or more. The binder for a battery electrode of the present invention can be used at any pH. However, in order to maintain the storage stability of the polyorganosiloxane-based polymer, the pH is adjusted using an alkaline compound.
Can be adjusted. Examples of the alkaline compound include potassium hydroxide, sodium hydroxide, aqueous ammonia, lithium hydroxide, and ethanolamine. Of these, potassium hydroxide is preferably used. Further, the binder for a battery electrode of the present invention may optionally contain a thickener in an amount of 1 to 200 parts by weight based on 100 parts by weight of the specific polymer.
You may use a weight part. As the thickener, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol,
Polyacrylic acid (salt), oxidized starch, phosphorylated starch, casein and the like are included. The solid content concentration of the battery electrode binder of the present invention is not particularly limited, but is usually 20 to 65% by weight, preferably 35 to 60% by weight. Further, a film having a thickness of 0.5 mm was formed using the binder for a battery electrode of the present invention, and was subjected to JIS K6301-
The maximum elongation of the film by a tensile test according to No. 3 is preferably 150 to 1000%, more preferably 250 to 700%. When the film elongation is less than 150%, the adhesive strength and flexibility of the electrode may be lacked. May rise and become unusable. General methods such as adjusting the polymerization temperature during the production of a specific polymer, adjusting the amount of the polymerization initiator, adjusting the polymerization conversion, adjusting the amount of the chain transfer agent, adjusting the glass transition point, and the like are used for adjusting the film elongation. Used.

Nickel-Metal Hydride Battery Electrode The battery electrode binder of the present invention can be blended with an electrode material such as an electrode active material to form a battery electrode composition. In the case of forming a battery electrode, the composition for a battery electrode may be formed together with a current collector, or an aluminum foil, a copper foil, or the like may be used as a current collector, and the composition for a battery electrode may be applied thereto and used. You can also. Preferably, the composition is obtained by applying a slurry-like composition for a battery electrode to a current collector, heating and drying. As a method for applying the composition for a battery electrode, any method such as a slit coater method, a reverse roll method, a comma bar method, a gravure method, and an air knife method can be used. A wind dryer, an infrared heater, a far infrared heater and the like can be used. The drying temperature is usually 130 ° C to 200 ° C.
It is preferable to carry out at a temperature of ° C. The battery electrode binder of the present invention has a solid content of 0.1 to 100 parts by weight of the electrode active material.
20 parts by weight, preferably 0.5 to 10 parts by weight are blended. If the amount of the binder for the battery electrode is less than 0.1 part by weight, good adhesive strength cannot be obtained, and if it exceeds 20 parts by weight, the overvoltage is significantly increased and adversely affects the battery characteristics.

As the electrode active material in the nickel-metal hydride battery electrode of the present invention, nickel hydroxide powder is generally used as the positive electrode active material, and hydrogen storage alloy powder is used as the negative electrode active material. As the hydrogen storage alloy, an alloy obtained by replacing a part of Ni with Mn, Al, Co, or the like based on MmNi ₅ is preferably used. Here, Mm represents a misch metal which is a mixture of rare earth elements. The size of the powder used as the electrode active material is a powder that has passed through 100 mesh, and the average particle size is a decrease in current efficiency, a decrease in the stability of the slurry, and a resistance between particles in the obtained electrode coating film. Due to problems such as an increase in the thickness, the thickness is preferably about 3 to 400 μm. In general, the electrode active material is provided with carbon fluoride, graphite, vapor-grown carbon fiber and / or its crushed material, PAN-based carbon fiber and / or its crushed material, and pitch-based material for the purpose of imparting conductivity. Carbon material such as carbon fiber and / or its crushed material, conductive powder such as carbon powder, carbon nickel powder, cobalt powder and copper powder, conductive polymer such as polyacetylene and poly-p-phenylene, tin oxide and fluorine And an amorphous compound composed of such a compound. However, they are not particularly limited to these. The composition for a battery electrode may further include, if necessary, a dispersant such as sodium hexametaphosphate, sodium tripolyphosphate, sodium pyrophosphate, and sodium polyacrylate, and a nonionic or anionic interface as a latex stabilizer. Additives such as activators may be added. The current collector used for the battery electrode of the present invention has a thickness of 40
It is a core plate having a thickness of about 170 μm and is preferably porous, and examples thereof include Ni mesh, punched Ni, and Ni-plated punched metal. At this time, the opening ratio of the metal core plate is usually 30 to 60%.

When assembling a nickel-metal hydride battery using the battery electrode of the present invention, the electrolyte is usually potassium hydroxide of 5 N or more, or sodium hydroxide and / or lithium hydroxide added to potassium hydroxide. Mixed solution is used. Further, if necessary, a battery is configured using components such as a separator, a current collector, a terminal, and an insulating plate. Further, the structure of the battery is not particularly limited, but a positive electrode, a negative electrode, a paper type battery having a single-layer or multiple-layer separator as needed, or a positive electrode, a negative electrode, and a roll of the separator if necessary. Examples of the form include a cylindrical battery and a rectangular battery wound in a shape. The battery electrode manufactured using the battery electrode binder of the present invention can be suitably used for AV equipment, OA equipment, communication equipment, and even electric vehicles.

[0017]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these embodiments. In this example, unless otherwise specified, “parts” indicates parts by weight. Example 1 (1) p-vinylphenylmethyldimethoxysilane
5 parts and octamethylcyclotetrasiloxane
5 parts were mixed, and this was mixed with α-olefin sulfonic acid (RC
H = CH (CH ₂ ) _n SO ₃ Na about 75% by weight, RCH
₂ CH (OH) (CH ₂ ) mSO ₃ Na (a mixture of about 25% by weight) was placed in 300 parts of distilled water in which 2.0 parts were dissolved.
The mixture was stirred for 3 minutes with a homomixer and emulsified and dispersed. This mixed solution was transferred to a separable flask equipped with a condenser, a nitrogen inlet, and a stirrer.
The condensation was completed by heating at 0 ° C. for 6 hours and cooling at 5 ° C. for 24 hours. The resulting aqueous dispersion of organopolysiloxane was neutralized to pH 7 using an aqueous sodium carbonate solution. (2) 100 parts by weight (solid content) of an organopolysiloxane aqueous dispersion, 70 parts of ion-exchanged water, and 0.3 part of ammonium persulfate were charged into a separable flask equipped with a condenser, a nitrogen inlet, and a stirrer. The gas phase was replaced with nitrogen gas for 15 minutes, and the temperature was raised to 80 ° C. (3) On the other hand, in another container, 5 parts by weight of methyl methacrylate,
90 parts by weight of n-butyl acrylate, methacrylic acid 3
Parts by weight and 2 parts by weight of N-methylolacrylamide were mixed and added dropwise to the aqueous dispersion of organopolysiloxane (2) over 3 hours. During the dropwise addition, the reaction was carried out at 80 ° C. while introducing nitrogen gas. After the completion of the dropwise addition, the mixture was further stirred at 85 ° C. for 2 hours to terminate the reaction. Thereafter, the mixture was cooled to 25 ° C. and adjusted to pH 7 with potassium hydroxide to obtain an aqueous dispersion of the specific polymer A.

Examples 2 to 5 In the same manner as in Example 1 except that the amount of the organopolysiloxane used and the composition of the monomer components were as shown in Table 1, the specific polymers BE to E were prepared. An aqueous dispersion was obtained. Comparative Example 1 70 parts of ion-exchanged water and 0.3 parts of ammonium persulfate were charged into a separable flask equipped with a condenser, a nitrogen inlet, and a stirrer, and the gas phase was replaced with nitrogen gas for 15 minutes. The temperature rose. On the other hand, the components shown in Table 1 were mixed in another container, and added dropwise to the flask over 3 hours. During the dropwise addition, the reaction was carried out at 80 ° C. while introducing nitrogen gas. After the completion of the dropwise addition, the mixture was further stirred at 85 ° C. for 2 hours to terminate the reaction. Thereafter, the mixture was cooled to 25 ° C. and adjusted to pH 7 with potassium hydroxide to obtain an acrylic emulsion (polymer a). Comparative Example 2 70 parts of ion-exchanged water and 0.3 part of potassium persulfate were charged into an autoclave equipped with a stirrer, the gas phase was replaced with nitrogen gas for 15 minutes, and the temperature was raised to 80 ° C. On the other hand, the components shown in Table 1 were mixed in a separate container and added dropwise to the autoclave over 15 hours. During the dropwise addition, the reaction was carried out at 80 ° C. After the completion of the dropwise addition, the mixture was further stirred at 85 ° C. for 5 hours to terminate the reaction. After cooling to 25 ° C., the pH was adjusted to 7 with potassium hydroxide, and then steam was introduced to remove residual monomers, and then concentrated to obtain a styrene-butadiene copolymer latex (polymer b). .

[0019]

[Table 1] (Unit: parts by weight) The abbreviations of the monomers in Table 1 are as follows:
The following compounds are shown. MMA = methyl methacrylate ((a-1) component) EMA = ethyl methacrylate ((a-1) component) BA = butyl acrylate ((a-2) component) MAA = methacrylic acid ((b) component) MAN = Methacrylonitrile (component (c)) NMAM = N-methylolacrylamide (component (c)) ST = styrene (component (c)) BD = butadiene (component (c))

Example 6 (1) Preparation of composition for battery electrode (for positive electrode) A mixed powder comprising 100 parts by weight of nickel hydroxide, 3 parts by weight of nickel powder and 1 part by weight of cobalt powder, Example 2
1 part by weight of the specific polymer A obtained in 1 above as a solid content and 1 part by weight of an aqueous carboxymethyl cellulose solution as a thickener were kneaded to prepare a composition A for a battery electrode. (2) Preparation of composition for battery electrode (for negative electrode) Hydrogen storage alloy having an average particle diameter of 100 μm (La: 0.99% by weight, Ni: 3.41% by weight, Co: 1.2% by weight, M
n: 0.1% by weight, Al: 0.29% by weight) 100 parts by weight, specific surface area 100 m ² / g, Ketchan black 10
1 part by weight of the specific polymer A obtained in Example 1 in solid content
1 part by weight of carboxymethylcellulose as a thickener and 1 part by weight of a solid content was kneaded to obtain a composition B for a battery electrode.
Was prepared.

(3) Preparation and Evaluation of Positive Electrode Sheet The composition A for a battery electrode obtained in (1) was applied to a current collector made of foamed nickel at a thickness of 400 g / m ² ,
After drying at 0 ° C. for 20 minutes and pressure bonding, a positive electrode sheet having a thickness of 200 μm was obtained. An adhesive tape was attached to the obtained positive electrode sheet, and after peeling off, the state of the applied film adhered to the adhesive surface of the tape was observed. As a result, the applied film hardly adhered. (4) Preparation and Evaluation of Negative Electrode Sheet The composition B for a battery electrode obtained in (2) having a thickness of 400 g / m ² was obtained by using a Ni-plated punching metal having a porosity of 50% and a thickness of 60 μm as a current collector. Coated at 150 ℃
For 20 minutes, and pressure-bonded to obtain a negative electrode sheet having a thickness of 200 μm. An adhesive tape was attached to the obtained negative electrode sheet, and after peeling off, the state of the applied film adhered to the adhesive surface of the tape was observed, and the binding property was evaluated by the following five-point method. Table 2 shows the results. 5 points: when the coating film hardly adheres to the adhesive surface 4 points: when the coating film adheres to 70 to 90% of the surface area of the adhesive surface 3 points: when the coating film is 40 to 70% of the surface area of the adhesive surface 2 points: 10 to 40% of the surface area of the adhesive surface has a coating film 1 point: The coating film has adhered to almost the entire adhesive surface

(5) Evaluation of conductivity A 100-μm-thick PET film was applied to a composition B for battery electrodes.
400 g / m^TwoApply at 150 ° C for 10 minutes
After drying, a coating film having a thickness of 120 μm was obtained. Using this,
Electric resistance was measured by a four-terminal method. Table 2 shows the results. (6) Electrolyte resistance  The negative electrode sheet obtained in the above (4) was treated with 6N potassium hydroxide.
Current for 24 hours at room temperature to collect electricity
By observing the peeling of the coating film from the material, the electrolyte resistance was evaluated as follows.
It was evaluated by the point method. Table 2 shows the results. 5 points: When there is almost no change 4 points: The coating film of 70 to 90% of the current collector surface area was peeled off
Case 3 points: The coating film of 40 to 70% of the current collector surface area was peeled off
Case 2 points: 10 to 40% of the coated surface of the current collector was peeled off
Case 1 point: When the coating film is almost completely peeled off

(7) Production and evaluation of nickel-metal hydride battery  The above positive electrode sheet and negative electrode sheet were 0.9 cm × 5.5.
cm, and welded Ni lead wires to each,
Separator using 6N potassium hydroxide aqueous solution as electrolyte
Using non-woven polypropylene fabric as nickel
The battery was assembled. Charge this battery to 2.0V,
Repeat the cycle of discharging to 1.0 V at 100 mA
Then, the capacity retention was measured. Also charged to 2.0V
The cell was stored at 70 ° C for 30 days, and the capacity reduction rate was measured.
Was. Table 3 shows the results.

Examples 7 to 10 and Comparative Examples 3 to 6 In the same manner as in Evaluation Example 1 except that the polymers used for the positive electrode and the negative electrode had the compositions shown in Table 2, the binding properties of the positive electrode and the negative electrode were determined.
The conductivity, electrolyte resistance, capacity preservation rate and capacity reduction rate were measured. The results are shown in Tables 3 and 4.

[0025]

[Table 2] The number of parts of the polymer in Table 2 is parts by weight on a solid basis. The symbols a to c of the polymers indicate the following polymers. A: Polytetrafluoroethylene i: Polyvinylidene fluoride C: Polyvinyl alcohol

[0026]

[Table 3]

Examples 6 to 10 are the results of the binding property, conductivity, resistance to electrolytic solution, capacity storage rate, and storage stability of the battery electrode using the battery electrode binder of the present invention. Good conductivity, conductivity and resistance to electrolytes, little capacity degradation,
Excellent cycle characteristics. On the other hand, Comparative Examples 3 to 6
Are the results of the binding, conductivity, electrolyte resistance, capacity storage rate, and storage stability of a battery using a polymer other than the specific polymer as the battery electrode binder. Comparative Example 3 is an example in which polytetrafluoroethylene was used as the battery electrode binder for the positive electrode and a polyvinylidene fluoride-based polymer was used as the battery electrode binder for the negative electrode, and the binding properties were poor and the battery characteristics were poor.
Comparative Example 4 is an example in which polytetrafluoroethylene was used as the battery electrode binder for the positive electrode and acrylic emulsion was used for the binder for the battery electrode as the negative electrode.
Poor in both electrolyte resistance and battery characteristics. In Comparative Example 5, polytetrafluoroethylene was used as the binder for the battery electrode of the positive electrode,
This is an example in which a styrene-butadiene copolymer latex is used as a binder for a battery electrode of a negative electrode, and is inferior in binding properties.
Comparative Example 6 is an example in which polytetrafluoroethylene was used as the battery electrode binder for the positive electrode and polyvinyl alcohol was used as the binder for the battery electrode for the negative electrode.
Poor electrolyte resistance, severe capacity degradation, and poor battery characteristics.

[0028]

The binder for a battery electrode of the present invention can provide a battery electrode in a nickel-metal hydride battery, which maintains high conductivity, has excellent electrolyte resistance, and secures the binding property with a current collector. it can. In addition, since water is used as a dispersion medium, electrode fabrication is also facilitated. Further, the battery electrode of the present invention provides a nickel-metal hydride battery having excellent charge / discharge cycle characteristics.

Claims (2)

[Claims] (1) In the presence of 1 to 90 parts by weight of an organopolysiloxane, (a-1) 1 to 70% by weight of a (meth) acrylic acid alkyl ester unit having 1 to 3 carbon atoms in an alkyl group; 2) 25 to 97% by weight of (meth) acrylic acid alkyl ester units having 4 to 10 carbon atoms in the alkyl group, (b) ethylenically unsaturated carboxylic acid units and, if necessary, (c) copolymerizable therewith. Other monomer units [However, (a-1) + (a-2) + (b) + (c) =
100% by weight] of a monomer component 99 to 10 parts by weight [organopolysiloxane + monomer component = 100
Parts by weight] of a polyorganosiloxane-based polymer obtained by polymerizing the polymer. 2. A nickel-metal hydride battery electrode using the battery electrode binder according to claim 1.