KR19980071685A - Binder for Ni-MH Battery Electrode - Google Patents

Abstract

The present invention relates to a binder for nickel hydride battery electrodes, wherein the glass transition point is 5 ° C. or lower, the toluene insoluble content is 20 to 100% by weight, and is composed of an aqueous dispersion of a copolymer containing a functional group in the polymer.

The binder for the hydrogen storage electrode of the present invention has excellent electrolyte resistance and maintains high conductivity in a battery containing a hydrogen storage alloy and nickel hydroxide as an electrode active material, mainly a nickel-hydrogen secondary battery, and has high binding property with a current collector. It is possible to obtain a battery electrode having a. Moreover, since water is used as a dispersion medium, an electrode preparation stroke becomes easy. In addition, the hydrogen storage alloy electrode using the binder of the present invention provides a nickel hydrogen secondary battery excellent in charge and discharge cycle characteristics.

Description

Binder for Ni-MH Battery Electrode

The present invention relates to a binder for secondary battery electrodes excellent in binding property, charge and discharge cycleability, storage characteristics and safety. More specifically, the present invention relates to a binder composition for nickel hydrogen battery electrodes in which a hydrogen storage alloy in a nickel hydrogen battery is suitably used for a cathode held in a current collector and nickel hydroxide or the like held in a current collector.

In recent years, technological advances in the electronics industry have been remarkable, and demands for high energy density, safety, and the like have increased in battery technology. Nickel hydride batteries have a high energy density per unit volume and contain no pollutants, and thus attract attention as a battery having excellent safety.

Nickel-metal hydride batteries use a hydrogen storage alloy as an active material of a negative electrode, and the alloy freely releases hydrogen ions by generating heat and endotherm in a hydrogen atmosphere. Thus, the easy absorption and release of hydrogen ions leads to high capacity and long life.

In addition, nickel-metal hydride batteries have already been put to practical use in that they can be rapidly charged and discharged, have strong overcharge and overdischarge, and have high capacity, small size, and light weight.

In nickel-metal hydride batteries, a polymer binder is used to fix the active material to the current collector. The performance required for the binder is as follows. ① The binding property between the active material and the current collector should be good. It should move freely, ③ The volume should not change due to electrolyte or charge and discharge.

For example, fluorine-based polymers such as polytetrafluoroethylene and polyvinylidene fluoride have been known as binders for hydrogen absorbing alloys, but these fluorine-based polymers have poor binding properties with current collectors and are active during repeated charge and discharge cycles. There was a problem that peeling of the material is likely to occur. In order to solve this problem, for example, attempts have been made to use SEBS (styrene-ethylene-butyrene-styrene block copolymer), which is a thermoplastic elastomer. In addition, since an organic solvent such as toluene is used, there is a problem that the risk of ignition is great in the mixing process with the hydrogen storage alloy in the industrial scale production method.

An object of the present invention is a water-based system that does not have a risk of ignition during mixing of a hydrogen storage alloy and a binder in a nickel-metal hydride battery, maintains high conductivity with little influence on an electrode active material, and has excellent binding property with a current collector. It is to achieve long life and high capacity using.

The present invention provides a binder for a hydrogen storage electrode, characterized in that the glass transition point is 5 ℃ or less, toluene insoluble content 20 to 100% by weight, consisting of an aqueous dispersion of a copolymer containing a functional group in the polymer. do.

The present invention is described in detail below.

The copolymer used in the present invention has a toluene insoluble content of 20 to 100% by weight, preferably 30 to 90% by weight, particularly preferably 50 to 85% by weight.

In the present invention, the toluene insoluble content is formed by drying a film aqueous dispersion of 50% by weight of a solid content adjusted to pH 8 with 0.5 N ammonia water or 0.5 N hydrochloric acid at 120 ° C. for 1 hour, and then drying the film to 100 weight of the polymer weight. The mixture is poured into a container such as a Erlenmeyer flask with negative toluene, shaken for 3 hours, filtered through a 200 mesh filter, insoluble matters are collected, dried at 120 ° C for 1 hour, the weight of insolubles is measured, and the gel amount is obtained by the following equation. .

Gel amount = (toluene insoluble weight / weight before immersion) × 100 (%)

If the toluene insoluble content of the copolymer is less than 20% by weight, a polymer flow occurs when the electrode is formed and dried by heating to excessively cover the electrode active material and the overvoltage rises, making it impossible to use. Moreover, durability of potassium hydroxide which is electrolyte solution is also inferior, and the hydrogen storage alloy removed from the collector.

The glass transition point (Tg) of the copolymer used by this invention is 5 degrees C or less. When the Tg exceeds 5 ° C., the polymer film obtained by the copolymer lacks flexibility and tackiness, and the adhesion of the active material to the current collector is poor.

In the present invention, the copolymer is used as an aqueous dispersion. The average particle diameter of the copolymer particles dispersed in this aqueous dispersion is preferably 0.05 to 5 µm, more preferably 0.1 to 2 µm, and preferably smaller than 1/3 of the electrode active material.

The copolymer used in the present invention needs to have functional groups such as a carboxyl group, an acid anhydride group, glycidyl group, and an amino group, and it is preferable that such functional groups have a ratio of 0.1 to 10% in one molecule of the polymer, which is a pyrolysis gas. Obtained by chromatography.

If the functional group is less than 0.1%, the binder performance and chemical resistance of the copolymer are inferior, while if it is more than 10%, the water resistance and storage stability are poor, which is not preferable.

As a copolymer which can be used by this invention, Especially preferably, the following two types are mentioned.

(I) A copolymer consisting of an aromatic vinyl unit, a conjugated diene unit, a (meth) acrylic acid ester unit, and a functional group-containing compound unit (hereinafter also referred to as specific polymer I).

(II) in the presence of organopolysiloxane

(a) (meth) acrylic acid alkyl esters and

(b) ethylenically unsaturated carboxylic acids

Polyorganosiloxane type polymer obtained by superposing | polymerizing the monomer component containing these (Hereinafter, it is also called specific polymer II).

In addition, in this invention, a unit shows the structure derived from each monomer after a monomer has radically polymerized.

Specific Polymer I

As an aromatic vinyl unit which comprises the specific polymer I used by this invention, the structure after radical vinyl polymerization of aromatic vinyl compounds, such as styrene, (alpha) -methylstyrene, and divinylbenzene, is mentioned, Preferably styrene is used.

As a conjugated diene unit, the structure after the radical polymerization of conjugated diene compounds, such as 1, 3- butadiene and isoprene, is mentioned, Preferably butadiene is used.

Moreover, as a (meth) acrylic acid ester unit, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic acid i Butyl, n-amyl (meth) acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, 2-hexyl (meth) acrylate, octyl (meth) acrylate, i-nonyl (meth) acrylate, (meth) (Meth) acrylic-acid alkylesters, such as decyl acrylate; Although the structure after (meth) acrylic acid ester, such as hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, and ethylene glycol di (meth) acrylate, radically polymerizes, the structure is preferable (meth) One having less than 4 carbon atoms in the alkyl group of the (meth) acrylic acid alkyl ester such as butyl acrylate and methyl (meth) acrylate is used.

Moreover, as a functional group containing compound unit, Ethylenic unsaturated carboxylic acids, such as acrylic acid, (meth) acrylic acid, itaconic acid, fumaric acid, maleic acid; Alkylamides of ethylenically unsaturated carboxylic acids such as (meth) acrylamide and N-methylolacrylamide; Carboxylic acid vinyl esters, such as vinyl acetate and a vinyl propionate; Acid anhydrides, monoalkyl esters, monoamides of ethylenically unsaturated dicarboxylic acids; Aminoalkyl esters of ethylenically unsaturated carboxylic acids such as aminoethyl acrylate, dimethylaminoethyl acrylate and butylaminoethyl acrylate; Aminoalkylamides of ethylenically unsaturated carboxylic acids such as aminoethylacrylamide, dimethylaminomethyl methacrylamide and methylaminopropylmethacrylamide; Vinyl cyanide compounds such as (meth) acrylonitrile and α-croacrylonitrile; The structure after radical group polymerization of functional group containing compounds, such as unsaturated aliphatic glycidyl ester, such as glycidyl (meth) acrylate, The unsaturated carboxylic acid or ethylenically unsaturated carboxylic acid aminoalkylamide is preferable. Used.

In certain polymers I, usually, aromatic vinyl units are 20 to 55% by weight of the specific polymer, 30 to 60% by weight of the conjugated diene compound, 10 to 40% by weight of the (meth) acrylic acid ester and 0.1 to 10% by weight of the functional group-containing compound. , Preferably 2 to 10% by weight, more preferably 3 to 10% by weight.

Particular polymer I in the present invention can be prepared by emulsion polymerization of the monomers described above.

Specific Polymer II

The organopolysiloxane used for the polymerization of specific polymer II is obtained by condensing organosiloxane.

As an organosiloxane, what has a linear structure, a branched structure, and a cyclic structure can be used, It is preferable to have a cyclic structure, and especially the compound of following General formula (1) is preferable.

R ¹ m SiO (4-m) / 2

In formula, R <^1> is substituted or unsubstituted monovalent hydrocarbon, m shows the integer of 0-3.

In the above formula (1), examples of R ¹ include a methyl group, an ethyl group, a propyl group, a vinyl group, a phenyl group, and a substituted hydrocarbon group in which these are substituted with a halogen atom or a cyano group. Examples of the organosiloxane represented by the formula (1) include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trimethyltriphenylcyclotrisiloxane, and the like.

The organopolysiloxane may be a polyorganosiloxane having a weight average molecular weight of about 500 to 100,000 condensed (polycondensed), for example, in terms of polystyrene.

In the case where the organosiloxane is a polyorganosiloxane condensed in advance, the molecular chain terminal is blocked with, for example, a hydroxyl group, an alkoxyl group, a trimethylsilyl group, a dimethylvinylsilyl group, a methylphenylvinylsilyl group, a methyldiphenylsilyl group, or the like. You may be.

It is preferable that the organopolysiloxane used for the synthesis | combination of specific polymer II is co-condensed with the said organosiloxane by the graft crosslinking agent. By using the graft crosslinking agent, a polymer having a high graft rate is obtained, and thus a polymer having more excellent properties aimed at by the present invention is obtained.

The following four types of compounds can be mentioned as a graft crosslinking agent.

(i) A compound having an unsaturated group and alkoxysilyl group of the formula (2) together.

CH ₂ = C (R ² )-(CH ₂ ) _n -Ar

In formula, R <^2> is a hydrogen atom or a C1-C6 alkyl group, n shows the integer of 0-12.

Examples of R ^{2 in} Formula 2 include a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, further preferably a hydrogen atom or a methyl group. And n is an integer of 0 to 12, more preferably 0.

Specifically, p-vinylphenylmethyldimethoxysilane, 2- (m-vinylphenyl) ethylmethyldimethoxysilane, 1- (m-vinylphenyl) methyldimethylisopropoxysilane, 2- (p-vinylphenyl) ethyl Methyldimethoxysilane, 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- (tri Single compounds, such as ethoxysilyl) propyl] diphenylsilane, [3- (p-isopropenyl benzoylamino) propyl] phenyl propoxysilane, and mixtures thereof are mentioned. Among these, it is preferable to use p-vinylphenylmethyldimethoxysilane, 2- (p-vinylphenyl) ethylmethyldimethoxysilane, and 3- (p-vinylbenzoyloxy) propylmethyldimethoxysilane, and especially p-vinyl Preference is given to using phenylmethyldimethoxysilane.

(ii) a compound of formula 3;

R ³ p SiO (3-p) / 2

In formula, R <^3> is a vinyl group or an allyl group, P represents the integer of 0-2.

Specific examples include vinyl methyldimethoxysilane, tetravinyl tetramethylcyclotetrasiloxane, and allylmethyldimethoxysilane.

(iii) a compound of formula 4

HSR ⁴ SiR ⁵ _q O (3-q) / 2

In formula, R <^4> is a C1-C18 divalent or trivalent aliphatic saturated hydrocarbon group, R <^5> is a C1-C6 monovalent hydrocarbon group which does not contain an aliphatic unsaturated group, q represents an integer of 0-2. .

Specific examples thereof include 3-mercaptopropylmethyldimethoxysilane.

(iv) a compound of formula 5;

CH ₂ = C (CH ₃ ) -COO- (CH ₂ ) _r Sir ⁶ _s O (3-S) / 2

In formula, R <^6> is a hydrogen atom, a methyl group, an ethyl group, a propyl group, or a phenyl group, r is an integer of 0-6, s shows the integer of 0-2.

As a specific example, 3-methacryloxypropyl methyldimethoxysilane can be mentioned.

Particularly preferred among these graft crosslinkers are the compounds of formula (2).

The use ratio of the graft crosslinker is 20% by weight or less, preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, based on the total amount with the organosiloxane component. When the ratio of the graft crosslinking agent exceeds 20% by weight, the graft ratio increases, but when the proportion of the graft crosslinking agent increases, the polymer becomes low molecular weight, and as a result, sufficient binder performance cannot be obtained.

The polyorganosiloxane can be prepared by shear mixing and polycondensing the organosiloxane and graft crosslinker, if necessary, using a homo mixer or the like in the presence of an emulsifier (surfactant) and an aqueous medium.

Here, the emulsifier functions as an emulsifier of the organosiloxane and has a function as a condensation initiator.

Examples of the emulsifier include anionic surfactants such as unsaturated aliphatic sulfonic acid, hydroxyl aliphatic sulfonic acid, aliphatic substituted benzene sulfonic acid, and aliphatic hydrogen sulfates. , Dodecyl benzene sulfonic acid, cetyl benzene sulfonic acid, octyl sulfate, lauryl sulfate, orel sulfate, cetyl sulfate and the like.

In addition, in the specific polymer II, other anionic surfactant or nonionic surfactant may be used together with the anionic surfactant before emulsion polymerization or after emulsion polymerization within a range that does not impair the object of the present invention.

The amount of the emulsifier used in the present invention 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 graft crosslinking agent.

Moreover, the usage-amount of water is 100-500 weight part normally with respect to 100 parts of total amounts of an organosiloxane and a graft crosslinking component, Especially 200-400 weight part is preferable, and condensation temperature is 5-100 degreeC.

In the present invention, the polystyrene equivalent weight average molecular weight of the polyorganosiloxane is preferably 30,000 to 1,000,000, more preferably 50,000 to 300,000. If the weight average molecular weight of polystyrene conversion is less than 30,000, the intensity | strength of the coating film obtained will be inadequate, and if it exceeds 1,000,000, adhesiveness of a coating film will fall and it is unpreferable.

Particularly preferred among specific polymers II is (meth) acrylic acid alkyl ester having 1 to 3 carbon atoms of (a-1) alkyl group and (meth) acrylic acid having 4 to 10 carbon atoms of (a-2) alkyl group in the presence of organopolysiloxane. It is obtained by superposing | polymerizing the monomer component which consists of an alkyl ester, (b) ethylene unsaturated carboxylic acid, and (c) these and other monomers copolymerizable with these.

Here, as the (meth) acrylic acid alkyl ester having 1 to 3 carbon atoms of the (a-1) alkyl group, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, (meth) acrylic acid i-propyl, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, etc. are mentioned. The (meth) acrylic-acid alkylester whose carbon number of these (a-1) alkyl groups is 1-3 can be used individually by 1 type or in combination of 2 or more types.

As the (meth) acrylic acid alkyl ester having 4 to 10 carbon atoms of the (a-2) alkyl group, for example, (meth) acrylic acid n-butyl, (meth) acrylic acid i-butyl, (meth) acrylic acid n-amyl, (meth) I) amyl acrylate, hexyl (meth) acrylate, 2-hexyl (meth) acrylate, octyl (meth) acrylate, i-nonyl (meth) acrylate, decyl (meth) acrylate, and the like. The (meth) acrylic-acid alkylester of 4-10 carbon atoms of such an (a-2) alkyl group can be used individually by 1 type or in combination of 2 or more types.

The (meth) acrylic acid alkyl ester having 1 to 3 carbon atoms of the (a-1) alkyl group has an effect of increasing the expansion ratio to the electrolyte solution of the dried coating film of the obtained specific polymer II, thereby providing elasticity, strength and adhesion. The blending ratio is 1 to 70% by weight, preferably 3 to 55% by weight, more preferably 5 to 50% by weight based on the entire monomer component. When the blending ratio of the component (a-1) is less than 1% by weight, the dry coating film may be sticky, the strength may be lowered, and the binding property with the current collector and the electrolyte resistance may be inferior. On the other hand, when it exceeds 70 weight%, a dry coating film may become hard too much, and there exists a possibility that the active material may detach | desorb from a collector.

(a-2) The (meth) acrylic acid alkyl ester having 4 to 10 carbon atoms of the alkyl group has the effect of imparting elasticity, strength and adhesion to the specific polymer II obtained, and the blending ratio is 25 to 97 weight based on the entire monomer component. %, Preferably 30 to 95% by weight, more preferably 33 to 91% by weight. If the blending ratio of the component (a-2) is less than 25% by weight, the adhesiveness and strength of the dry coating film may be inferior.On the other hand, when the content of the component (a-2) is more than 97% by weight, the stability of the polymerization system may be inferior. Moreover, adhesiveness, strength, etc. may also fall.

Moreover, as (b) ethylenically unsaturated carboxylic acid, the compound etc. which were mentioned previously as a monomer component of specific polymer I are mentioned, Preferably it is (meth) acrylic acid. Such (b) ethylene unsaturated carboxylic acid has the effect of maintaining the balance of stability, water resistance, and electrolyte resistance of the specific polymer II obtained at high level, and can be used individually by 1 type or in combination of 2 or more types. The blending ratio of the component (b) is 0.5 to 15% by weight, preferably 2 to 13% by weight, more preferably 3 to 10% by weight based on the entire monomer component. If the blending ratio is less than 0.5% by weight, the binding property with the current collector may deteriorate, and the binder performance may be deteriorated. On the other hand, when the blending ratio is more than 15% by weight, the electrolyte resistance and the storage stability may be deteriorated.

(C) As another monomer copolymerizable with these, For example, Vinyl cyanide compounds, such as (meth) acrylonitrile and the (alpha)-acrylonitrile; Aliphatic conjugated dienes such as 1,3-butadiene, isoprene and 2-chrol-1,3-butadiene; Aromatic vinyl compounds such as styrene, α-methylstyrene, and vinyltoluene; Alkylamides of ethylenically unsaturated carboxylic acids such as (meth) acrylamide and n-methylolacrylamide; Carboxylic acid vinyl esters, such as vinyl acetate and a vinyl propionate; Acid anhydrides, monoalkyl esters, monoamides of ethylenically unsaturated dicarboxylic acids; Aminoalkyl esters of ethylenically unsaturated carboxylic acids such as aminoethyl acrylate, dimethylaminoethyl acrylate and butylaminoethyl acrylate; Aminoalkylamides of ethylenically unsaturated carboxylic acids such as aminoethylacrylamide, dimethylaminomethyl methacrylamide and methylaminopropylmethacrylamide; Unsaturated aliphatic glycidyl esters, such as glycidyl (meth) acrylate, etc. are mentioned, Acrylonitrile, (meth) acrylonitrile, 1, 3- butadiene, styrene, (alpha) -methylstyrene, etc. are preferable. These (c) copolymerizable other monomers can also be used individually by 1 type or in combination of 2 or more types.

The amount of the (c) copolymerizable other monomer is preferably 1 to 60% by weight in the monomer component, and when it exceeds 60% by weight, there may be problems such as deterioration in film formation, discoloration after film formation, and coating film shrinkage.

It is preferable to manufacture the specific polymer II by preparing the water dispersion of organopolysiloxane, and emulsion-polymerizing a monomer component in presence of an organopolysiloxane water dispersion.

When the monomer composition is polymerized in the presence of an aqueous dispersion of the organopolysiloxane, the insertion composition is 1 to 90 parts by weight, preferably 3 to 50 parts by weight, more preferably 5 to 30 parts by weight of the organopolysiloxane component (solid content). 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 (organopolysiloxane + monomer component = 100 parts by weight). If the organopolysiloxane is less than 1 part by weight, sufficient adhesion, electrolyte resistance, and water resistance may not be obtained. On the other hand, if it exceeds 90 parts by weight, sufficient strength as a coating film may not be obtained, and the film forming property may also deteriorate. .

Other copolymers

Other copolymers include styrene-isoprene copolymer, polyvinylidene prolide copolymer, and the like.

An aqueous dispersion of such a copolymer can also be synthesized by a conventional emulsion polymerization method.

The styrene-isoprene copolymer is prepared by emulsion polymerization of at least 30% by weight of isoprene, 30 to 60% by weight of styrene, and 0.1 to 10% by weight of the aforementioned functional group-containing compound.

The polyvinylidene prolide polymer is a polymer obtained by polymerizing a monomer comprising (a) 50 to 80 wt% of vinylidene fluoride, 20 to 50 wt% of propylene hexafluoride, and 0 to 30 wt% of other copolymerizable monomers, (b) fluoride 40 to 100% by weight of vinylidene and 20 to 50% by weight of propylene hexafluoropropylene and 0 to 30% by weight of other copolymerizable monomers and 40 to 100% by weight of (meth) acrylic acid ester and other copolymerizable monomers. The composite polymer etc. which the acrylic polymer which superposed | polymerized the monomer which consists of 0-60 weight% of monomers, etc. are mentioned.

The polyvinylideneprolide polymer is preferably synthesized in Japanese Patent Application Laid-Open No. 7-258499, and the polyorganosiloxane-based polymer is preferably synthesized by the method described in Japanese Patent Application Laid-Open No. 4-261454.

Binder for Battery Electrode

In the battery electrode binder of the present invention, as an additive, a thickener may be used in an amount of 1 to 200 parts by weight based on 100 parts by weight of the copolymer.

The water-soluble thickener includes carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, polyacrylic acid (salt), starch oxide, phosphorylated starch, casein and the like.

Moreover, solid content concentration of the water dispersion of a copolymer is 20-65 weight% normally, Preferably it is 35-60 weight%.

The binder for battery electrodes of this invention can be mix | blended with electrode materials, such as an electrode active material, and can be used as a composition for battery electrodes. At this time, if necessary, it may be molded together with the current collector, or may be applied to the current collector. The battery electrode is preferably obtained by applying a slurry-like composition for battery electrodes to a current collector, heating and drying.

As the coating method of the composition for battery electrodes, the slit coating method, the reverse roll method, the cornber method, the gravure method, the air knife method, etc. can be arbitrarily used. As the drying method, it is allowed to stand for drying, a blow dryer, a warm air dryer, an infrared heater, a far infrared heater, or the like. Can be used. It is preferable that drying temperature is 130 degreeC-200 degreeC normally.

The binder for battery electrodes of the present invention is blended in an amount of 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the electrode active material. If the compounding quantity of the battery electrode binder is less than 0.1 part by weight, good adhesive strength cannot be obtained. If it exceeds 20 parts by weight, the overvoltage is significantly increased, which adversely affects battery characteristics.

The composition for battery electrodes consists of an electrode active material and the binder for battery electrodes of the present invention, in addition to dispersants such as hexametaphosphate, soda tripolyphosphate, soda pyrophosphate, soda polyacrylic acid, and nonionics as stabilizers of latex, You may add additives, such as anionic surfactant.

When assembling a nickel-metal hydride battery using the composition for the battery electrode, nickel hydroxide is used as the active material of the positive electrode, and a hydrogen storage alloy powder is used as the negative electrode active material, and a part of Ni based on MmNi ₅ is Mn, Al, Co. Substituent with etc. is used suitably. Where Mm represents mismetal, which is a mixture of rare earths. The shape of the powder is a powder that has passed through 100 mesh, and the average particle size is about 3 to 400 µm because of problems such as a decrease in current efficiency, a decrease in slurry stability, and an increase in interparticle resistance in the coating film of the obtained electrode.

In addition, the active material for electrodes may be carbon fluoride, graphite, vapor-grown carbon fiber and / or its pulverized product, PAN-based carbon fiber and / or its pulverized product, pitch-based carbon fiber and / or ) Made of carbon materials such as pulverized products, conductive powders such as carbon powder, carbon nickel powder, cobalt powder, copper powder or conductive polymers such as polyacetylene, poly-p-phenylene, compounds such as tin oxide or fluorine An amorphous compound etc. are mix | blended with the active substance for electrodes. However, it does not specifically limit to these.

As a current collector to which the composition for electrodes is apply | coated, the core board of thickness 40-170 micrometers which consists of metals, such as nickel, for example is used. It is preferable that this core board is porous, and a nickel mesh, a punching nickel, a nickel plated punching metal, etc. are mentioned. At this time, the porosity of the metal core plate is usually 30 to 60%.

Nickel metal hydride battery

As an electrolytic solution of a nickel hydride battery, a mixed liquid in which any one or both of sodium hydroxide and lithium hydroxide is added to potassium hydroxide and potassium hydroxide of 5 or more specified is usually used.

Also preferably, components such as polarizers, current collectors, terminals, and insulating plates are used to constitute the battery. Moreover, although it does not specifically limit as a structure of a battery, It is a cylindrical battery or a square battery which wound the positive electrode, the negative electrode, More preferably, the paper type battery which made the polarizer single layer or multilayer, or the positive electrode, the negative electrode, More preferably, the polarizer rolled into roll shape. The form etc. can be mentioned as an example.

The battery electrode manufactured using the binder for battery electrodes of this invention can be used suitably specifically for AV equipment, OA equipment, communication equipment, and even an electric vehicle.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not at all limited by these examples. In addition, in this embodiment, unless otherwise specified, parts represent parts by weight.

Measure

(1) toluene gel amount measurement; The latex adjusted to pH 8 with 0.5 N aqueous ammonia and 0.5 N hydrochloric acid was dried at 120 ° C. for 1 hour to form a film, and then immersed in 100 parts by weight of toluene of polymer weight for 3 hours, followed by filtration through a 200 mesh filter. The powder was collected, dried at 120 ° C. for 1 hour, the weight of the insoluble was measured, and the gel amount was determined by the following formula.

Gel amount = (toluene insoluble weight / weight before immersion) × 100 (%)

(2) measuring the glass transition point; Using the filter shown in (1), the glass transition point was calculated | required using the Seiko Denshi Kogyo Co., Ltd. (differential scanning calorimeter).

(3) measuring the average particle diameter; The particle diameter was measured using the laser particle diameter analysis system LPA-3000s / 3100 made from Otsuka Denshi Corporation.

Synthesis Examples 1 to 5

70 parts of ion-exchanged water and 0.3 parts of potassium persulfate were respectively put into the autoclave provided with the stirrer, the gaseous-phase part was replaced by nitrogen gas for 15 minutes, and it heated up at 80 degreeC. On the other hand, the components shown in Table 1 and 0.2 weight part of emulsifier dodecylbenzenesulfonic acid were mixed in the separate container, and it was dripped at the said autoclave over 15 hours. During dripping, reaction was performed at 80 degreeC. After completion of the dropwise addition, the mixture was further stirred at 85 ° C for 5 hours, and then the reaction was completed. The pH was adjusted to 7 with potassium hydroxide cooled to 25 ° C., after which steam was introduced to remove residual monomer, and then concentrated to obtain an aqueous dispersion of polymers I to V.

Synthesis Example One 2 3 4 5 polymer I Ⅱ Ⅲ Ⅳ Ⅴ Compounding ratio (part by weight) BD 40 45 43 40 ST 40 36 44 37 30 IP 52 nBA 10 MMA 17 15 10 10 15 AA One One One One One IA 2 2 2 2 2 N-MAM One Toluene Gel Weight (%) 86 87 76 74 70 Tg (℃) -8 -18 -20 -21 -2 Average particle size (㎛) 0.1 0.2 0.2 0.2 0.2

In addition, the symbol of the monomer in Table 1 represents the following compounds.

BD = Butadiene

ST = styrene

IP = Isoprene

nBA = n-butylacrylate

MMA = methyl methacrylate

AA = acrylic acid

IA = Itaconic acid

N-MAM = N-methylolacrylamide

Synthesis Example 6

(1) 1.5 parts of vinylphenylmethyldimethoxysilane and 98.5 parts of octamethylcyclotetrasiloxane were mixed, and this was mixed with α-olefinsulfonic acid (RCH = CH (CH ₂ ) _n SO ₃ Na about 75% by weight, RCH ₂ CH (OH) (CH ₂ ) _m SO ₃ Na (a mixture of about 25% by weight) 2.0 parts was added to 300 parts of dissolved distilled water, followed by stirring for 3 minutes with a homomixer to emulsify and disperse. The mixture was transferred to a detachable flask equipped with a condenser, a nitrogen inlet, and a stirrer, and heated at 90 ° C. for 6 hours while stirring and mixing. Condensation was completed by cooling at 5 ° C for 24 hours. The obtained organic polysiloxane aqueous dispersion was neutralized to pH 7 with aqueous sodium carbonate solution.

(2) In a detachable flask equipped with a condenser, a nitrogen inlet and a stirrer, 100 parts by weight (solid content) of the organic polysiloxane aqueous dispersion (solid) obtained in (1), 70 parts of ion-exchanged water, and 0.3 part of ammonium persulfate were added, respectively. Substituted with nitrogen gas for a minute, it heated up at 80 degreeC.

(3) On the other hand, in a separate container, the monomer component consisting of 71 parts of n-butyl acrylate, 8 parts of glycidyl methacrylate and 21 parts of styrene was mixed and added dropwise to the organic polysiloxane aqueous dispersion of (2) over 3 hours. During dripping, reaction was performed at 80 degreeC, introducing nitrogen gas. After completion of the dropwise addition, the mixture was stirred at 85 ° C for 2 hours, and then the reaction was terminated. Then, it cooled to 25 degreeC and adjusted to pH 7 with ammonia water, and obtained the water dispersion of the specific polymer (polymer VI).

Synthesis Examples 7 to 11

In the process (2) and (3) of the synthesis example 6, except having used the composition shown in Table 2, it carried out similarly to the synthesis example 6, and obtained the water dispersion of the polymer (VIII).

Synthesis Example 6 7 8 9 10 11 polymer Ⅵ Ⅶ Ⅷ Ⅸ Ⅹ ? Organopolysiloxane (parts by weight (solid content)) 100 100 100 100 50 200 Monomer (parts by weight) MMA 5 11 11 11 EMA 26 n-BA 71 90 70 76 85 85 MAA 3 2 One 2 2 N-MAM 2 2 One 2 2 MAN 11 GMA 8 ST 21 Toluene Gel Weight (%) 99 99 98 100 100 99 Tg (℃) -105 -110 -109 -109 -50 -115 Average particle size (㎛) 0.4 0.3 0.3 0.3 0.3 0.3

In addition, the symbol of the monomer in Table 2 shows the following compounds.

MMA = methyl methacrylate (component (a-1))

EMA = ethyl methacrylate (component (a-1))

nBA = n-butylacrylate (component (a-2))

MAA = methacrylic acid ((b) component)

N-MAN = N-methylol acrylamide ((c) component)

MAN = methacrylonitrile ((c) component)

GMA = glycidyl methacrylate ((c) component)

ST = styrene ((c) component)

Synthesis Example 12

(1) Contents equipped with an electronic stirrer After sufficiently replacing the autoclave of about 6 liters with nitrogen gas, 2.5 liters of pure deoxygenated water and 25 g of ammonium perfluorodecanoate as an emulsifier were added and stirred at 350 rpm. It heated up to 60 degreeC. Subsequently, a mixed gas composed of 44.2% by weight of vinylidene fluoride and 55.8% by weight of propylene hexafluoride was added until it became 20 kg / cm ² G, containing 20% by weight of diisopropylperoxydicarbonate as a polymerization initiator. Polymerization was initiated by injecting 25 g of a solution of Pron 113 with nitrogen gas. Since the pressure dropped as the polymerization proceeded, the mixture gas composed of 60.2% by weight of vinylidene fluoride and 39.8% by weight of propylene hexafluoride was sequentially press-fitted to maintain the pressure at 20 kg / cm ² G to continue the reaction. Since the polymerization rate was lowered with the reaction time, after 3 hours, the same amount of the polymerization initiator was again indented with nitrogen gas, and the reaction was continued for another 3 hours. Subsequently, after cooling the inside of the system and stopping stirring, the unreacted monomer was released to stop the reaction to obtain a water-containing body of the fluorine-containing polymer.

(2) Substituting the inside of a 7-liter detachable flask with nitrogen, 150 parts of the resulting fluorinated polymer aqueous dispersion in terms of solids and 2- (1-allyl) -4-nonylphenoxypolyethylene glycol sulfate ammonium 3 Part was added and the temperature was raised to 75 ° C. Subsequently, 29 parts of styrene, 68 parts of n-butylacrylate, 2 parts of acrylic acid, and 1 part of N-methylol acrylamide were added, and it stirred at 75 degreeC for 30 minutes. 0.5 part of sodium persulfate was added thereto, polymerized at 85 to 95 ° C for 2 hours, cooled, and the reaction was stopped to obtain an aqueous dispersion of a polyvinylideneprolide polymer (hereinafter referred to as polymer?).

Comparative Synthesis Examples 1-3

In the synthesis example 1, the water dispersions of the polymers (v) to (v) were obtained in the same manner as in the synthesis example 1 except that the composition of the monomer components was as shown in Table 3.

Comparative Synthesis Example One 2 3 polymer Ⅰ Ii Ⅲ ST 62 58 45 IP 20 40 nBA 15 32 15 AA One IA 2 GMA 10 Toluene Gel Weight (%) 82 96 0 Tg (℃) 24 27 -6 Average particle size (㎛) 0.2 0.3 0.2

In addition, the symbol of the monomer in Table 3 shows the following compounds.

ST = styrene

IP = Isoprene

nBA = n-butylacrylate

MMA = methyl methacrylate

AA = acrylic acid

IA = Itaconic acid

GMA = glycidyl methacrylate

Example 1

Water dispersion 1 of the polymer I prepared in Synthesis Example 1 with 100 parts of hydrogen absorbing alloy powder having an average particle diameter of 170 μm (La 0.99% by weight, 3.41% by weight of Ni, 1.20% by weight of Co, 0.10% by weight of Mn, and 0.29% by weight of Al). In addition, 1 part of polyvinyl alcohol aqueous solution was added as solid content as a thickener, it mixed well, the composition for battery electrodes was produced, and the following experiment was performed using the obtained battery electrode. The results are shown in Tables 4 and 5.

(1) binding with Ni mesh; The obtained composition for battery electrodes was coated with a thickness of 400 g / m 2 using an Ni mesh having a thickness of 1 mm as an applicator, and dried and pressed at 150 ° C. for 20 minutes to obtain a battery electrode having a thickness of 200 μm.

After sticking and peeling an adhesive tape to the obtained battery electrode, it evaluated the grade of the coating film adhering to an adhesive surface. For example, five points of the time when a coating film is hardly adhered to an adhesive surface, and the case where the coating film of the whole adhesive surface peeled are made into one point.

(2) Measurement method of conductivity: The battery electrode composition was coated to a thickness of 400 g / m 2 on a 100 μm PET film, dried at 150 ° C. for 20 minutes, and pressed to obtain a coating film having a thickness of 200 μm. Its resistance was measured by the four-terminal method.

(3) electrolyte resistance; The battery electrode obtained in said (1) was immersed in electrolyte solution (6N KOH aqueous solution) for 24 hours. The case where there is no change is made into 5 points and the case where it peeled completely is made into 1 point.

(4) battery characteristics; Nickel oxide on the positive electrode and the battery electrode obtained in (1) above were used as the negative electrode, cut into 0.9 cm x 5.5 cm, and welded to Ni lead wires, respectively. It was.

The battery was charged to 2.0 V, and the cycle of discharging from 10 mA to 1.0 V was repeated to measure the capacity retention rate. Moreover, the cell charged with 2.0V was preserve | saved at 70 degreeC for 30 days, and storage stability was measured.

Examples 2 to 7, Comparative Examples 1 to 3

Except having used the polymer shown in Table 4 instead of the polymer 1 in Example 1, it carried out similarly to Example 1, and produced and evaluated the composition for battery electrodes and a battery. The results are shown in Tables 4 and 5 together.

polymer Binding Conductivity (mΩ / cm) Electrolytic solution resistance Example One I 4 30 5 2 Ⅱ 4 35 4 3 Ⅲ 5 25 5 4 Ⅳ 5 28 4 5 Ⅴ 4 35 4 6 Ⅵ 5 28 5 7 Ⅶ 5 25 5 Comparative example One Ⅰ One 35 One 2 Ii 2 37 3 3 Ⅲ One 42 2

Capacity maintenance rate (%) (the first cycle) % Decrease in capacity after 100% filling and storage at 70 ° C for 30 days 10 cycles 100 cycles 300 cycles Example One 99.9 97.8 97.0 3.1 2 99.9 97.9 96.8 3.2 3 99.9 98.0 98.1 2.5 4 99.9 98.0 96.6 3.0 5 99.9 98.1 97.8 2.5 6 99.9 98.0 97.6 2.4 7 99.9 98.1 97.5 2.5 Comparative example One 99.0 92.3 75.3 28.4 2 99.4 95.8 82.2 15.3 3 99.4 88.8 71.2 19.3

Example 8

(1) Preparation of composition (for positive electrode) for battery electrodes

A mixed powder consisting of 100 parts by weight of nickel hydroxide, 3 parts by weight of nickel powder and 1 part by weight of cobalt powder, 1 part by weight of the polymer (VIII) obtained in Synthesis Example 7 as solids and 1 part by weight of an aqueous solution of carboxymethylcellulose as a thickener as a solid Composition A for electrodes was prepared.

(2) Preparation of composition (for negative electrode) for battery electrodes

100 parts by weight of a 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, Mn: 0.1% by weight, Al: 0.29% by weight), and a specific surface area of 100 cm 2 / g 10 parts by weight of Kechant Black, 1 part by weight of polymer VII obtained in Synthesis Example 7 and 1 part by weight of carboxymethylcellulose as a solid as a thickener were prepared to prepare a composition for a battery electrode.

(3) Fabrication and evaluation of anode sheet

The composition A for battery electrodes obtained by (1) was coated with the thickness of 400 g / m <2> on the collector which consists of foamed nickel, and it dried for 20 minutes at 150 degreeC, and obtained the positive electrode sheet of 200 micrometers of TLZU thicknesses. After the adhesive tape was attached to the obtained positive electrode sheet and then peeled off, the state of the coating film adhered to the adhesive face of the tape was observed. Since the coating film was hardly adhered to the adhesive face, the obtained positive electrode sheet was excellent in binding property.

(4) Fabrication and evaluation of negative electrode sheet

Using a punching metal having a thickness of 60 µm plated with Ni having a porosity of 50% as a current collector, the composition B for a battery electrode obtained in (2) was coated with a thickness of 400 g / m 2, dried at 150 ° C. for 20 minutes, and pressed to obtain a thickness of 200. A micrometer negative electrode sheet was obtained. After sticking and peeling off the adhesive tape on the obtained negative electrode sheet, the state of the coating film adhered to the adhesive surface of the tape was observed, and binding property was evaluated by the following 5-point method. The results are shown in Table 6.

5 points | pieces: When the coating film is hardly attached to the adhesive surface

4 points | pieces: When the coating film is affixed more than 70% and less than 90% of the adhesive surface surface area.

3 points | pieces: When the coating film is affixed more than 40% and less than 70% of the adhesive surface surface area.

2 points | pieces: When the coating film is affixed more than 10% and less than 40% of the adhesive surface surface area.

1 point: When the coating film is affixed on the whole adhesive surface.

(5) evaluation of conductivity

The composition B for battery electrodes was coated on the film of 100 micrometers in thickness of 400 g / m <2>, and it dried at 150 degreeC for 10 minutes, and obtained the coating film of 120 micrometers in thickness. Using this, the electrical resistance was measured by the 4-terminal method. The results are shown in Table 6.

(6) electrolyte resistance

The negative electrode sheet obtained in the above (4) was immersed in an electrolyte solution composed of 6 N potassium hydroxide aqueous solution at room temperature for 24 hours, and peeling of the coating film from the current collector was observed to evaluate the electrolyte resistance by the following five-point method. The results are shown in Table 6.

5 points: little change

4 points | pieces: When the coating film peels to 70% or more and less than 90% of the surface area of an electrical power collector.

3 points | pieces: When the coating film peels from 40% or more and less than 70% of the surface area of an electrical power collector.

2 points | pieces: When the coating film peels from 10% or more and less than 40% of the surface area of an electrical power collector.

1 point: When a coating film peels completely.

(7) Construction and evaluation of nickel hydride battery

The positive electrode sheet and the negative electrode sheet were cut into 0.9 x 5.5 cm, and Ni wires were welded to each of them, and a nickel hydrogen battery was assembled using a polypropylene nonwoven fabric as a polarizer using 6 N potassium hydroxide aqueous solution as an electrolyte.

The battery was charged to 2.0 V and discharged from 100 mA to 1.0 V was repeated to measure capacity retention. Moreover, the cell charged with 2.0V was preserve | saved at 70 degreeC for 30 days, and the capacity | capacitance fall rate was measured. The results are shown in Table 7.

Examples 9-12, Comparative Examples 4-7

Except having made the polymer used for a positive electrode and a negative electrode into the composition shown in Table 6, it carried out similarly to Example 8, and measured the binding property, electroconductivity, electrolyte resistance, capacity | capacitance retention rate, and capacity | capacitance reduction rate of a negative electrode. The results are shown in Tables 6 and 7.

Anode polymer Cathode polymer Binding (point) Conductivity (mΩ / cm) Electrolytic solution resistance (point) Kinds part Kinds part Example 8 Ⅶ One Ⅶ One 4 20 4 Example 9 a One Ⅷ One 5 30 4 Example 10 a 3 Ⅸ One 4 19 5 Example 11 a 3 Ⅹ One 5 25 4 Example 12 a 3 ? One 5 33 5 Comparative Example 4 a 3 Ⅰ One One 44 2 Comparative Example 5 a 3 Ii One 2 55 One Comparative Example 6 a 3 Ⅲ One 3 40 2 The number of polymers is the weight part in solid content. Symbols a and b of the polymers represent the following polymers: a: polytetrafluoroethylene b: polyvinylidene fluoride

Capacity maintenance rate (%) (the first cycle) Capacity degradation rate (%) 10 cycles 100 cycles 500 cycles Example 8 99.9 99.7 99.0 1.0 9 99.9 99.8 98.9 0.8 10 99.9 99.5 98.6 1.6 11 99.9 99.3 98.2 1.3 12 99.9 99.7 98.5 1.5 Comparative example 4 96.0 82.7 77.4 22.0 5 88.1 78.6 61.9 38.0 6 99.0 92.9 88.2 13.9

The binder for the hydrogen storage electrode of the present invention has excellent electrolyte resistance and maintains high conductivity in a battery containing a hydrogen storage alloy and nickel hydroxide as an electrode active material, mainly a nickel-hydrogen secondary battery, and has high binding properties with current collectors. A battery electrode can be obtained. Moreover, since water is used as a dispersion medium, an electrode preparation stroke becomes easy. In addition, the hydrogen storage alloy electrode using the binder of the present invention provides a nickel hydrogen secondary battery excellent in charge and discharge cycle characteristics.

Claims (6)

The binder for nickel-metal hydride battery electrodes whose glass transition point is 5 degrees C or less, a toluene insoluble content is 20 to 100 weight%, and consists of the aqueous dispersion of the copolymer containing a functional group in a polymer. The binder for nickel hydride battery electrodes according to claim 1, wherein the binder comprises an aqueous vinyl dispersion, a conjugated diene unit, a (meth) acrylic acid ester unit, and a functional group-containing compound unit. The method according to claim 2, wherein the composition comprises an aromatic vinyl unit, a conjugated diene unit, a (meth) acrylic acid ester unit, and a functional group-containing compound unit, wherein the (meth) acrylic acid ester unit is 10 to 40% by weight of the copolymer. A binder for nickel hydride battery electrodes, comprising an aqueous dispersion of coalescence. The method according to claim 2, characterized in that it comprises 20 to 55% by weight of aromatic vinyl units, 30 to 60% by weight of conjugated diene units, 10 to 40% by weight of (meth) acrylic acid ester units and 0.1 to 10% by weight of functional group-containing compounds. A binder for nickel hydride battery electrodes, comprising a water dispersion of a copolymer. The method of claim 1 wherein in the presence of an organopolysiloxane (a) (meth) acrylic acid alkyl esters and (b) ethylenically unsaturated carboxylic acids A binder for nickel metal hydride battery electrodes, comprising a polyorganosiloxane polymer obtained by polymerizing a monomer component containing a polymer as a main component. The method of claim 5, wherein in the presence of 1 to 90 parts by weight of the organopolysiloxane (a-1) 1 to 70% by weight of (meth) acrylic acid alkyl ester having 1 to 3 carbon atoms of the alkyl group, (a-2) 25 to 97% by weight of (meth) acrylic acid alkyl ester having 4 to 10 carbon atoms of the alkyl group, (b) ethylenically unsaturated carboxylic acids and (c) other monomers copolymerizable with these (Wherein (a-1) + (a-2) + (b) + (c) = 100% by weight) of 99 to 10 parts by weight of the monomer component (however, organopolysiloxane + monomer component = 100 parts by weight) A binder for nickel hydride battery electrodes, comprising a polyorganosiloxane polymer obtained by polymerizing a polymer as a main component.