JPH0613080A - Binder for hydrogen storage alloy electrode and electrode composite containing it - Google Patents

Abstract

PURPOSE:To provide a binder for hydrogen storage alloy electrode capable of forming a battery excellent in discharge capacity, charge/discharge cycle characteristic, and electrode durability, and an electrode composite containing this binder. CONSTITUTION:A binder for hydrogen storage alloy electrode contains a vinyl aromatic compound polymer block and a conjugate diene polymer block. In a block copolymer in which the weight ratio of vinyl aromatic compound to conjugate diene is 5-60:95-40, the total bond content of vinyl aromatic compound is 3-50wt.% of all monomers, and the vinyl bond content of conjugate diene part exceeds 50mol%, at least 30% of double bond in the conjugate diene part contains a hydrogen-added conjugate diene block copolymer to which hydrogen is added. Such a binder for hydrogen storage alloy electrode forms a hydrogen storage alloy electrode composite together with a hydrogen storage alloy and a conductive material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen storage alloy electrode binder containing a hydrogenated conjugated diene block copolymer and an electrode composition containing the same.

[0002]

2. Description of the Related Art In recent years, the progress of electronic industry technology has been remarkable, and the demand for high energy density, safety and the like has been increasing even in battery technology. Among them, the nickel / hydride battery has particularly attracted attention as a battery having a high energy density per unit volume and containing no pollutant and thus being excellent in safety. Hydrogen storage alloys used as negative electrode active materials for such batteries include rare-earth alloys based on LaNi ₅ , MmNi ₅ (Mm: misch metal), TiNi, Ti ₂ Ni, Ti _1-x Zr _x Ni. Titanium-based materials such as ZrV _0.4 Ni _1.6 and Laves phase materials such as ZrV _0.4 Ni _1.6 are known. As a method of molding these hydrogen storage alloys into electrodes, for example, alloy powder pulverized to several tens of microns and a conductive material (for example, nickel, copper, carbon, etc.) as a binder (for example, polytetrafluoroethylene, fluorinated ethylene) Propylene polymer, polyethylene, nylon, etc.) and press-bonding the mixture to a porous nickel plate, which is a current collector, or the mixture is pasted with a water-soluble binder such as polyvinyl alcohol In addition to the method of filling and pressing in the above, there is a method of mixing particles of the hydrogen storage alloy described above with a conductive material coated by plating, mixing with a binder, and crimping or filling the mixture with a current collector. Are known. However, in these methods, the binder is generally insoluble or sparingly soluble in the solvent, and is mixed with the alloy particles or the conductive material in a solid state, so that it is highly filled, uniformly dispersed, and with a current collector. Problems such as adhesion occurred, and as a result, the discharge capacity of the electrode and the charge / discharge cycle characteristics were unsatisfactory. When a water-soluble binder such as polyvinyl alcohol is used, when the battery is constructed,
There is a problem that the water-soluble binder is dissolved in the electrolytic solution and the discharge characteristics of the battery are deteriorated. Also, Japanese Patent Laid-Open No. 1-2531
In JP-A-59-59, it is proposed to use a thermoplastic elastomer composed of a styrene-ethylene-butadiene-styrene block copolymer as a binder. However, even when this binder is used, charging / discharging does not occur. Cycle characteristics related to discharge capacity, electrode durability, etc. when repeated many times were not sufficient. On the other hand, the applicants
Already, by using a solvent-soluble binder such as styrene-ethylene-butylene-styrene block copolymer, styrene-ethylene-propylene block copolymer, hydrogenated nitrile-butadiene copolymer, hydrogenated polybutadiene, Although it has been clarified that the cycle characteristics are considerably improved (see Japanese Patent Application Laid-Open No. 4-22067), a better solvent-soluble binder including the cycle characteristics has been desired.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a hydrogen storage alloy electrode which is soluble in an ordinary solvent and which can provide a battery having remarkably improved cycle characteristics when charging and discharging are repeated. A binder for use, and an electrode composition containing the binder.

[0003]

According to the present invention According to an aspect of the problem is, A ₁ -B ₁ consisting of (1) a vinyl aromatic compound polymer block A ₁ and the conjugated diene polymer block B ₁
A ₁ -B _1- containing a block copolymer, a gradient block C ₁ composed of a vinyl aromatic compound and a conjugated diene, in which the content of the vinyl aromatic compound is gradually increased or decreased.
A block copolymer selected from the group consisting of a C ₁ block copolymer and an A ₁ -B ₁ -a ₁ block copolymer further containing a vinyl aromatic compound polymer block a _1.
(i) wherein the weight ratio of vinyl aromatic compound to conjugated diene is 5 to 6
0: 95-40, the total bond content of vinyl aromatic compounds in blocks A ₁ , C ₁ and a ₁ is 3 to 50% by weight of all monomers and the total bond content of vinyl aromatic compounds in block A ₁ is total. In the block copolymer (i) in which at least 3% by weight of the monomer and the vinyl bond content of the conjugated diene moiety in the block B ₁ exceeds 50 mol%, at least 30% of the double bond of the conjugated diene moiety is hydrogenated. Binder for hydrogen storage alloy electrode (hereinafter referred to as "binder (I)"), which contains the hydrogenated conjugated diene-based block copolymer as described above, or (2) vinyl aromatic compound vinyl consists of a polymer block a ₂ and a vinyl aromatic compound random copolymer consisting of the block B ₂ a ₂ -B ₂ block copolymers of a conjugated diene, a vinyl aromatic compound and a conjugated diene A ₂ -B ₂ -C ₂ block copolymer content contains further inclined block C ₂ to increased or decreased gradually in aromatic compounds, and A ₂ -B further contains a vinyl aromatic compound polymer block a ₂
A ₂ -a ₂ block copolymer than consisting block copolymer selected from the group (ii), the weight ratio of the vinyl aromatic compound and a conjugated diene is 5-6
0: 95 to 40, bond content of the block A _2, C ₂ and a total bond content vinyl aromatic compound and in the block A ₂ by 3 to 25% by weight of the total monomers of a vinyl aromatic compound in ₂ total In the block copolymer (ii) in which at least 3% by weight of the monomer and the vinyl bond content of the conjugated diene moiety in the block B ₂ is 15 mol% or more, at least 30% of the double bond of the conjugated diene moiety is hydrogenated. It is achieved by a binder for hydrogen storage alloy electrodes (hereinafter, referred to as "binder (II)") containing the hydrogenated conjugated diene-based block copolymer.

The present invention will be described in detail below. Binder for hydrogen storage alloy electrode First, the vinyl aromatic compound that is a constituent monomer of the block copolymer (i) in the binder (I) or the block copolymer (ii) in the binder (II) is A compound having one or more vinyl groups bonded to an aromatic group having a carbon ring or a heterocycle, or a derivative thereof. Specific examples of the vinyl aromatic compound include styrene, t-butylstyrene, α
-Methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-
Examples thereof include aminoethyl styrene and vinyl pyridine, and styrene and α-methyl styrene are particularly preferable. These vinyl aromatic compounds are used alone or in combination of two or more.

Further, the conjugated diene which is a constituent monomer of the block copolymer (i) or the block copolymer (ii) is a linear or branched compound having an aliphatic conjugated double bond, It is a compound copolymerizable with a vinyl aromatic compound. Specific examples thereof include 1,3-butadiene,
Isoprene, 2,3-dimethyl-1,3-butadiene,
1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,
3-octadiene, 3-butyl-1,3-octadiene, chloroprene and the like can be mentioned, but from the viewpoints of industrial ease of use, properties as a binder and the like, 1,3
-Butadiene, isoprene and 1,3-pentadiene are preferred, and 1,3-butadiene is particularly preferred. These conjugated dienes may be used alone or in admixture of two or more.

Block copolymer (i) in binder (I)
Is an A ₁ -B ₁ block copolymer consisting of a vinyl aromatic compound polymer block A ₁ and a conjugated diene polymer block B ₁ , a vinyl aromatic compound and a conjugated diene, and the content of the vinyl aromatic compound is gradually increased. Alternatively, an A ₁ -B ₁ -C ₁ block copolymer further containing a gradually decreasing gradient block C ₁ and an A ₁ -B ₁ -a ₁ block copolymer further containing a vinyl aromatic compound polymer block a ₁ Is selected from the group consisting of: These block copolymers (i) are used alone or in admixture of two or more.

The block copolymer (ii) in the binder (II) is composed of a vinyl aromatic compound polymer block A ₂ and a random copolymer block B _{2 of a} vinyl aromatic compound and a conjugated diene. ₂ -B ₂ block copolymer,
A ₂ -B ₂ -C ₂ block copolymer further contains a gradient block C ₂ the content of the vinyl aromatic compound consists of a vinyl aromatic compound and a conjugated diene is increased or decreased gradually, and vinyl aromatic compound polymer are those selected from the group consisting of a ₂ -B ₂ -a ₂ block copolymer further contains blocks a _2. These block copolymers (ii) are used alone or in admixture of two or more.

The weight ratio of the vinyl aromatic compound to the conjugated diene in the block copolymer (i) and the block copolymer (ii) is 5 to 60:95 to 40, preferably 7 to 4
It is 0: 93-60. However, the total amount of the vinyl aromatic compound and the conjugated diene is 100. When the weight ratio of these vinyl aromatic compounds is less than 5, when the hydrogenated conjugated diene-based block copolymer is used as a binder for a hydrogen storage alloy electrode, the mechanical strength of the electrode is insufficient and the hydrogen storage alloy It becomes easy to fall off, and when it exceeds 60,
The binder is too hard, and the stress acting during charging / discharging easily causes cracks in the electrode, which may lead to deterioration in electrode performance.

In the binder (I), blocks A ₁ and C ₁
And the total bond content of vinyl aromatic compounds in a ₁ is
3 to 50 of all monomers constituting the block copolymer (i)
The content of vinyl aromatic compounds in the block A ₁ must be at least 3% by weight of the total monomers constituting the block copolymer (i). When the total bond content of the vinyl aromatic compounds in the blocks A ₁ , C ₁ and a ₁ is less than 3% by weight, when the hydrogenated conjugated diene-based block copolymer is used as the binder, the hydrogen storage alloy and the conductive material are not used. Since the mixed state of is likely to be non-uniform, the discharge capacity of the battery may decrease. On the other hand, if it exceeds 50% by weight, the binder will be too hard and the electrode will crack due to the stress acting during charging and discharging. It will be easier. Also, when the bond content of the vinyl aromatic compound in the block A ₁ is less than 3% by weight, the mixed state with the hydrogen storage alloy and the conductive material is likely to be non-uniform, which may reduce the discharge capacity of the battery. . The total bond content of vinyl aromatic compounds in blocks A ₁ , C ₁ and a ₁ is 5-4.
0% by weight is preferable, and more preferably 5 to 25% by weight.
And the bond content of the vinyl aromatic compound in the block A ₁ is preferably 3 to 20% by weight.

In the binder (II), the total bond content of vinyl aromatic compounds in the blocks A ₂ , C ₂ and a ₂ is 3 to 25 of all the monomers constituting the block copolymer (ii). Must be% by weight and block A ₂
The vinyl aromatic compound bond content therein should be at least 3% by weight of the total monomers constituting the block copolymer (ii). When the bond content of the vinyl aromatic compound in the blocks A ₂ , C ₂ and a ₂ is less than 3% by weight, when the hydrogenated conjugated diene block copolymer is used as a binder, it does not react with the hydrogen storage alloy and the conductive material. Since the mixed state tends to be non-uniform, the discharge capacity of the battery may decrease. On the other hand, if it exceeds 25% by weight, the binder is too hard,
Due to the stress acting during charge / discharge, the electrode is likely to crack. Also, when the bond content of the vinyl aromatic compound in the block A ₂ is less than 3% by weight, the mixed state with the hydrogen storage alloy and the conductive material is likely to be non-uniform, which may reduce the discharge capacity of the battery. . The bond content of the vinyl aromatic compound in the blocks A ₂ , C ₂ and a ₂ is 5 to 20.
The content of vinyl aromatic compound in the block A ₂ is preferably 5 to 15% by weight, more preferably 8 to 18% by weight.

In the binder (I), the vinyl bond content of the conjugated diene moiety in block B ₁ must exceed 50 mol%. The vinyl bond here means 1,2 when the conjugated diene has a 1,3-conjugated double bond.
-Or means a monomer unit polymerized with a double bond at the 3,4-bonding position. When the vinyl bond content is 50 mol% or less, mechanical breakdown of the electrode is likely to occur when the hydrogenated conjugated diene block copolymer is used as a binder. The vinyl bond content of the conjugated diene moiety in the block B ₁ is preferably 70 mol% or more, more preferably 8 mol% or more.
It is 0 mol% or more.

In the binder (II), the block B ₂
The vinyl bond content of the conjugated diene moiety therein should be at least 15 mol%. The vinyl bond as used herein means the same monomer unit as in the case of the binder (I). When the vinyl bond content is less than 15 mol%, when the hydrogenated conjugated diene block copolymer is used as a binder,
Mechanical breakdown of the electrode is likely to occur. The vinyl bond content of the conjugated diene moiety in block B ₂ is preferably 30.
˜95 mol%, more preferably 40 to 90 mol%.

Further, the block copolymer (i) in the binder (I) and the block copolymer (i in the binder (II)
At least 30% of the double bonds of the conjugated diene moiety in i) must be hydrogenated. When the hydrogenation rate is less than 30%, the discharge capacity of the obtained battery, the cycle characteristics when charging and discharging are repeated, and the like are deteriorated. this is,
It is considered that after the battery is constructed, hydrogen generated by the charge / discharge reaction causes nonuniform hydrogenation of the double bond remaining in the conjugated diene portion, which hinders the battery performance. The hydrogenation rate of the double bond of the conjugated diene moiety in the block copolymer (i) and the block copolymer (ii) is preferably 50% or more, more preferably 90%.
~ 100%.

The block copolymer (i) or (ii) used in the binder (I) or (II) of the present invention can be produced by a known method. Polymerization therefor is usually carried out in a suitable solvent, for example, organic lithium compound-polar compound system, vanadium compound, molybdenum compound, chromium compound, zirconium compound, metal compound such as titanium compound-organoaluminum system, palladium compound system, ruthenium. It can be performed by so-called living polymerization using a polymerization initiator such as a compound-organophosphine-based polymerization initiator. In these polymerizations, a monomer that forms each block is usually added stepwise in order to impart a required block structure. Block copolymer A ₁ -B ₁ -C ₁
Alternatively, in A ₂ -B ₂ -C ₂ , the graded block C ₁ or C _{2 in} which the content of the vinyl aromatic compound is gradually increased or decreased, the monomer composition is continuously or continuously changed during the polymerization for forming the block C ₁ or C _2. It can be obtained by changing in stages. In this case, the content of the vinyl aromatic compound, along the molecular chain of the block C ₁ or C _2, may be increased as the distance from the block B ₁ or B _2, or may be decreased.

The hydrogenation of the block copolymer (i) or (ii) can also be carried out by a known method.
In this hydrogenation reaction, usually, the block copolymer (i) or (ii) is dissolved in a suitable solvent and treated with hydrogen gas in the presence of a hydrogenation catalyst such as nickel, palladium, platinum or copper. Can be done by

Hydrogen Storage Alloy Electrode Composition The binders (I) and (II) of the present invention are used in order to bind the components constituting the hydrogen storage alloy electrode (hereinafter referred to as “electrode”). It is called "composition".).
In this case, either one of the binders (I) and (II) can be used, or the binders (I) and (II) can be mixed and used. Furthermore, if necessary,
Other binders may be used in combination unless the intended effect of the present invention is impaired.

The electrode composition of the present invention contains a binder (I) and / or (II), a hydrogen storage alloy and a conductive material as main components.

Examples of the hydrogen storage alloy used in the electrode composition of the present invention include rare-earth alloys such as La-Ni alloys and Mm-Ni alloys, Laves phase alloys such as ZrV _0.4 Ni _1.6 and Ti alloys.
Ni, Ti ₂ Ni, Ti _1-x Zr _x Ni, Fe _0.94 Ti _0.96 Zr _0.04 N
b _0.04 , titanium-based materials such as TiFe _0.9 Mn _0.1 , TiMn _1.5 , Mg ₂ Ni
All known materials such as magnesium-based alloys such as CaNi ₅ and nickel-based materials such as CaNi ₅ can be used, but rare earth-based and Laves phase-based hydrogen storage alloys are preferable. In order to construct a fuel cell with excellent life and discharge capacity,
Of rare earth-based and Laves phase-based hydrogen storage alloys,
La-Ni based alloys or Mm-Ni based alloys are preferred. Examples of these La-Ni-based alloys or Mm-Ni-based alloys include
LaNi ₅ , LaNi _4.2 Al _0.8 , MmNi ₅ , MmNi _4.2 Al _0.8 , this Ni
Of MmNi _4.2-x Co _x Al _0.8 (provided that 0.
5 ≦ x ≦ 1.0), MmNi _4.5 Al _0.5 , MmNi _4.15 Fe _0.85 , Lm
Ni-based alloys (Lm is lanthanum-rich misch metal) and the like can be mentioned, but Mm-Ni-based alloys are particularly preferable in that the manufacturing cost can be reduced. The most preferred Mm-Ni based alloys are MmNi _4.2 Al _0.8 and MmNi _4.2-x Co.
_x Al _0.8 . Titanium-based alloys are generally used as hydrogen storage alloys other than rare earth-based and Laves phase-based alloys.
Passive oxides that hinder the diffusion of hydrogen atoms are generated on the surface of the hydrogen storage alloy particles, which tends to cause deterioration of battery characteristics.

The hydrogen storage alloy is usually used as fine particles or powder. The average particle size is 10-100
It is preferably in the range of μm. If the average particle size of the hydrogen storage alloy is less than 10 μm, deterioration phenomena such as electrode destruction and surface oxidation due to repeated charging / discharging reactions are likely to occur.
If it exceeds μm, the charge and discharge efficiency tends to decrease.

Further, examples of the conductive material used in the electrode composition of the present invention include conductive metals such as nickel, copper, silver, aluminum, or alloys thereof, carbon, and the like. Copper is preferred. These conductive materials may be blended in the electrode composition in the form of fine particles such as particles, powders, and fibers, or may be used by coating the surface of the hydrogen storage alloy.

[0021] When coating the hydrogen-absorbing alloy surface with the conductive material, for example, electroless plating, vacuum deposition method, metal infiltration method can be appropriately employed method such metallikon.
In this case, the conductive material is preferably nickel in order to suppress the oxidation reaction on the surface of the coated conductive material.

The mixing ratio of each component in the electrode composition of the present invention is 500 to 10,000 parts by weight of hydrogen storage alloy and 50 parts by weight of conductive material with respect to 100 parts by weight of the binder (I) and / or (II). ~ 3,000 parts by weight. A preferable blending ratio is 1,000 to 8,000 parts by weight of the hydrogen storage alloy, 100 to 2,000 parts by weight of the conductive material, and a blending amount of the conductive material per 100 parts by weight of the hydrogen storage alloy. Is preferably 10 to 35 parts by weight. When the content of the hydrogen storage alloy is less than 500 parts by weight with respect to 100 parts by weight of the binder (I) and / or (II), the electrode composition cannot obtain sufficient conductivity, The discharge capacity and charge / discharge characteristics of the battery used are also insufficient, and when it exceeds 10,000 parts by weight, the electrode composition has poor strength and flexibility, and the hydrogen storage alloy powder is likely to fall off. Furthermore, if the content of the conductive material is less than 50 parts by weight with respect to 100 parts by weight of the binder (I) and / or (II), the electron conductivity of the electrode composition will be insufficient, so that the chargeability will be insufficient. If the discharge efficiency is lowered and exceeds 3,000 parts by weight, the packing density of the hydrogen storage alloy is lowered and the discharge capacity is lowered.

When forming a hydrogen storage alloy electrode using the electrode composition of the present invention, it is usually used in a solution prepared by dissolving the above-mentioned binders (I) and / or (II) in a suitable solvent. A slurry is prepared by adding a hydrogen storage alloy and a conductive material, or a hydrogen storage alloy coated with a conductive material, and uniformly mixing them using, for example, a ball mill, a ribbon mixer, a pin mixer or the like.

Solvents that can be used to prepare a solution of the binder (I) and / or (II) include
For example, organic solvents such as n-hexane, n-heptane, n-octane, cyclohexane, benzene, toluene, xylene, ethyl acetate and trichloroethylene can be mentioned.

Production of Hydrogen Storage Alloy Electrode The method for producing a hydrogen storage alloy electrode using the electrode composition of the present invention is not particularly limited, but examples thereof include (a) the above slurry, For example, after molding into a predetermined shape by a doctor blade method, a calendar method or the like, the solvent is removed to obtain a dry sheet, and two or more dry sheets are used, and a metal plate having a plurality of through holes between the dry sheets. After sandwiching a current collector made of, etc., thermocompression bonding with a hot press or the like, a method of integrating the dry sheet and the current collector, (b) the slurry was directly coated on the current collector After that, the solvent is removed and the electrode composition and the current collector are integrated, (c) the slurry is directly applied onto a suitable substrate to remove the solvent, and then the mixture is applied by a hot press or the like. Press molding to form the electrodes, then the electrodes And a method for separating from the plate.

As the current collector, for example, a nickel wire mesh, a stainless wire mesh, or a punching board obtained by nickel-plating a perforated metal plate such as iron or stainless steel can be used. The surface of these current collectors is preferably preliminarily subjected to a grinding treatment by sandpaper, sandblasting or the like in order to improve the adhesion between the current collector and a dry sheet or the like.

The electrode produced by using the electrode composition of the present invention can be suitably used, for example, as a negative electrode of an alkaline secondary battery.

[0028]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but it will be apparent from the above description that the present invention is not limited to these Examples. Of the following Examples and Comparative Examples, Examples 1 to 4
And Comparative Examples 1 to 4 relate to the binder (I), and Examples 5 to 9 and Comparative Examples 5 to 8 relate to the binder (II). Example 1 The binder (I) shown in (1-1) of Table 1 was dissolved in toluene to prepare a 10 wt% solution. Using this solution as a hydrogen storage alloy, MmNi _3.5 Co _0.07 Al _0.8 (average particle size 75 μm) 1
00 parts by weight and copper powder as the conductive material (average particle size 35 μ
m) Evenly mixed with 25 parts by weight of binder (I),
Binder (I) for the total amount of hydrogen storage alloy and conductive material
A slurry containing 5% by weight of was prepared. This slurry is air-dried after forming a film by the doctor blade method,
A sheet-shaped electrode composition was obtained. Two sheets of this sheet-shaped electrode composition were used, and a 50-mesh nickel wire net was sandwiched between them as a current collector, and the temperature was 150 ° C and the pressure was 20 ° C.
A hydrogen storage alloy electrode was produced by thermocompression bonding at 0 Kg / cm ² . Then, the hydrogen storage alloy electrode was evaluated as follows. Discharge capacity A battery was constructed by using a hydrogen storage alloy electrode as a negative electrode, a sintered nickel plate as a positive electrode, a nylon nonwoven fabric as a separator, and a mixed aqueous solution of 5N potassium hydroxide and 1N lithium hydroxide as an electrolytic solution. This battery was repeatedly charged and discharged up to 500 times with a current of 0.6 coulomb under the condition of negative electrode regulation, and the charge and discharge cycle characteristics were examined.
In this case, charging was up to 120% and discharging was up to a final voltage of 0.9V. Mechanical destruction of electrodes and drop-off of alloy powder A battery (charge number = 10) after 500 times of charge / discharge of the battery was visually observed, and the degree of breakage and drop was evaluated according to the following criteria. ○ None, △ Half or less, × More than half. The evaluation results are shown in Table 2.

Examples 2 to 4 (1-3) of Table 1 (Examples 2 and 3) or (1-
5) In the same manner as in Example 1 except that the binder (I) shown in (Example 4) was used in the content ratio shown in Table 2 with respect to the total amount of them, the hydrogen storage alloy and the conductive material. Then, a hydrogen storage alloy electrode was prepared and evaluated. Table 2 shows the evaluation results
Shown in.

Comparative Examples 1 to 4 (1-2) (Comparative Example 1) and (1-
4) (Comparative example 2), (1-6) (Comparative example 3) or (1
-7) A hydrogen storage alloy electrode was prepared and evaluated in the same manner as in Example 1 except that the one shown in (Comparative Example 4) was used. The evaluation results are shown in Table 2.

[0031]

[Table 1]

[0032]

[Table 2]

As is clear from Tables 1 and 2, by using the hydrogen storage alloy electrode bound by the binder (I) of the present invention, the discharge capacity of the battery is high and the discharge capacity is High level is maintained even if charging and discharging are repeated many times. In addition, the electrodes are not mechanically broken and the hydrogen-absorbing alloy powder does not fall off despite the stress due to repeated charging and discharging. On the other hand, when the requirements of the present invention are not satisfied, depending on the shape of the block copolymer, the discharge capacity is significantly reduced by repeating charging and discharging a large number of times and the durability of the electrode is also insufficient. Ori (Comparative Example 3 and Comparative Example 4), discharge capacity, charge-discharge cycle characteristics,
The durability of the electrodes and the like are significantly reduced (Comparative Example 1
And Comparative Example 2).

Examples 5 to 6 The binder (II) shown in (2-1) of Table 3 was dissolved in toluene to prepare a 10 wt% solution. Using this solution as a hydrogen storage alloy, MmNi _3.5 Co _0.07 Al _0.8 (average particle size 75 μm) 1
00 parts by weight and copper powder as a conductive material (average particle size 35 μ
m) Evenly mixed with 25 parts by weight of binder (I),
Binder (II) for the total amount of hydrogen storage alloy and conductive material
Of 2% by weight (Example 5) and 5% by weight (Example 6), respectively, were prepared. A film was formed from these slurries by a doctor blade method and then air-dried to obtain a sheet-shaped electrode composition. Using two sheets of this sheet-shaped electrode composition, sandwiching a 50-mesh nickel wire mesh as a current collector between them, and thermocompression bonding at a temperature of 150 ° C. and a pressure of 200 Kg / cm ² to prepare a hydrogen storage alloy electrode. did. Next, the hydrogen storage alloy electrode was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 4.

Examples 7 to 9 (2-4) in Table 3 (Examples 7 and 8) or (2-
6) In the same manner as in Example 5, except that the binder (II) shown in (Example 9) was used at the content ratios shown in Table 4 with respect to the total amount of the binder, the hydrogen storage alloy and the conductive material. Then, a hydrogen storage alloy electrode was prepared and evaluated. Table 4 shows the evaluation results
Shown in.

Comparative Examples 5 to 8 (2-2) (Comparative Example 5) and (2-
3) (Comparative example 6), (2-5) (Comparative example 7) and (2
-7) A hydrogen storage alloy electrode was prepared and evaluated in the same manner as in Example 6 except that the one shown in (Comparative Example 8) was used. The evaluation results are shown in Table 4.

[0037]

[Table 3]

[0038]

[Table 4]

As is clear from Tables 3 and 4, by using the hydrogen storage alloy electrode bound by the binder (II) of the present invention, the discharge capacity of the battery is high and the discharge capacity is high. , High level is maintained even if charging and discharging are repeated many times. Moreover, the electrodes are not mechanically broken or the alloy powder is not dropped off, despite the stress caused by repeated charging and discharging. On the other hand, when the requirements of the present invention are not satisfied, depending on the shape of the block copolymer, the discharge capacity is significantly reduced by repeating charging and discharging a large number of times and the durability of the electrode is also insufficient. (Comparative Example 8), discharge capacity, charge / discharge cycle characteristics, electrode durability, etc. are all significantly reduced (Comparative Examples 5 to 7).

[0040]

The binder for hydrogen storage alloy electrode of the present invention is
It is possible to form an electrode that is easily soluble in an ordinary solvent and has excellent durability. Moreover, the battery using this electrode is excellent in discharge capacity, charge / discharge cycle characteristics, and the like. Therefore, the present invention largely contributes to improvement and improvement of high-performance batteries such as alkaline secondary batteries.

Claims (4)

[Claims] 1. A vinyl aromatic compound polymer block A ₁
And a conjugated diene polymer block B ₁ A ₁ -B
₁ block copolymer, A ₁ -B _1, further comprising a tilting block C ₁ to content gradually increased or decreased gradually vinyl aromatic compound consists of a vinyl aromatic compound and a conjugated diene
A block copolymer (i) selected from the group consisting of a -C ₁ block copolymer and an A ₁ -B ₁ -a ₁ block copolymer further containing a vinyl aromatic compound polymer block a _1. , The weight ratio of the vinyl aromatic compound and the conjugated diene is 5 to 6
0: 95-40, the total bond content of vinyl aromatic compounds in blocks A ₁ , C ₁ and a ₁ is 3 to 50% by weight of all monomers and the total bond content of vinyl aromatic compounds in block A ₁ is total. In the block copolymer (i) in which at least 3% by weight of the monomer and the vinyl bond content of the conjugated diene moiety in the block B ₁ exceeds 50 mol%, at least 30% of the double bond of the conjugated diene moiety is hydrogenated. A binder for a hydrogen storage alloy electrode, containing the hydrogenated conjugated diene-based block copolymer as described above. 2. A vinyl aromatic compound polymer block A ₂
And an A ₂ -B ₂ block copolymer consisting of a random copolymer block B ₂ of a vinyl aromatic compound and a conjugated diene, and the content of the vinyl aromatic compound consisting of a vinyl aromatic compound and a conjugated diene gradually increasing or decreasing. a ₂ -B ₂ -C ₂ block copolymers containing gradient block C ₂ further to, and vinyl aromatic compound polymer block a ₂
A block copolymer (ii) selected from the group consisting of A ₂ -B ₂ -a ₂ block copolymers further containing: wherein the vinyl aromatic compound and the conjugated diene have a weight ratio of 5 to 6
0: 95 to 40, bond content of the block A _2, C ₂ and a total bond content vinyl aromatic compound and in the block A ₂ by 3 to 25% by weight of the total monomers of a vinyl aromatic compound in ₂ total In the block copolymer (ii) in which at least 3% by weight of the monomer and the vinyl bond content of the conjugated diene moiety in the block B ₂ is 15 mol% or more, at least 30% of the double bond of the conjugated diene moiety is hydrogenated. A binder for a hydrogen storage alloy electrode, containing the hydrogenated conjugated diene-based block copolymer as described above. 3. A hydrogen storage alloy electrode composition comprising the binder for hydrogen storage alloy electrode according to claim 1 and / or 2. 4. 100 parts by weight of the binder for a hydrogen storage alloy electrode according to claim 1 and / or 500, 500 to 10,000 parts by weight of a hydrogen storage alloy, and conductive materials 50 to 3,0.
A hydrogen storage alloy electrode composition, characterized in that its main component is 00 parts by weight.