JP2002231248A - Molded article for paraffin-containing nickel-metal hydride battery and method for producing the same - Google Patents

Abstract

(57) [Summary] [Problem] To prevent collapse of a molded product electrode due to charge and discharge even when a molded product containing no current collecting support (conductive core material) is used as an electrode, Hydrogen storage for negative electrodes of alkaline secondary batteries with high discharge yield, high production yield when molding using alloy powder with a particle size of several tens of μm, with a small capacity reduction even if charging and discharging are repeated over a long period of time. Develop alloy compacts and compacted electrodes for nickel-hydrogen batteries. SOLUTION: A hydrogen storage alloy powder and paraffin are mixed and granulated, and the granulated powder is subjected to pressure molding, impregnated with a binder solution, and dried to obtain a molded electrode for a nickel-hydrogen battery. The hydrogen storage alloy powder and the binder are mixed and granulated, and the granulated powder is subjected to pressure molding, impregnated with dissolved paraffin, and dried to obtain a molded body for a nickel-hydrogen battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded product electrode and a method for producing the same, and more particularly, it does not collapse or deform even after repeated charging and discharging for a long period of time, and alloy corrosion proceeds even in a strong alkaline electrolyte. TECHNICAL FIELD The present invention relates to a molded electrode containing a hydrogen storage alloy which is difficult and has excellent discharge characteristics and contains paraffin as a binder, and a method for producing the same.

[0002]

2. Description of the Related Art A hydrogen storage alloy is an intermetallic compound capable of storing and releasing hydrogen electrochemically, and is mainly used as an electrode material for a negative electrode of an alkaline storage battery. This alloy is hydrogenated when the electrode is charged and dehydrogenated when the electrode is discharged, so that the volume of the alloy varies during charging and discharging. For this reason, the alloy alone caused electrode destruction accompanying the alloy destruction, and could not be used as an electrode. Therefore,
Generally, an electrode is used in which a mass of the hydrogen storage alloy is made into a powder having a constant particle size by mechanical pulverization or the like and applied to a current collecting support such as foamed nickel or punching metal.

FIG. 1 shows such a conventional electrode structure. In the conventional electrode, the binder 3 is used to prevent the hydrogen storage alloy powder 4 from falling off the current collecting support 1. Further, a conductive material 2 such as carbon or nickel powder is added in order to secure conductivity between the hydrogen storage alloy powder 4 and the current collecting support 1. Such a conventional electrode is manufactured by well kneading a hydrogen storage alloy powder together with a binder and a conductive material in an aqueous solution to form a slurry, coating and filling the current collecting support, and then forming.

On the other hand, to increase the electrode capacity of the negative electrode,
It is effective to increase the ratio of the hydrogen storage alloy to the entire electrode. As the best method, if an electrode can be manufactured only with a hydrogen storage alloy, a high-capacity nickel-metal hydride storage battery can be manufactured. The present inventors have proposed a method in which a hydrogen storage alloy having a specific particle size (a particle size such that hydrogenation and dehydrogenation of the hydrogen storage alloy do not proceed with fine powdering) is performed without a current collecting support or a binder. A porous body formed and sintered using the powder was produced. Since this porous sintered body does not include a material that does not contribute to hydrogen storage and release, such as a current collecting support and a binder, it has a high alloy filling amount and a high electrode capacity density. However, when manufacturing such a sintered body electrode, a dimensional change due to sintering accompanies. For this reason, electrodes or the like that require dimensional accuracy must be machined, and the alloy for the working margin is wasted. Therefore, it is desired to use a compact having no dimensional change, which does not waste alloy by processing, for the electrode.

[0005] In the case of a compact having no dimensional change, it is also required to produce a predetermined electrode with high dimensional accuracy, and a compact comprising only an alloy powder has been considered. In this method, almost no machining is required, so that almost no alloy loss occurs. However, when a compact electrode formed only by molding an alloy powder is used as an electrode, the bulk density of the compact is lower than the bulk density of the sintered body, and the electrode capacity density of the electrode is reduced accordingly. Here, the bulk density indicates the volume density including the pores of the sintered compact. However, countermeasures such as using an alloy having a high alloy capacity per unit weight (mAh / g) as a means of increasing the electrode capacity density of the compact, increasing the packing density by increasing the compaction pressure, and using a high alloy capacity per unit weight (mAh / g) Is mentioned.

[0006] A molded article containing no binder is:
The mechanical strength is weak, and the necessary minimum processing (for example, fine adjustment processing in the height direction) cannot be performed. In addition, when used as an electrode, the electrode collapses due to charging and discharging, the alloy powder constituting the molded electrode falls off, and the function as the electrode cannot be fulfilled. With respect to the press-formed body containing the hydrogen storage alloy powder and the binder, JP-A-1-119501, JP-A-8-7891, JP-A-9-31502, JP-A-4-181655, 1959-14
As described in Japanese Patent No. 7032, various studies have been made on hydrogen storage and alkaline secondary battery negative electrodes. However, when molding hydrogen-absorbing alloy powder finely pulverized to a particle size of several tens of μm, the moldability is poor without a binder, making it difficult to stably produce the alloy. The problem was that the capacity was reduced due to this.

[0007]

According to the present invention, even when a molded body containing no current collecting support (conductive core material) is used as an electrode, collapse of the molded body electrode due to charging and discharging can be prevented. , And a predetermined discharge capacity can be obtained.
An object of the present invention is to develop a molded article of a hydrogen storage alloy for an anode of an alkaline secondary battery having a high production yield when molding using an alloy powder having a particle diameter of m.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above problems, and as a result, have been determined to use a granulated powder obtained by kneading paraffin as a binder with a hydrogen storage alloy powder. Molded into a porous body having a bulk density, the binder is dispersed and contained in the voids and the alloy surface formed by contacting the hydrogen storage alloy powder, or the binder is kneaded with the hydrogen storage alloy powder By using the obtained granulated powder, a porous body having a predetermined bulk density is formed, and molten paraffin is dispersed and contained in voids and alloy surfaces formed by contacting the hydrogen storage alloy powders. It has been found that this problem can be solved.

The molded article of the hydrogen storage alloy for a negative electrode of an alkaline secondary battery according to the present invention is characterized in that the binder is formed in the voids formed by the contact of the hydrogen storage alloy granulated powder with the binder attached to the surface of the hydrogen storage alloy powder and the alloy surface. It is dispersed and contained, and preferably has a bulk density of 3.5 to 6.0 g / cm ³ . As a result, a molded product electrode having a good moldability yield, preventing the molded product electrode from collapsing due to charge and discharge, obtaining a predetermined discharge capacity, and suppressing an increase in internal pressure at the time of overcharging, and a method for manufacturing the same. I found it. In addition, an improvement in cycle life was also recognized because the elution of alloy components in a strong alkaline electrolyte can be suppressed by the presence of paraffin.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the hydrogen storage alloy powder used in the present invention will be described. The composition and production method of the hydrogen storage alloy mass used for the hydrogen storage alloy powder are not particularly limited, and hydrogen having a structure of AB _n (n is a positive number of 0.5 to 6) or a BCC-Laves structure A storage alloy or the like can be used.

[0011] Examples here, for the case of AB ₅ hydrogen storage alloy composition is described in detail. In AB ₅ type, A side element, a mixture of La alone or one or more rare earth elements and La,. Specifically, La, Mm
(Mm represents misch metal, part of La is Ce,
It is substituted with Pr, Nd or other rare earth elements. ), Lm (Lm represents La-rich Mm), or a mixture obtained by adding another rare earth element to a mixture thereof. Further, it is preferable that the rare earth element mixture contains La in an amount of 20 mol% or more. As the B-side element, (N
i) A composition consisting of _a (Co) _b (Al) _c (Mn) _d (M) _e is preferred. Here, a is a positive number of 1.8 to 6.0, b is a positive number of 0 or 1.0 or less, c is a positive number of 0 or 1.0 or less, and d is 0 or 1.0 or less. A positive number, e is 0 or 0.
It is a positive number of 5 or less. M is Si, Fe, Pb, Ti,
At least one element selected from the group consisting of Ca, Mg, Cu, In, Zn, Cr and Zr.

After mixing each metal element having the above composition, the mixture is heated to 1300 to 1600 ° C. in an atmosphere of an inert gas such as argon.
After the alloy is melted by using a high-frequency melting furnace or an arc melting furnace at the temperature described above, a hydrogen storage alloy lump is produced by cooling. In this case, a hydrogen storage alloy ribbon obtained by a quenching method such as a roll quenching method, or a spherical hydrogen storage alloy powder obtained by a disk atomization method may be used. If necessary, the heat treatment may be performed at a temperature of about 1000 ° C. in an inert atmosphere such as Ar.

Further, the hydrogen storage alloy mass is pulverized to produce a hydrogen storage alloy powder. As a pulverizing method, it is preferable to use a jet mill or an attritor, a jaw crusher, a roller mill, a ball mill, a brown mill, or the like to pulverize the particles to an average particle diameter of 100 μm or less in an inert gas atmosphere such as argon or nitrogen gas. Alternatively, pulverization may be performed by hydrogenation pulverization. In the case of a hydrogen storage alloy spherical powder obtained by a disk atomizing method, the powder may be used in the form of a spherical powder, or may be further pulverized to an average particle diameter of 20 μm or less. Further, after pulverization, surface treatment may be performed before use. If the average particle size of the hydrogen-absorbing alloy powder in this case exceeds 100 μm, pulverization accompanying charging and discharging is remarkable, and the compact may be collapsed.
It is preferably not more than 00 μm. Further, the thickness is preferably 5 μm or more in order to suppress corrosion and a decrease in capacity of the alloy surface due to the strong alkaline electrolyte.

The hydrogen storage alloy powder thus obtained is molded using paraffin as a binder to obtain a hydrogen storage alloy compact. The paraffin here has 16 to 40 carbon atoms.
Having a melting point of preferably at least 50 ° C, more preferably 55 to 70 ° C. In the case of paraffin having a melting point of less than 50 ° C., heat generated during charging and discharging dissolves the paraffin, lowers the binding force, and may lead to collapse of the electrode.

First, a hydrogen storage alloy powder is prepared by a semi-dry or wet granulation method to prepare a granulated powder having a binder attached thereto. As a result, the flowability of the powder is improved, and the uniform filling of the powder into the molding die becomes possible. Therefore, the density inside the molded body becomes uniform, and the production yield of the molded body at the time of molding can be improved. In this case, the shape of the granulated powder may be spherical or non-spherical. The average particle size of the granulated powder is controlled by the shape and size of the molded product to be produced, but is preferably 1 mm or less, and more preferably 100 to 500 μm, in consideration of the packing density in a molded product mold.

[0016] Regarding the method of preparing the granulated powder, paraffin is added to an aliphatic hydrocarbon such as hexane or the like.
A method of dissolving in a solvent of an aromatic hydrocarbon such as benzene or toluene to adjust to a predetermined concentration, spraying the solution and attaching it to the surface of the alloy powder to finish the alloys into granulated powder or a binder solution and alloy After kneading the powder, a method of evaporating the solvent to finish the granulated powder, or a method of heating while mixing the paraffin powder and the alloy powder to dissolve the paraffin as the binder and obtaining the granulated powder while adhering to the surface of the alloy powder And the like. Further, there is a method of finishing the granulated powder by spray granulation using a device such as a spray dryer. At this time, if the amount of paraffin added to the binder is more than 5% by weight in the final molded product, the charge / discharge function may be impaired due to poor conductive contact between the alloy particles, which is not preferable. In the case of such poor conductivity, a conductive agent must be added at the time of preparing the granulated powder or after preparing the granulated powder.
Powder and carbon powder. Conversely, if the amount of paraffin added as the binder is less than 0.5% by weight in the final molded product, the compactability of the granulated powder is deteriorated, the production yield of the molded product is reduced, and the effect of the paraffin addition is not sufficient. There are cases. Therefore, the addition amount is preferably about 0.5 to 5% by weight.

The binder which may be used in combination with paraffin is preferably a water-soluble binder.
Polyvinyl alcohol, carboxymethyl cellulose,
Methyl cellulose, cellulose such as hydroxypropyl cellulose, gelatin, polyethylene glycol, one or more of polyvinylpyrrolidone and the like can be used,
Water, alcohol, and the like can be used as the solvent.

The above-mentioned granulated powder is filled in a molding machine so as to have a desired shape.
Press molding at 5 ton / cm ² . The molded article of the present invention can be freely formed into a shape such as a cylinder, a prism, and a cylinder.

As described above, the molded article obtained by the above-described method has an improved production yield, but has a relatively low strength, and thus may be damaged when processed into a specified size or actually loaded into a battery can. Therefore, a binder solution impregnation step and a drying step are required. Furthermore, in order to prevent the molded article from collapsing due to charge and discharge, it is immersed in molten paraffin or a binder for 0.1 to 24 hours so that the total amount of the binder in the molded article is 0.5 to 5% by weight. By heating and drying at room temperature or at room temperature to 80 ° C., a binder is attached to or filled in the pores of the molded body, and the effect of improving the strength of the molded body can be obtained.

In this impregnation step, after forming a molded body using the granulated powder, a binder aqueous solution (solution) is sufficiently impregnated into the open pores in the molded body by utilizing the capillary phenomenon, and then the water (solvent) is formed. ) Is evaporated to adhere a binder (solute) to the surface of the alloy particles facing the pores inside the compact. According to this method, the electrical contact between the alloy particles is not impaired and the strength is increased by the binder, so that the strength of the compact can be increased.

Also, by using paraffin as a binder for preparing the granulated powder and as a binder for impregnating the compact after molding, elution of alloy components in the electrolyte is suppressed and contact with the electrolyte is suppressed. Extremely large average particle size of 20μ
It is possible to suppress corrosion of a molded electrode using an alloy powder having a large surface area of less than m. In addition, paraffin has a water-repellent effect, and a three-phase interface, which is said to rapidly perform a reaction to return oxygen gas generated during rapid charging to water on the surface of the molded electrode, is easily formed, and the internal pressure of the battery increases. Is considered to be able to be suppressed. It is considered that these facts make it possible to produce an alkaline secondary battery having excellent cycle life characteristics even when relatively quick filling is performed.

[0022]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.
However, the present invention is not limited to this. 1. Preparation of molded electrode for paraffin-containing Ni-hydrogen battery Example 1 Hydrogen storage alloy ingot manufactured in high-frequency melting furnace
(La 34% by weight, Ce 45% by weight, Pr 6% by weight, N
d15% by weight with respect to atomic ratio 1.0, Ni 3.75,
0.75 Co, 0.20 Mn, 0.30 Al)
Heat-treated in argon, uniform hydrogen storage alloy ingot
Was prepared. The alloy ingot is coarsely powdered in a nitrogen atmosphere.
Crushed. Furthermore, the average particle size was reduced to 500 μm using a brown mill.
To obtain a raw material for a jet mill. More books
In the invention, the gas pressure is 5.8 kgf / cm by the jet mill.^Two,
Dry crush the hydrogen storage alloy under nitrogen gas atmosphere,
Hydrogen storage alloy having a diameter of 15 μm and a particle size distribution width of 1 to 100 μm
A fine powder was obtained. Next, 7N-
Surface treatment in KOH to produce hydrogen storage alloy powder raw material
Was. Next, paraffin (mp58-60) made by Wako Pure Chemical
℃) dissolved in hexane and hydrogen storage
The solvent hexane was evaporated while mixing with the gold powder. So
Thereafter, the mixture was passed through a sieve having an opening of 300 μm to obtain granulated powder. this
In this case, the amount of paraffin attached is about 0.5% by weight of the granulated powder.
%. Next, 1.85 g of this granulated powder was weighed 20 mm.
And filling pressure of 6 ton / cm ^Two1mm thick molding
I got a body. This hydrogen storage alloy porous compact is polyvinyl
Alcohol (trade name C-25GP: manufactured by Shin-Etsu Chemical Co., Ltd.)
After immersing in a 5% by weight aqueous solution and defoaming for a certain period of time,
Leave for 1 day, take out, vacuum dry and use for Ni-hydrogen battery electrode
A molded article was obtained.

Example 2 A hydrogen-absorbing alloy powder produced in the same manner as in Example 1 was
Hexane solution of paraffin (mp 58-60 ° C)
The solvent hexane was evaporated while mixing with the liquid. That
Thereafter, the mixture was passed through a sieve having an opening of 300 μm to obtain granulated powder. This place
The amount of paraffin attached is about 5% by weight of the granulated powder.
You. Next, 1.85 g of the granulated powder was added to a mold having a diameter of 20 mm.
And molding pressure 6ton / cm ^TwoTo obtain a 1mm thick compact
Was. This hydrogen-absorbing alloy porous compact was
(C-25GP: Shin-Etsu Chemical Co., Ltd.) 5 weight
% Water solution, degassing for a certain period of time, then release for about 1 day
Place and take out and vacuum dry to form a molded body for Ni-hydrogen battery electrode
I got

Example 3 A hydrogen-absorbing alloy powder produced in the same manner as in Example 1 was
Methyl cellulose (trade name: SM-4000:
Shin-Etsu Chemical Co., Ltd.)
Water was evaporated. After that, it is crushed and the opening is 300μm
To obtain a granulated powder. Methyl cellulose in this case
Is about 0.5% by weight of the weight of the granulated powder. next,
1.85 g of this granulated powder is filled in a mold having a diameter of 20 mm and formed.
Form pressure 6ton / cm ^TwoThus, a molded product having a thickness of 1 mm was obtained. This water
Paraffin obtained by heating and melting porous storage alloy porous compacts
(Mp 58-60 ° C) and dipped for a certain time
It was taken out to obtain a molded body for a Ni-hydrogen battery electrode.

Comparative Example 1 Hydrogen storage alloy powder 1.8 produced in the same manner as in Example 1
5 g is filled in a mold having a diameter of 20 mm and the molding pressure is 6 ton / cm ^2.
Thus, a molded product having a thickness of 1 mm was obtained. This hydrogen-absorbing alloy porous molded body was treated with polyvinyl alcohol (trade name: C-25GP:
(Shin-Etsu Chemical Co., Ltd.), immersed in a 5% by weight aqueous solution, degassed for a certain period of time, left for about 1 day, taken out and dried in vacuum
A molded article for an i-hydrogen battery electrode was obtained.

Comparative Example 2 A hydrogen storage alloy powder produced in the same manner as in Example 1 was
Mix with polyvinyl alcohol aqueous solution at the ratio of
The solvent water was evaporated. Then crush and open
Through a 300 μm sieve to obtain granulated powder. Poly in this case
The amount of vinyl alcohol attached is about 0.5 weight of the granulated powder.
%. Next, 1.85 g of this granulated powder was 20 m in diameter.
m and filling pressure 6ton / cm ^TwoWith a thickness of 1mm
Obtained the form. This hydrogen storage alloy porous compact is
Alcohol (trade name: C-25GP: Shin-Etsu Chemical Co., Ltd.)
Immersed in a 5% by weight aqueous solution and defoamed for a certain period of time
After leaving it for about one day, take it out and dry it in a vacuum.
An electrode compact was obtained.

Comparative Example 3 A hydrogen-absorbing alloy powder produced in the same manner as in Example 1 was
Mix with polyvinyl alcohol aqueous solution at the ratio of
The solvent water was evaporated. Then crush and open
Through a 300 μm sieve to obtain granulated powder. Poly in this case
The amount of vinyl alcohol attached is about 3% by weight of the granulated powder.
It is. Next, 1.85 g of the granulated powder having a diameter of 20 mm was used.
Filling mold and forming pressure 6ton / cm ^Two1mm thick molded body
I got This porous article of hydrogen storage alloy is
Lucor (trade name: C-25GP: manufactured by Shin-Etsu Chemical Co., Ltd.) 5
Immersed in a 1% by weight aqueous solution and degassed for a certain period of time.
Leave it for a day, take it out, dry it in vacuum, and form it for Ni-hydrogen battery electrodes.
Obtained the form.

Comparative Example 4 A hydrogen-absorbing alloy powder produced in the same manner as in Example 1 was
Methyl cellulose (trade name: SM-4000:
Shin-Etsu Chemical Co., Ltd.)
Water was evaporated. After that, it is crushed and the opening is 300μm
To obtain a granulated powder. Methyl cellulose in this case
Is about 0.5% by weight of the weight of the granulated powder. next,
1.85 g of this granulated powder is filled in a mold having a diameter of 20 mm and formed.
Form pressure 6ton / cm ^TwoThus, a molded product having a thickness of 1 mm was obtained. This water
Polyvinyl alcohol (product)
Name C-25GP: manufactured by Shin-Etsu Chemical Co., Ltd.)
Immersed in air, degassed for a certain period of time, then left for about 1 day to take out
And dried under vacuum to obtain a molded body for a Ni-hydrogen battery electrode.

Example 4 A hydrogen storage alloy powder produced in the same manner as in Example 1 was
Hexane solution of paraffin (mp 58-60 ° C)
The solvent hexane was evaporated while mixing with the liquid. That
Thereafter, the mixture was passed through a sieve having an opening of 300 μm to obtain granulated powder. This place
The amount of attached paraffin is about 10% by weight of the granulated powder.
is there. Next, 1.85 g of the granulated powder was added to a 20 mm diameter gold.
Filling mold and forming pressure 6ton / cm ^TwoA 1mm thick compact
Obtained. This hydrogen storage alloy porous compact is
Coal (trade name: C-25GP: manufactured by Shin-Etsu Chemical Co., Ltd.)
About 1 day after immersion in a volume% aqueous solution
Leave it out, dry it in a vacuum and mold it for Ni-hydrogen battery electrodes
I got a body.

2. Measurement of Apparent Density The dimensions and weight of the molded bodies for Ni-hydrogen battery electrodes obtained in Examples 1 and 2 and Comparative Examples 1 to 4 were measured, and the apparent density per hydrogen storage alloy was calculated.

3. Comparison of Molding Yield In Examples 1 and 2 and Comparative Examples 1 to 4, the molding yields when manufacturing 20 pieces are compared.

[0032]

[Table 1]

Table 1 shows the molding yield by cracking of a thin molded article having a thickness of 1 mm in the molding step. Compared with Comparative Example 1, the molding yield of a molded article formed by adjusting granulated powder using a binder was improved, and in particular, paraffin 5 of Example 2 was used.
It can be seen that the molded body formed by filling with the weight% granulated powder has a particularly high molding yield. This is due to the fact that the uniform filling into the molding die was measured by using granulated powder and the binding effect of paraffin.

4. Measurement of Charge / Discharge Characteristics Using Negative-Regulated Open Battery In Examples 1, 2, and 4 and Comparative Examples 1 to 4, (10 × 1
0) It was cut out to a size of cm ² , sandwiched by a Ni-made felt as a current collector, wrapped with a Ni-made net (opening 100 mesh), welded with a Ni lead, and wrapped with a polypropylene non-woven fabric to form a negative electrode. In this case, the alloy weight is about 0.5 g and the capacity is about 150 mAh / g. On the other hand, as the positive electrode, two sintered nickel hydroxide electrodes (50 × 50) cm ² produced by a known method were used. A charge / discharge test was performed using an electrolyte of 6N-KOH and an Hg / HgO electrode as a reference electrode. The charge and discharge conditions were as follows: at a constant temperature of 25 ° C., the battery was charged at 60 mA per alloy weight for 7.5 hours, and then allowed to stand for 30 minutes, then Hg / Hg at 60 mA per alloy weight.
Discharge is performed until the voltage reaches 0.65 V with respect to the O electrode. Under these conditions, charge and discharge were repeated for 100 cycles, and the discharge capacity at the first cycle, the discharge capacity at the 10th cycle, and the capacity at the 100th cycle were measured. Table 2 shows the results.

[0035]

[Table 2]

5. Comparison of Elution of Alloy Components of Molded Article by Elution Test In Examples 1, Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 4, 10 × 10 cm was cut out and an elution test was performed under the following conditions. After immersion in 1 cc of 8N-KOH at 25 ° C. for 3 days, a 10 × 10 cm compact was taken out and
The eluted substance eluted and precipitated therein was converted into a solution by total acid decomposition, and the eluted substance was quantified by ICP analysis. Table 3 shows the results.

[0037]

[Table 3]

From the results of the charge / discharge test, the molded articles of Examples 1 and 2 using paraffin did not impair the initial activity as compared with the molded articles of PVA granulated powder of Comparative Examples 2 and 3, and a substantially predetermined discharge capacity was obtained. Have been. In addition, according to the results of the dissolution test, Example 1 using paraffin during granulation and Example 3 using paraffin for impregnation suppressed the dissolution of alloy components from the comparative example. It can be seen that the progress of corrosion can be prevented in the used Ni-hydrogen battery. From these facts, it can be said that the molded article is a long-life molded article that does not collapse or deform even after repeated charging and discharging for a long period of time, and that alloy corrosion hardly progresses even in a strongly alkaline electrolyte.

[0039]

As described above, according to the present invention, the production yield when molding the binder-attached granulated powder is improved, and even if charge and discharge are repeated for a long time, collapse and deformation do not occur.
It is possible to provide a long-life molded body for a Ni-hydrogen battery in which alloy corrosion hardly progresses even in a strong alkaline electrolyte. In addition, the increase in battery internal pressure during overcharge due to the water-repellent effect of paraffin can be expected.

[Brief description of the drawings]

FIG. 1 shows a conventional electrode structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Current collection support (conductive core) 2 Conductive agent 3 Binder and hole 4 Hydrogen storage alloy powder

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 10/30 H01M 10/30 Z (72) Inventor Satoshi Shima 2-5-1 Kitafu, Takefu City, Fukui Prefecture F-term in Shin-Etsu Kagaku Kogyo Co., Ltd. Magnetic Materials Research Laboratories (reference)

Claims (5)

[Claims] 1. A molded article for a nickel-hydrogen battery comprising a hydrogen storage alloy and paraffin. 2. The molded article for a nickel-metal hydride battery according to claim 1, wherein the paraffin is contained in an amount of 0.5 to 5% by weight. 3. A nickel-hydrogen battery using the molded product for a nickel-hydrogen battery according to claim 1. 4. A method for producing a molded body for a nickel-hydrogen battery, comprising mixing and granulating a hydrogen storage alloy powder and paraffin, press-molding the granulated powder, impregnating in a binder solution, and drying. 5. A method for producing a molded body for a nickel-hydrogen battery, comprising mixing and granulating a hydrogen storage alloy powder and a binder, press-molding the granulated powder, impregnating with melted paraffin, and drying.