JPH06102802B2 - Material for hydrogen storage alloy and method for producing the same - Google Patents

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 material and a method for producing the same. More specifically, the present invention relates to a material for hydrogen storage alloy, which has excellent hydrogen absorption / desorption characteristics immediately after production and can retain the characteristics in a powder state for a long time, and a method for producing the same. The hydrogen storage alloy has a property of absorbing hydrogen by decreasing the ambient temperature or increasing the ambient hydrogen pressure, and releasing hydrogen by increasing the ambient temperature or decreasing the ambient hydrogen pressure, Secondary energy
It plays an important role in storing hydrogen as hydrogen. This hydrogen storage alloy has uses as a medium for storing and transporting hydrogen, an energy conversion medium, a catalyst, and the like, as well as a nickel-hydride battery and the like. In particular, nickel-hydride batteries are attracting attention as a safe alternative to the cadmium used in nickel-cadmium batteries, which are widely used as a portable power source for electronic devices, because of their concern about the safety of the human body. Are gathering. The material for hydrogen storage alloy according to the present invention is used as a hydrogen storage alloy as a powder as it is or after being molded, and it has excellent hydrogen absorption / desorption characteristics immediately after production and has a long time in the powder state. Since it can be retained for a period of time, it is suitable for the various applications described above, particularly for nickel-hydride batteries.

[0002]

2. Description of the Related Art Materials for hydrogen storage alloys absorb and release hydrogen by reacting a metal (including alloy) with hydrogen to form a metal-hydrogen compound or returning to a metal and hydrogen. When the reaction between the metal and hydrogen is repeated many times, the material for hydrogen storage alloy is subdivided,
Splitting may occur. As a result, the hydrogen storage alloy material has a large contact area with hydrogen, so
The release effect is increased. However, on the other hand, for example, when such a hydrogen storage alloy material is used in a nickel-hydride battery, the hydrogen storage alloy material in which subdivision or splitting has occurred easily falls off from the electrode support. However, there is a problem that the battery capacity decreases. Further, in the hydrogen storage alloy material in which the fragmentation or the splitting has occurred, the new surface exposed due to the occurrence of the segmentation or the splitting is oxidized, so that the conductivity (including the thermal conductivity-the same applies hereinafter). There is a problem in that Further, for example, when the hydrogen storage alloy material is used as an energy conversion medium, there is a problem that the filter is clogged with the subdivided hydrogen storage alloy material.

Therefore, as one method for improving the mechanical strength and conductivity of the hydrogen storage alloy material, electroless plating is used to deposit copper and / or nickel on the surface of the hydrogen storage alloy powder. A method of coating to obtain a hydrogen storage alloy material is known (Japanese Patent Publication No. 3-12121).
As another method, a powder for hydrogen storage alloy and a copper fine powder or a nickel fine powder are mixed with a dry type with mechanical energy, and the surface of the hydrogen storage alloy powder is bonded and coated with the copper fine powder or the nickel fine powder. There is known a method for obtaining a material for hydrogen storage alloy (JP-A-3-10002).

[Problems to be Solved by the Invention]

However, since the former method involves plating treatment, there is a problem that not only is it time-consuming to adjust and manage the plating solution, but also many treatment steps such as washing and drainage result in high cost. Further, the hydrogen storage alloy powder obtained by this method has a problem that the hydrogen absorption / desorption characteristics are poor because the hydrogen absorption / desorption action is performed only through the pinhole portion of the plating. . Further, when the film plated on the surface of the powder for hydrogen storage alloy is a copper film, it is easily oxidized, so that there is a problem that deterioration of hydrogen absorption / desorption characteristics with time progresses rapidly.

In the latter method, fine powder that is easily oxidized is used as the metal powder for coating the powder for hydrogen storage alloy, and when the powder for hydrogen storage alloy and copper fine powder or nickel fine powder are mixed and stirred. The surface of the hydrogen storage alloy powder, the copper fine powder, or the nickel fine powder is scraped off or divided due to the friction between the hydrogen storage alloy powder, the copper fine powder, or the nickel fine powder. , A new surface is exposed and there is a great risk that it will be oxidized. Therefore, the material for hydrogen storage alloy obtained by this method is
There is a problem that the release characteristics are inferior. Further, since the hydrogen storage alloy material, the hydrogen storage alloy powder, the copper fine powder, or the nickel fine powder is exposed, it is easily oxidized and the hydrogen absorption / desorption characteristics deteriorate with time. is there.

[0006] Therefore, the present inventor repeatedly conducted a number of experiments for the purpose of improving the invention according to Japanese Patent Laid-Open No. 3-10002, which has the advantage of the dry method, and as a result, finally achieved the intended purpose. The inventors have completed a possible hydrogen storage alloy material and a method for producing the same according to the present invention.

[0007]

That is, the material for hydrogen storage alloy according to the present invention comprises a conductive powder and a cuprous oxide powder which are jointly coated on the surface of the powder for hydrogen storage alloy, and the whole is made of an antioxidant. It is characterized by being coated. The method for producing a material for a hydrogen storage alloy according to the present invention is roughly classified into a case where the powder for a hydrogen storage alloy used has a large particle size and a case where it does not.

The particle size of the hydrogen storage alloy powder used is about 1
In the case of a fine powder of about 00 microns, it is not necessary to pulverize the powder for hydrogen storage alloy, so the powder for hydrogen storage alloy, the conductive powder, the cuprous oxide powder and the antioxidant are added to a high energy-type stirrer. From the initial stage, the conductive powder and the cuprous oxide powder are bonded and coated on the surface of the powder for hydrogen storage alloy by using the compressive force and the shearing energy at the time of mixing and stirring by the medium-high speed rotation from the initial stage, and the granulation is performed while granulating. The material for a hydrogen storage alloy according to the present invention is manufactured by granulating and coating the whole with an antioxidant.

The finer the hydrogen storage alloy powder, the more easily the oxidation proceeds. Therefore, it is easier to store the hydrogen storage alloy powder if a coarse powder having a particle size of about 500 microns or more is used as much as possible. Therefore, in such a case, the powder for hydrogen storage alloy, the conductive powder, the cuprous oxide powder and the antioxidant are put in a high energy-type stirrer, and in the initial stage, the grinding force at the time of mixing and stirring by low speed rotation is adjusted. The powder for hydrogen storage alloy and the conductive powder are pulverized by using the conductive powder and the conductive powder on the surface of the powder for hydrogen storage alloy by using compressive force and shearing energy at the time of mixing and stirring by medium-high speed rotation in the next step. The material for hydrogen storage alloy according to the present invention is produced by jointly coating cuprous oxide powder, sizing while granulating, and coating the whole with an antioxidant.

The hydrogen storage alloy powder used in the present invention includes MmNi _3.5 Co _0.7 Al _0.8 and LaN.
i ₅ , TiCo _0.5 Mn _0.5 , TiCo _0.5 Fe _0.5 ,
MmNi _4.5 Mn _0.5 , MmNi _4.5 Al _0.5 (Mm
Indicates a mesh metal, and a mixture of rare earths) or the like can be used. The particle size of this hydrogen storage alloy powder is
5-500 microns are preferred. When it is less than 5 microns, the powder for hydrogen storage alloy adheres to the machine wall due to mechanical compressive force, while when it exceeds 500 microns, the specific surface area of the powder for hydrogen storage alloy becomes large due to pulverization. This is because a large amount of conductive powder must be used as a result.

The conductive powder is used to improve the mechanical strength and conductivity of the hydrogen storage alloy powder, and copper powder, nickel powder, cobalt powder, and silver powder can be used. Two or more kinds of these conductive powders can be used in combination. The particle size of the conductive powder is 1 to 4
5 microns is preferred. The reason is that if the particle size is less than 1 micron, the bonding coating layer of the conductive powder and the cuprous oxide powder bonded to the surface of the hydrogen storage alloy powder becomes too dense and the hydrogen absorption / desorption characteristics are increased. On the other hand, when it exceeds 45 μm, the joint coating layer of the conductive powder and the cuprous oxide powder becomes too rough and the mechanical strength and the conductivity decrease. The amount of conductive powder added is 6
-10 parts by weight is preferable. When the amount is less than 6 parts by weight, the hydrogen storage alloy powder has an irregular shape, so that the covering effect is insufficient, while when the amount is more than 10 parts by weight, it is considered as a conductive powder. This is because the coating layer with the cuprous oxide powder becomes too thick and the absorption / desorption rate of hydrogen becomes slow.

Of the conductive powders, copper powder is the most practical. This is because the copper powder is rich in malleability and can be bonded to the surface of the powder for hydrogen storage alloy even with a relatively weak compressive force and shearing energy. Among such copper powders, electrolytic copper powder is particularly preferable. This is because the electrolytic copper powder has a dendritic shape and is easily crushed during mixing and stirring, so that the periphery of the hydrogen storage alloy powder can be jointly coated with fine copper powder.

The electrolytic copper powder has a particle size of 5 μm to 4 μm.
5 micron, specific surface area 2000 cm ² / g ~ 7000 cm ²
The range of / g is preferable. If the particle size is less than 5 microns or the specific surface area exceeds 7000 cm ² / g, the bonding coating layer of the conductive powder and the cuprous oxide powder formed on the surface of the hydrogen storage alloy powder becomes dense. If the particle size exceeds 45 microns or the specific surface area is less than 2000 cm ² / g, the bonding coating layer of the conductive powder and the cuprous oxide powder will be deteriorated. This is because it becomes too coarse and the mechanical strength and conductivity decrease.

When the powder for hydrogen storage alloy used in the present invention and the conductive powder are mixed and stirred with a high energy type stirrer, the conductive powder is bonded and coated on the surface of the powder for hydrogen storage alloy. The distance between the conductive powder particles becomes large, which is not sufficient to improve the mechanical strength and conductivity of the hydrogen storage alloy material. Therefore, in order to make up for this point, cuprous oxide powder is mixed in the present invention. Since this cuprous oxide powder has a small particle size, when mixed with the powder for hydrogen storage alloy and the conductive powder, it becomes a mixed state with the conductive powder and is bonded to the surface of the powder for hydrogen storage alloy and the conductive powder. Bonding is also performed on the surface of the hydrogen storage alloy powder which does not exist, and a bonding coating layer is formed on the surface of the hydrogen storage alloy powder. When the material for hydrogen storage alloy is used as a battery, the cuprous oxide powder has a positive potential (−0.8 V with respect to the mercury oxide reference electrode, −0 V relative to the mercury oxide reference electrode) during charging. By applying an electric current of 0.92 V) in the electrolytic solution, it is reduced to copper and becomes integrated with the conductive powder, which is useful for improving the mechanical strength and conductivity of the hydrogen storage alloy material.

The particle size of the cuprous oxide powder is preferably 0.5 to 2 microns. The reason is that when the thickness is less than 0.5 micron, the coating layer of the conductive powder and the cuprous oxide powder becomes too dense and the absorption / desorption rate of hydrogen becomes slow, while when it exceeds 2 micron. The reason is that reduction of cuprous oxide to copper is less likely to occur during charging. The addition amount of the cuprous oxide powder is preferably 1 to 10 parts by weight. The reason is that if the amount is less than 1 part by weight, the effect of addition is not obtained, and if the amount exceeds 10 parts by weight, when the hydrogen storage alloy material is used as a battery, usually, a complete battery capacity is obtained by initial charging. Because you cannot get it.

The antioxidant prevents oxidation of the powder for the hydrogen storage alloy and the conductive powder at the time of manufacturing the material for the hydrogen storage alloy, and also for the material for the hydrogen storage alloy or the hydrogen storage alloy formed by using the material. It is used for the purpose of preventing oxidation during storage and reacts with the powder for hydrogen storage alloy to form an antioxidant film. As the antioxidant, boron-
Nitrogen-based antioxidant (polyoxyethylene-dis-1.
2.3-Trihydroxypropanepolide 1 delta heptadecane-1-carboxylate / N polyoxyethylene-1-aminohexadecane compound, etc., titanate antioxidant (isopropyl triisostearoyl titanate)
Etc.), aluminum-based antioxidants (acetoalkoxyaluminum diisopropylate, etc.), silane-based antioxidants (vinyltriethoxysilane, etc.), etc., and these may be used alone or in combination of two or more. used.

When the hydrogen storage alloy material obtained according to the present invention is used in a nickel-hydride battery, the hydrogen storage alloy material is used in an alkaline solution. Nitrogen-based antioxidants or titanate-based antioxidants, particularly boron-nitrogen-based antioxidants are preferred. This is because when a boron-nitrogen-based antioxidant is used, a nitride is formed on the surface of the material for hydrogen storage alloy, which serves as a strong antioxidative coating, and the oxidation of the powder for hydrogen storage alloy and the conductive powder. This is because it can be prevented. In addition, the boron-nitrogen antioxidant is superior in conductivity to other antioxidants. The addition amount of the antioxidant is preferably 0.1 to 1 part by weight. 0.1
This is because if it is less than 1 part by weight, the effect of addition is not obtained, and if it exceeds 1 part by weight, the electrochemical reaction is hindered.

As the high energy type agitator, for example,
It is also possible to use a ball mill, a vibration mill, a breaker, an attritor, a medium agitating mill, or the like. However, the mechanofusion (manufactured by Hosokawa Micron Co., Ltd.), which has a large compressive force and shearing energy at the time of mixing and stirring and produces little fine powder, is the most suitable.

When using the coarse powder for hydrogen storage alloy, the high energy type agitator is rotated at a low speed in the initial stage and is rotated at a medium and high speed in the next stage. By the initial low speed rotation, the pulverizing force of the high energy type agitator sufficiently acts to pulverize the hydrogen storage alloy powder and the conductive powder. The crushing force of the high energy type agitator is suppressed by the subsequent medium and high speed rotation, and the compressive force and the shearing energy act to bond and coat the surface of the powder for hydrogen storage alloy with the conductive powder and the cuprous oxide powder. . Further, by mixing and stirring by medium-high speed rotation, the entire powder for hydrogen storage alloy, which is granulated while being granulated and bonded and coated with the conductive powder and the cuprous oxide powder, is coated with the antioxidant. If the method for producing a material for a hydrogen storage alloy according to the present invention is carried out with one high energy-type stirrer, the cost can be reduced. When using a fine powder for hydrogen storage alloy, it is not necessary to use the crushing force of the stirrer, so high energy
The mold stirrer is rotated at medium to high speed from the beginning. Here, the low speed rotation is 200 to 400 (rpm), and the medium and high speed rotation is 600 to 1200 (rpm), preferably 700.
Means ~ 1000 (r.p.m.).

When carrying out the method for producing a material for a hydrogen storage alloy according to the present invention, mixing and stirring are carried out in a non-oxidizing atmosphere such as argon gas or nitrogen gas, or a liquid such as water or alcohol. With this, it is possible to completely prevent the oxidation of the hydrogen storage alloy material and the conductive powder. Usually, even if the hydrogen storage alloy material is produced under the above conditions while paying attention to the prevention of oxidation, if the hydrogen storage alloy powder or its coating layer is exposed, when the hydrogen storage alloy material is taken out from the stirrer. When exposed to the atmosphere, oxidation immediately starts on the surface. However, in the present invention, the hydrogen-absorbing alloy powder and the bonding coating layer of the conductive powder and the cuprous oxide powder on the surface of the hydrogen-absorbing alloy are coated with an antioxidant, so that they are oxidized even if taken out into the air after production. There is no fear of doing it.

[0021]

In the material for hydrogen storage alloy according to the present invention, conductive powder and cuprous oxide powder are bonded and coated on the surface of the powder for hydrogen storage alloy, and the whole is further coated with the antioxidant.
Further, since the new surfaces of the powder for hydrogen storage alloy and the conductive powder which are temporarily exposed during the manufacturing process are also coated with the antioxidant, they are not oxidized.

The method for producing a material for a hydrogen storage alloy according to the present invention in the case of using a fine powder for a hydrogen storage alloy comprises a powder for a hydrogen storage alloy, a conductive powder, a cuprous oxide powder and an antioxidant at high energy. By putting it in a mold stirrer and rotating it at medium to high speed from the initial stage, the conductive powder and cuprous oxide powder are plastically deformed by utilizing the compressive force and shearing energy at the time of mixing and stirring, and the hydrogen storage alloy. The surface of the powder for use is firmly bonded and coated. At the same time, the granules are sized while being granulated by mixing and stirring to coat the entire powder for hydrogen storage alloy on which the conductive powder and the cuprous oxide powder are jointly coated with the antioxidant.

On the other hand, the method for producing a material for a hydrogen storage alloy according to the present invention when a coarse powder for a hydrogen storage alloy is used,
Powder for hydrogen storage alloy, conductive powder, cuprous oxide powder and antioxidant are put in a high energy-type stirrer, by performing low speed rotation in the initial stage, utilizing the crushing force during mixing and stirring, hydrogen The storage alloy powder and the conductive powder are crushed. At this time, a new surface of the hydrogen storage alloy powder and the conductive powder is exposed by the pulverization, and at the same time, the new surface is coated with the antioxidant. Then, in the next stage, by performing a medium-high speed rotation, the conductive powder and the cuprous oxide powder are plastically deformed by utilizing the compressive force and the shearing energy at the time of mixing and stirring, and the powder for hydrogen storage alloy is The surface is strongly bonded and coated. At the same time, the granules are sized while being granulated by mixing and stirring to coat the entire powder for hydrogen storage alloy on which the conductive powder and the cuprous oxide powder are jointly coated with the antioxidant.

[0024]

EXAMPLES Next, the present invention will be described in detail based on Examples, Experimental Examples and Comparative Examples. Example 1 Powder for hydrogen storage alloy having an average particle size of 250 microns [MmN
i _3.5 Co _0.7 Al _0.8 : However, Mm is misch metal, and 100 parts by weight of a mixture of rare earths is added to 100 parts by weight of electrolytic copper powder [average particle size: 10 μm, specific surface area: about 5000 cm ^2]
/ G], cuprous oxide powder [average particle size 0.5 micron: manufactured by Nisshin Chemical Co., Ltd.], and boron-nitrogen antioxidant [EN-
130: trade name: manufactured by Toho Chemical Industry Co., Ltd.] in the proportions shown in Table 1 by MechanoFusion [Hosokawa Micron Co., Ltd.]
Manufactured at the same time, and the number of revolutions is 800 (rp.
In (m), mixing and stirring were performed for 30 minutes. As a result, electrolytic copper powder and cuprous oxide powder were bonded and coated on the surface of the hydrogen storage alloy powder, and the whole was further coated with the above antioxidant,
A hydrogen storage alloy material having a maximum particle size of 355 microns and an average particle size of 60 microns was obtained.

Experimental Example 1 Hydrogen storage alloy material obtained in Example 1 and 3 wt% PTFE
A resin (D-2: trade name: manufactured by Daikin Industries, Ltd.) is mixed to form a sheet of 3 × 4 × 0.3 cm, which is sandwiched between nickel nets and cold pressed into a sandwich to form a negative electrode. did. Using a sintered nickel oxide electrode for the positive electrode, a test battery using a 6N-potassium hydroxide solution as an electrolytic solution was assembled. The amount of hydrogen storage alloy in the negative electrode was 4 g, and the capacity was 1200 mA.
-H, and all the test batteries were of the negative electrode regulation type in which the battery capacity depended on the negative electrode capacity. These test batteries were charged at a charging current of 400 mA in a thermostatic chamber at a temperature of 20 degrees.
After charging for 3 hours at rest for 0.5 hour, discharge current 20
An experiment in which charge and discharge were repeated 50 times in a cycle of discharging at 0 mA until the voltage dropped to 0.8 V was performed, and the maximum discharge capacity (mA · h / g) of the test battery was measured. The results are shown in Table 1.

Example 2 Powder for hydrogen storage alloy having an average particle size of 600 microns [MmN
i _3.5 Co _0.7 Al _0.8 : However, Mm is misch metal, and 100 parts by weight of a mixture of rare earths is added to 100 parts by weight of electrolytic copper powder [average particle size: 10 μm, specific surface area: about 5000 cm ^2]
/ G], cuprous oxide powder [average particle size 0.5 micron: manufactured by Nisshin Chemical Co., Ltd.], and boron-nitrogen antioxidant [EN-
130: trade name: manufactured by Toho Chemical Industry Co., Ltd.] in the proportions shown in Table 1 by MechanoFusion [Hosokawa Micron Co., Ltd.]
Manufactured at the same time, and while the argon gas is introduced from a commercially available argon gas cylinder, the rotation speed is 300 (rp.
m) and mixed and stirred for 5 minutes, and then rotated at a speed of 800 (r.
p. In (m), mixing and stirring were performed for 30 minutes. As a result, electrolytic copper powder and cuprous oxide powder were jointly coated on the surface of the hydrogen storage alloy powder, and the whole was further coated with the above-mentioned antioxidant. An alloy material was obtained.

Experimental Example 2 An experiment was conducted in the same manner as in Experimental Example 1 except that the hydrogen storage alloy material obtained in Example 2 was used. The results are shown in Table 1.

Comparative Example 1 Powder for hydrogen storage alloy [MmN having an average particle size of 250 μm]
i _3.5 Co _0.7 Al _0.8 : However, Mm represents misch metal, 100 parts by weight of a mixture of rare earths, and 100 parts by weight of electrolytic copper powder [average particle size: 50 μm, specific surface area: about 1500 cm ^2]
/ G] in the MechanoFusion [manufactured by Hosokawa Micron Co., Ltd.] at the rate shown in Table 1 simultaneously, while flowing argon gas from a commercially available argon gas cylinder at a rotation speed of 800 (rpm) for 30 minutes. Mixing and stirring were performed.
As a result, the surface of the hydrogen storage alloy powder was jointly coated with electrolytic copper powder, the maximum particle size was 350 μm, and the average particle size was 70 μm.
A micron hydrogen storage alloy material was obtained.

Comparative Experimental Example 1 An experiment was conducted in the same manner as in Experimental Example 1 except that the hydrogen storage alloy material obtained in Comparative Example 1 was used. The results are shown in Table 1.

[0030]

[Table 1] As is clear from Table 1, in each of Experimental Examples 1 (1) to (11) and Experimental Examples 2 (1) to (5), the maximum discharge capacity 22
A value of 0 (mA · h / g) or higher was obtained. This is because the new surface of the powder for hydrogen storage alloy and the electrolytic copper powder generated during the production of the material for hydrogen storage alloy is coated with an antioxidant at the same time as it is exposed, and this coating layer forms a nitride to form a strong oxide. It is recognized that it is due to the interaction of the fact that it became an prevention film and that the cuprous oxide powder that was jointly coated with the electrolytic copper powder on the surface of the hydrogen storage alloy powder was electrochemically reduced to copper during charging. .

Example 3 and Experimental Example 3 The same experiment as in Experimental Example 1 was conducted using the material for hydrogen storage alloy obtained in the same manner as in Example 1 except that the composition shown in Table 2 was changed. The results are shown in Table 2.

[0032]

[Table 2]

Example 4 and Experimental Example 4 The same experiment as in Experimental Example 1 was conducted using the powder for hydrogen storage alloy obtained in the same manner as in Example 1 except that the composition shown in Table 3 was changed. The results are shown in Table 3.

Comparative Example 2 and Comparative Experimental Example 2 The same experiment as in Experimental Example 4 was conducted using the powder for hydrogen storage alloy obtained in the same manner as in Example 1 except that no antioxidant was used. The results are shown in Table 3.

[0035]

[Table 3]

Example 5 and Experimental Example 5 1 part of electrolytic copper powder was added to 100 parts by weight of powder for hydrogen storage alloy.
Using a hydrogen storage alloy material obtained in the same manner as in Example 1 except that 0 part by weight, 3 parts by weight of cuprous oxide powder and 0.3 part by weight of boron-nitrogen antioxidant [EN-130] were used. An experiment similar to that of Experimental Example 1 was performed. The results are shown in Table 4.

[0037]

[Table 4] As is clear from Table 4, the maximum discharge capacity did not deteriorate even after 30 days. It is recognized that this is because the antioxidant reacts with the powder for hydrogen storage alloy to form a conductive antioxidant film.

Comparative Example 3 and Comparative Experimental Example 3 100 parts by weight of the powder for hydrogen storage alloy was mixed with 1 part of electrolytic copper powder.
Experimental Example 5 using the hydrogen storage alloy material obtained in the same manner as in Example 1 except that 0 parts by weight and 3 parts by weight of cuprous oxide powder were used.
The same experiment was performed. The results are shown in Table 5.

[Table 5]

Example 6 and Experimental Example 6 The same experiment as in Experimental Example 1 was conducted using the hydrogen storage alloy material obtained in the same manner as in Example 1 except that the composition shown in Table 6 was changed. The results are shown in Table 6.

[0040]

[Table 6] As is clear from Table 6, when the copper powder is replaced with the cobalt powder, the discharge capacity is improved as compared with the copper powder alone. It is considered that this is because cobalt is deposited as fine particles on the surface of the hydrogen storage alloy powder by the dissolution and precipitation reaction in the electrolytic solution, and the same effect as that of the cuprous oxide powder is brought about.

Experimental Example 7 An experiment similar to Experimental Example 1 was conducted using the hydrogen storage alloy material obtained in the same manner as in Example 1 except that the composition shown in Table 7 was changed. The results are shown in Table 7.

[Table 7] As is clear from Table 7, when 1 to 5 parts by weight of the copper powder is replaced with the silver powder, a higher discharge capacity can be obtained than when the copper powder alone is used. It is recognized that this is because the silver powder is more malleable than the copper powder, so that the silver powder is firmly bonded to the surface of the hydrogen storage alloy powder.

[0042]

The material for hydrogen storage alloys according to the present invention has the surface of the powder for hydrogen storage alloys which is coated with the conductive powder and the cuprous oxide powder by bonding, and is further coated with the antioxidant as a whole. The new surfaces of the powder for hydrogen storage alloy and the conductive powder that are temporarily exposed during the manufacturing process are not oxidized and are also coated with the antioxidant. Therefore, this material for a hydrogen storage alloy is not only excellent in hydrogen absorption / desorption characteristics immediately after production, but also can retain the characteristics in a powder state for a long period of time.

In the method for producing a material for a hydrogen storage alloy according to the present invention when a fine powder for a hydrogen storage alloy is used, the powder for a hydrogen storage alloy, the conductive powder, the cuprous oxide powder and the antioxidant are treated with high energy. -By putting in a type stirrer and rotating at medium to high speed from the initial stage, the compressive force and shearing energy at the time of mixing and stirring are used to cause plastic deformation of the conductive powder and cuprous oxide powder, and hydrogen storage. The surface of the alloy powder is firmly bonded and coated. At the same time, the granules are sized while being granulated by mixing and stirring, and the entire powder for hydrogen storage alloy on which the conductive powder and the cuprous oxide powder are jointly coated is coated with the antioxidant. Further, in the method for producing a hydrogen storage alloy material according to the present invention when using a coarse hydrogen storage alloy powder, the hydrogen storage alloy powder, a conductive powder,
By putting the cuprous oxide powder and the antioxidant in a high energy-type stirrer and performing high-speed rotation from the initial stage,
By utilizing the compressive force and shearing energy at the time of mixing and stirring, the conductive powder and the cuprous oxide powder are plastically deformed to firmly bond and coat the surface of the powder for hydrogen storage alloy. At the same time, the granules are sized while being granulated by mixing and stirring, and the entire powder for hydrogen storage alloy on which the conductive powder and the cuprous oxide powder are jointly coated is coated with the antioxidant. Then, in the next stage, by performing a medium-high speed rotation, the conductive powder and the cuprous oxide powder are plastically deformed by utilizing the compressive force and the shearing energy at the time of mixing and stirring, and the powder for hydrogen storage alloy is The surface is firmly bonded and coated. At the same time, the granules are sized while being granulated by mixing and stirring, and the entire powder for hydrogen storage alloy on which the conductive powder and the cuprous oxide powder are jointly coated is coated with the antioxidant. Therefore, the method for producing a material for a hydrogen storage alloy according to the present invention not only has excellent hydrogen absorption / desorption characteristics immediately after production, but also can retain the characteristics in a powder state for a long period of time. The alloying material can be easily obtained by the dry method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Wada 28-7 Kinao Hinao, Uji-shi, Kyoto Prefecture (72) Inventor Hiroshi Yoshinaga 6-11 Otowa Maede-cho, Yamashina-ku, Kyoto-shi, Kyoto Prefecture (72) Osamu Kajita Kyoto-ken Jin Misaki, 11 Examiner, 11-11 Gogosho, Kitanosho, Uji City (56) Reference JP-A-4-246138 (JP, A) JP-A-3-10002 (JP, A) JP-A-3-12121 (JP, A) ) JP-A-61-132501 (JP, A)

Claims (7)

[Claims] 1. A material for hydrogen storage alloy, characterized in that conductive powder and cuprous oxide powder are bonded and coated on the surface of the powder for hydrogen storage alloy, and the whole is coated with an antioxidant. 2. The conductive powder is copper powder, nickel powder,
The material for hydrogen storage alloy according to claim 1, which is at least one selected from the group consisting of cobalt powder and silver powder. 3. The antioxidant is at least one selected from the group consisting of boron-nitrogen type antioxidants, titanium type antioxidants, aluminum type antioxidants, and silane type antioxidants.
It is above, The material for hydrogen storage alloys of Claim 1 or Claim 2. 4. A powder for hydrogen storage alloy, a conductive powder, a cuprous oxide powder and an antioxidant are put in a high energy type stirrer and the compressive force and shearing energy at the time of mixing and stirring by medium and high speed rotation are utilized. A method for producing a material for a hydrogen storage alloy, characterized in that the surface of the powder for a hydrogen storage alloy is bonded and coated with a conductive powder and a cuprous oxide powder, and the whole is granulated while granulating and the whole is coated with an antioxidant. . 5. The conductive powder is 5 micron particle size to 45 microns, a specific surface area of 2000cm ² / g~7000cm ² / g
5. The method for producing a material for a hydrogen storage alloy according to claim 4, which is the electrolytic copper powder. 6. A powder for hydrogen storage alloy, a conductive powder, a cuprous oxide powder and an antioxidant are put in a high energy type stirrer, and hydrogen is utilized in the initial stage by utilizing the crushing force at the time of mixing and stirring by low speed rotation. The powder for the storage alloy and the conductive powder are pulverized, and in the next step, the conductive powder and the cuprous oxide powder are applied to the surface of the powder for the hydrogen storage alloy by using the compressive force and the shear energy at the time of mixing and stirring by the medium-high speed rotation. A method for producing a material for a hydrogen storage alloy, which comprises jointly coating and granulating while granulating and coating the whole with an antioxidant. 7. A conductive powder is 5 micron particle size to 45 microns, a specific surface area of 2000cm ² / g~7000cm ² / g
7. The method for producing a material for a hydrogen storage alloy according to claim 6, which is the electrolytic copper powder.