JP3369838B2 - Hydrogen storage alloy electrode - 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 electrode used as a negative electrode of a battery, and more particularly to a hydrogen storage alloy electrode having improved performance for initial activation.

[0002]

2. Description of the Related Art A nickel-hydrogen battery using a hydrogen storage alloy as a negative electrode is generally subjected to a chemical conversion treatment in which charging and discharging are repeated a plurality of times after sealing the battery in order to achieve initial activation of the hydrogen absorption alloy. It

The initial activation of this nickel-hydrogen battery is greatly influenced by the catalytic activity and conductivity of the alloy surface.

Therefore, in the manufacturing process of the hydrogen storage alloy electrode, a method of modifying the alloy particles and the surface of the electrode with an alkaline aqueous solution (Japanese Patent Publication No. 4-79474) and a method of subjecting the alloy particles to hydrochloric acid treatment (Japanese Patent Laid-Open No. Hei 5) No. 225975), a method in which the electrode surface is partially covered with nickel and chemically modified (JP-A-62-22370) and the like have been proposed.

According to the method of treating the surface of the alloy with an aqueous alkaline solution or hydrochloric acid, the oxide film formed on the surface of the alloy is removed, and elements such as nickel constituting the alloy are exposed on the surface, resulting in catalytic activity and conductivity. Sex is improved. Further, according to the method of coating the electrode surface with nickel, the nickel on the electrode surface improves catalytic activity and conductivity.

[0006]

However, there is a problem that a sufficient initial activation effect cannot be obtained by any of the methods. An object of the present invention is to provide a hydrogen storage alloy electrode that can obtain a sufficient initial activation effect.

[0007]

Therefore, as a result of intensive studies, the present inventors have found that the conventional nickel alloy that should contribute to the improvement of catalytic activity and conductivity was a crystalline alloy. Found, instead of this crystalline nickel alloy,
The inventors have experimentally clarified that the use of an amorphized nickel alloy is effective in improving catalytic activity and conductivity, and by extension, improving initial activation, and have completed the present invention.

[0008] Hydrogen absorbing alloy electrodes according to the present invention, a powder A of the hydrogen storage alloy, consist of a mixture of a powder B of an amorphous alloy containing nickel, before and particles of the powder A
The particles of the powder B are bonded to each other, and at the bonding interface,
A new one containing the constituent elements of powder A and the constituent elements of powder B
The bonding layer C having a different composition is formed. Specifically, the powder B is mixed in a weight ratio of 0.1% or more and 20% or less with respect to the weight of the entire mixture.

In the hydrogen storage alloy electrode, the surface of the amorphous alloy forming the powder B is disturbed more than the surface of the crystalline nickel alloy, so that the catalytic activity is improved as compared with the crystalline nickel alloy.

Specifically, amorphous alloys are B, C
It contains at least one element selected from a, Nb, P, Ta, Y, Zr, and rare earth elements. This facilitates amorphization of the nickel alloy.

In the present invention, particles of powder A and powder B
The particles are joined by, for example, a sintering method or mechanical alloying. As a result, heat is applied to the bonding surfaces of both particles, and the constituent elements of the powder A and the powder B are applied to the bonding portion.
Due to the diffusion of the component elements of, the bonding layer C having a new composition is formed. The bonding layer C contributes to the improvement of the catalytic activity and firmly bonds the particles of the powder A and the particles of the powder B to further improve the conductivity.

As a method for amorphizing the nickel alloy to be the powder B, a known single-roll quenching method or a hydrogen absorption excitation method in which hydrogenation / dehydrogenation is repeated in the alloy powder can be adopted, but the latter method. According to the method, since amorphization using hydrogen is performed, an amorphous alloy having high reactivity with hydrogen can be obtained, and further catalytic activity and conductivity can be improved.

[0013]

According to the hydrogen storage alloy electrode of the present invention, a higher initial activation effect than before can be obtained.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings. As shown in FIG. 1, the hydrogen storage alloy electrode according to the present invention is formed of a mixture of a hydrogen storage alloy powder A and a nickel-containing amorphous alloy powder B. As a hydrogen storage alloy,
Well-known alloys such as La-Ni based alloys and Zr-Ni based alloys can be used. As the amorphous alloy containing nickel, LaNi ₂ , Ti ₂ Ni, Zr ₂ Ni, Ca ₃ N are used.
i ₂ , NbNi, Ni ₃ Y ₇ , Ni ₃ B ₂ or the like can be used. Powder B is 0.1% by weight based on the total weight of the mixture.
The above is mixed in a weight ratio of 20% by weight or less.

Next, a method of manufacturing the hydrogen storage alloy electrode according to the present invention will be described. Preparation of hydrogen-absorbing alloy powder The predetermined component elements that should constitute the hydrogen-absorbing alloy are mixed in a predetermined molar ratio, respectively, and this is melted by arc melting or high frequency induction melting in an argon atmosphere, and then naturally cooled. A hydrogen storage alloy ingot is produced. Then, the hydrogen storage alloy ingot is pulverized to obtain hydrogen storage alloy powder A having an average particle size of 10 to 150 μm.

Preparation of Amorphous Alloy Powder Preparation by Single Roll Quenching Method Predetermined constituent elements that should constitute a nickel alloy are mixed in predetermined molar ratios, respectively, and then melted by arc melting in an argon atmosphere or high frequency induction melting. Then, natural cooling is performed to produce a nickel alloy ingot. Then, the nickel alloy block is put into a quartz tube (14) as shown in FIG.
This is melted by high frequency induction melting, and the melt is injected from the nozzle hole at the tip of the quartz tube (14) onto the surface of the rotating roll (15). The ribbon-shaped amorphous alloy thus obtained is pulverized to have a particle size of 10 μm or less to produce amorphous alloy powder.

The single roll quenching method is 400 Torr of A
The roll (15) is made of Cu and has a diameter of 20 cm and a rotation speed of 4000 rpm. The nozzle hole at the tip of the quartz tube has an inner diameter of 0.3 mm, and the gap with the roll surface is 1 mm. The pressing force P applied to the molten metal is set to 0.5 to 1.0 kgf / cm ² .

Production by Hydrogen Absorption Excitation Method A nickel alloy ingot is similarly produced by arc melting or high frequency induction melting, and then the nickel alloy ingot is made 150 μm thick.
After crushing to the following particle size and filling the alloy powder in a pressure-resistant SUS container, hydrogenation / dehydrogenation is repeated at room temperature for 200 cycles. Here, the hydrogenation is performed by supplying 10 atm of hydrogen into the container for 5 minutes. The dehydrogenation is performed by evacuating the inside of the container by a rotary pump for 10 minutes. As a result, amorphous alloy powder B having a particle size of 10 μm or less is obtained.

Preparation of Hydrogen Storage Alloy Electrode Method by Simple Mixing Hydrogen storage alloy powder A and amorphous alloy powder B were mixed in predetermined amounts respectively, and then an aqueous solution of a binder was mixed to prepare a paste, The paste is applied to both surfaces of a core body made of punching metal plated with nickel to prepare an alloy electrode.

Method by mechanical alloying Hydrogen-absorbing alloy powder A and amorphous alloy powder B are mixed in predetermined amounts, respectively, and then the mixture is put into a dry water-cooled ball mill and subjected to ball mill treatment (mechanical alloying). Here, the ball mill is made of SUS, its diameter is 2 cm, and the amount of balls is approximately the same as the amount of alloy. The rotation speed of the ball mill is set to 80 rpm, and the treatment is performed for about 10 hours in an argon atmosphere at room temperature. As a result, the particles of the powder A and the particles of the powder B are bonded to each other as shown in FIG. 1, and a bonding layer C having a new composition containing the constituent element of the powder A and the constituent element of the powder B is formed at the bonding interface. Will be done.

Next, the alloy in which the particles are joined as described above is crushed to prepare an alloy powder having an average particle size of 75 μm, and then an aqueous solution of a binder is mixed with the alloy powder to prepare a paste. Then, the paste is applied to both surfaces of a core body made of punching metal plated with nickel to prepare an alloy electrode.

In the preparation of the alloy electrode, a method of mixing the alloy powder with a binder, filling the foamed nickel porous body with the binder, and pressurizing the mixture to form a predetermined electrode shape is also possible. Can be adopted. The test electrode used for the unipolar cell test described later is produced by this method.

[0023]

EXAMPLE FIG. 4 shows the conditions of Experiments 1 to 19 conducted to examine the initial activation performance of the hydrogen storage alloy electrode of the present invention.
FIG. 5 shows the experimental result. Here, base alloy A
Is a hydrogen storage alloy, alloy B is a nickel alloy, and the weight ratio to the weight of the entire mixture of alloy B is set to 5% by weight.

In the experiment, a unipolar test cell having the structure shown in FIG. 3 was prepared. The test cell consists of a polypropylene insulating insulating container (5), a test electrode (2) mainly made of a hydrogen storage alloy, and a cylinder having an electrochemical capacity sufficiently larger than that of the test electrode (2). Shaped sintered nickel electrode
(3) and a plate-shaped sintered nickel reference electrode (4) are arranged. The sintered nickel electrode (3) is the upper surface of the closed container (5).
It is supported at the lower end of the positive electrode lead (7) connected to (6). The test electrode (2) is vertically supported by the lower end of the negative electrode lead (8) connected to the upper surface (6) of the closed container (5) and is housed in the center of the inside of the sintered nickel electrode (3). Has been done.

The positive electrode lead (7) and the negative electrode lead (8) penetrate through the upper surface (6) of the closed container (5) to be exposed to the outside and are connected to the positive electrode terminal (9) and the negative electrode terminal (10), respectively. ing. The test electrode (2) and the sintered nickel electrode (3) are immersed in an alkaline electrolyte (30% by weight potassium hydroxide aqueous solution) injected into the closed container (5). In addition, inside the closed container (5), nitrogen gas is filled in the space above the alkaline electrolyte, and the test electrode (2) has a predetermined pressure (7 atm).
I am putting on. Furthermore, a pressure gauge (11) and a relief valve (12) are provided at the center of the upper surface (6) of the closed container (5) to prevent the internal pressure of the closed container (5) from rising above a predetermined value. The relief pipe (13) is connected.

In the experiment, each test cell was charged at 50 mA / g for 8 hours at room temperature, then rested for 1 hour, and then discharged at 50 mA / g to a discharge rest voltage of 0.9V. After that, the process of resting for 1 hour is set as one cycle, and charging / discharging is repeated.
(mAh / g) was measured.

As shown in FIG. 4, in Experiment Nos. 1 to 6, LaNi _3.2 CoMn _0.6 Al _0.2 was adopted as the base alloy A, whereas LaNi ₂ , Ti as the amorphized alloy B were used.
₂ Ni, and Zr ₂ Ni, or electrodes mixed with Ca ₃ Ni ₂ (Experiment No. 1-4), an electrode obtained by mixing crystalline alloys LaNi ₂ as a comparative example (Run No. 5), consisting of only the base alloy An electrode (Experiment No. 6) was prepared and an experiment was conducted.
As a method for producing an amorphous alloy, a single roll quenching method,
Simple mixing was adopted as the alloy mixing method.

As a result, the results shown in FIG. 5 were obtained. In FIG. 5, the activation degree represents the ratio (%) of the discharge capacity at the first cycle to the maximum capacity, and the initial activation degree can be quantitatively evaluated by this value. As shown, in Experiment Nos. 1 to 4 in which the amorphized nickel alloy was mixed, a high degree of activation was obtained, whereas in Experiment No. 5 in which the crystalline nickel alloy was mixed,
Also, in Experiment No. 6 in which the electrode was produced only from the hydrogen storage alloy, the degree of activation was low.

Experiment Nos. 7 to 15 shown in FIG. 3 are based on the base alloy A.
ZrNi _1.1 Mn _0.7 V _0.2 is adopted as
As amorphized alloy B, LaNi ₂ and Ti _{2 respectively}
Ni, Zr ₂ Ni, NbNi, a material obtained by adding P 20 wt% _{Ni, Ni 3 Y 7, Ni} 3 B 2 were mixed electrodes (Experiment No. 7
13), an electrode (Experiment No. 14) in which a crystalline alloy Zr ₂ Ni was mixed as a comparative example, and an electrode (Experiment No. 15) composed only of the base alloy were prepared and the experiment was conducted.
Similarly, a single-roll quenching method was used as the method for producing the amorphous alloy, and simple mixing was used as the alloy mixing method.

As shown in FIG. 5, in Experiment Nos. 7 to 13 in which the amorphized nickel alloy was mixed, a high degree of activation was obtained, while in Experiment No. 14 in which the crystalline nickel alloy was mixed, In Experiment No. 15 in which the electrode was made only from the hydrogen storage alloy, the degree of activation was low. From these results, it can be seen that when an electrode is prepared by mixing nickel alloy powder with hydrogen storage alloy powder, the initial activation is improved, and when an amorphized alloy is used as the nickel alloy, the initial activation is further improved. Is supported.

Experiment Nos. 16 and 17 shown in FIG. 4 are the alloy combinations of Experiment No. 1 and Experiment No. 9 in which the most excellent effects were obtained in Experiment Nos. 1 to 6 and 7 to 15, respectively. As a method, mechanical alloying is adopted.

In each case, as shown in FIG. 5, a higher degree of activation is obtained than in the case of simple mixing. this is,
By employing mechanical alloying, a bonding layer C having a new composition containing the constituent elements of both powders is formed at the bonding interface between the particles of powder A and the particles of powder B as shown in FIG.
Are considered to have contributed to the improvement of initial activation.

Experiment Nos. 18 and 19 of FIG. 4 are obtained by adopting the hydrogen absorption excitation method as a method of producing an amorphous alloy in the combination of the alloys of Experiment No. 1. Adopt mixed,
Experiment number 19 employs mechanical alloying.

As shown in FIG. 5, in any mixing method, a higher degree of activation is obtained as compared with the case where the amorphization by the single roll quenching method is adopted.

On the other hand, in Experiment Nos. 20 and 21 of FIG. 4, in the combination of the alloys of Experiment No. 9, the hydrogen absorption excitation method was adopted as the method for producing the amorphous alloy. In experiment No. 21, mechanical alloying is adopted. As shown in FIG. 5, in any of the mixing methods, a higher degree of activation is obtained as compared with the case where the amorphization by the single roll quenching method is adopted.

Therefore, from the results of Experiment Nos. 18 to 21,
It can be said that the hydrogen absorption excitation method is excellent as an amorphization method. This superiority is considered to be due to the fact that the hydrogen absorption excitation method is an amorphization method using hydrogen, and thus an amorphous alloy highly reactive with hydrogen can be obtained.

Further, FIG. 6 shows the results of measuring the degree of activation in the combination of alloys of Experiment No. 9 by changing the weight ratio with respect to the weight of the entire mixture of amorphous alloy B in the range of 0 to 40% by weight. ing. As is clear from this result, when the weight ratio of the alloy B exceeds 0.1% by weight, a high degree of activation is obtained, and the degree of activation increases as the mixing ratio further increases. However, when the weight ratio of the alloy B exceeds 30% by weight, the rate of increase in the activation degree is low, and the maximum capacity is sharply decreased. Therefore, it can be said that it is desirable to set the weight ratio with respect to the weight of the entire mixture of the amorphous alloy in the range of 0.1% by weight to 20% by weight.

The above description of the embodiments and examples is for explaining the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope. . The configuration of each part of the present invention is not limited to the above-described embodiments and examples, and it goes without saying that various modifications can be made within the technical scope described in the claims.

[Brief description of drawings]

FIG. 1 is an enlarged view showing the structure of a hydrogen storage alloy electrode according to the present invention.

FIG. 2 is a diagram showing a manufacturing process of an amorphous alloy by a single roll quenching method.

FIG. 3 is a partially cutaway perspective view showing the structure of a unipolar test cell.

FIG. 4 is a chart showing conditions of an experiment conducted to verify the effect of the present invention.

FIG. 5 is a chart showing the experimental results of the above.

FIG. 6 is a chart showing the results of an experiment conducted to optimize the mixing ratio of an amorphous alloy.

[Explanation of symbols]

A Hydrogen storage alloy powder B Amorphous alloy powder C bonding interface

─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Shin Fujitani 2-5-5 Keihan Hondori, Moriguchi-shi, Osaka Sanyo Denki Co., Ltd. (72) Ikuro Yonezu 2-chome Keihanhondori, Moriguchi-shi, Osaka No. 5 within Sanyo Electric Co., Ltd. (72) Inventor Koji Nishio 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (56) Reference JP-A-2-82448 (JP, A) Flat 6-124705 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 4/24-4/26 H01M 4/62

Claims (4)

(57) [Claims] 1. Hydrogen storage alloy powder A and nickel
Consisting of a mixture with an amorphous alloy powder B having,
The particles of the powder A and the particles of the powder B are bonded to each other,
At the bonding interface, the constituent elements of the powder A and the powder B are formed.
Water in which the bonding layer C with a new composition containing a split element is formed
Element storage alloy electrode. 2. Amorphous alloys include B, Ca, Nb, P and T.
The hydrogen storage alloy electrode according to claim 1, containing at least one element selected from a, Y, Zr, and a rare earth element. 3. The powder B is an alloy powder that is hydrogenated / dehydrated.
Amorphization by repeated hydrogen absorption excitation method
Hydrogen storage capacity according to claim 1 or claim 2
Gold electrode. 4. The powder B is added to the weight of the whole mixture.
Mixed in a weight ratio of 0.1% to 20% by weight.
Hydrogen storage according to any one of claims 1 to 3.
Alloy electrode.