JP3322449B2 - Method for producing metal hydride electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a metal hydride electrode, and more particularly to a method for producing a metal hydride electrode having high activity.

[0002]

2. Description of the Related Art In recent years, a metal-hydride alkaline storage battery using a hydrogen storage alloy capable of reversibly storing and releasing hydrogen at room temperature as a negative electrode has become a high-output, high-capacity battery.
Attention has been paid. By the way, in order to further improve the battery characteristics of the metal-hydride alkaline storage battery, it is necessary to increase the activity of the hydrogen storage alloy which is a negative electrode constituent material. Various methods have been proposed for performing a surface modification treatment.

[0003] For example, in Japanese Patent Publication No. 4-79474,
A method of treating a hydrogen storage alloy with an alkaline aqueous solution has been proposed. Japanese Patent Application Laid-Open No. 3-98259 proposes a method of treating a hydrogen storage alloy with heated water of 60 ° C. or higher. According to these treatment methods, a nickel-rich layer is formed on the surface of the hydrogen storage alloy by the alkali treatment or the heating water treatment, and the catalytic function of nickel on the surface is enhanced. You will proceed smoothly. Therefore, the oxygen gas generated from the positive electrode at the time of overcharging is efficiently absorbed by the negative electrode hydrogen storage alloy and does not increase the internal pressure of the battery, so that the charge / discharge cycle characteristics of the battery are improved.

However, when the hydrogen storage alloy is treated with an alkaline aqueous solution or the like, the surface of the alloy becomes relatively nickel-rich, and the oxygen absorbing ability of the hydrogen storage alloy is increased. At the same time, a hydroxide layer is formed on the alloy surface by the treatment. This hydroxide layer lowers the conductivity between the hydrogen storage alloys and lowers its activity. For this reason, the above-mentioned method has a disadvantage that the high-rate discharge characteristics and the low-temperature discharge characteristics at the beginning of the charge / discharge cycle are deteriorated.

Further, Japanese Patent Application Laid-Open No. 3-49154 discloses that
A method has been proposed in which an additive for suppressing oxidation is added when a hydrogen storage alloy ingot is pulverized to produce a hydrogen storage alloy powder. According to this method, the oxidation of the hydrogen storage alloy during the production of the metal hydride electrode can be suppressed, and the deterioration of the alloy characteristics can be prevented. Therefore, a battery having high capacity and excellent cycle characteristics from the beginning of the cycle can be obtained.

[0006] However, this method is intended to suppress the oxidation of the hydrogen storage alloy during the preparation of the hydrogen storage alloy powder, and is not a method of positively improving the characteristics of the hydrogen storage alloy itself. On the other hand, Japanese Patent Laid-Open No.
No. 97 proposes a method in which a hydrogen storage alloy is immersed in an alkaline aqueous solution of a soluble hydride such as sodium borohydride, and the generated hydrogen is stored in the hydrogen storage alloy to be in a charged state. According to this method, the surface of the hydrogen storage alloy is reformed to improve the oxygen absorbing ability,
Since the charging reaction is induced by the reducing agent and the negative electrode (hydrogen storage alloy) is charged, oxidation of the alloy surface is suppressed, the charge / discharge cycle characteristics of the battery are improved, and high-rate charge / discharge characteristics and low-temperature discharge characteristics are achieved. Is said to improve.

[0007] However, even with this method, there was a point that further improvement was required.

[0008]

SUMMARY OF THE INVENTION The inventors of the present invention
The above method of immersing a hydrogen storage alloy in an aqueous alkali solution in which soluble hydrides and the like are dissolved (Japanese Patent Application Laid-Open No. 5-135797, etc.) was further examined, and as a result, the type of reducing agent added to the aqueous alkali solution was changed. By increasing the concentration of the reducing agent added, or reducing the size of the hydrogen storage alloy to be treated, or increasing the immersion time, the activity of the hydrogen storage alloy can be improved sufficiently efficiently. I knew that I couldn't do it.

It is considered that the operation and effect of the above method are based on the following principle. That is, when the hydrogen storage alloy is immersed in an aqueous alkali solution containing a reducing agent such as sodium borohydride, hydrogen generated by the reducing agent is prevented from forming a hydroxide film on the alloy surface. At the same time as this action, hydrogen generated from the reducing agent is stored in the alloy and the alloy is charged, so that the activity of the hydrogen storage alloy is improved. From this, it is considered that if the action of hydrogen generated from the reducing agent on the hydrogen storage alloy is increased, the activity of the hydrogen storage alloy can be more effectively improved. However, as described above, the method of changing the type and concentration of the reducing agent or simply changing the particle size of the alloy did not sufficiently improve the processing effect.

The problem to be solved by the present invention is to devise processing conditions which can further enhance the action (surface reforming, improvement of hydrogen storage efficiency) of a reducing agent-containing alkali solution on a hydrogen storage alloy, and thereby to increase the activity. An object of the present invention is to provide a method for producing a metal hydride electrode having a high degree.

[0011]

Means for Solving the Problems The present inventors have completed the following present invention based on the above-mentioned problems. That is, claim 1
The present invention according to the present invention relates to a method for manufacturing a metal hydride electrode, in which a hydrogen storage alloy ingot is pulverized into a hydrogen storage alloy powder and an electrode is produced using the hydrogen storage alloy powder. A method for producing a metal hydride electrode having a hydrogen storage alloy pulverization reduction step of pulverizing in a contained alkaline solution to form a hydrogen storage alloy powder.

The present invention according to claim 2 is characterized in that the pulverizing and reducing treatment is performed on a hydrogen-absorbing alloy ingot having non-uniform strain of less than 6 × 10 ⁻³ . Further, the present invention according to claim 3 is characterized in that the pulverizing reduction treatment is performed using an alkaline solution containing a reducing agent having a pH of 10 or more.

[0013]

According to the method of the present invention having the above structure, the alloy activating effect can be remarkably enhanced as compared with the conventional method in which the hydrogen storage alloy powder or the metal hydride electrode is simply immersed in an alkaline solution containing a reducing agent. The reason may be as follows. In the method of the present invention, a step of pulverizing the hydrogen storage alloy ingot in a reducing agent-containing alkali solution (hereinafter referred to as an alkali reduction treatment solution or simply a treatment solution) (hereinafter referred to as a hydrogen storage alloy pulverization reduction step or simply a pulverization treatment step) In this step, a step of pulverizing the alloy and a step of treating the alloy with a processing solution are simultaneously performed. In other words, what was conventionally two steps is reduced to one step, but this does not mean simply shortening the steps. That is, the pulverizing operation makes the hydrogen storage alloy ingot finer and increases its surface area, so that the alkali reduction treatment solution easily acts on the alloy. At the same time as this action, the following action is added synergistically.

First, pulverization is an operation of applying mechanical energy to a hydrogen storage alloy ingot to make it into powder, and this operation gives energy to the hydrogen storage alloy from the outside. Therefore, during crushing, the enthalpy inside the alloy is temporarily increased. Therefore, the alloy at the time of pulverization and immediately after pulverization is excited to an energy state much higher than a steady state (so-called activated state).
Then, since the alkali reduction treatment solution is filled around the alloy under such a state, the unoxidized surface (new surface) of the alloy newly formed by the pulverization is immediately exposed to the alkali reduction treatment solution. Will be. In other words, since the alloy immediately after pulverization is in a state of being temporarily excited in an alkaline reducing environment, the alloy is easily affected by the processing solution, and at the same time, absorbs the hydrogen generated from the reducing agent to be in a stable state. Therefore, it is considered that hydrogen is efficiently absorbed.

As described above, in the alloy pulverizing process according to the present invention of pulverizing the hydrogen storage alloy ingot in the alkali reduction treatment solution, the surface area of the hydrogen storage alloy is increased, and the alloy is chemically treated with the alkali reduction treatment solution. The effect of making it more susceptible to the action, and the action of temporarily increasing the internal enthalpy of the hydrogen storage alloy itself and temporarily increasing the alloy activity to make it more susceptible to the chemical action of the alkali reduction treatment solution. Has an effect. For this reason, according to the method of the present invention, the effect of the alkali reduction treatment on the hydrogen storage alloy is significantly increased, and as a result, the activity of the hydrogen storage alloy is greatly improved.

Here, the alloy pulverization reduction process according to the present invention
, The non-uniform distortion is 6 × 10 ^-3Less than hydrogen storage
A more reliable operation and effect can be obtained when using a gold ingot,
4.0 × 10^-3The following hydrogen storage alloy ingots
, More preferable effects can be obtained. So
The reason for this will be described in detail in the embodiment section.
When the concentration increases, the activity of the hydrogen storage alloy increases,
Non-uniform distortion 6 × 10^-3These alloys are excellent in activation
Since no activation treatment with a treatment solution is required,
is there.

Further, it is desirable that the alkali reduction treatment solution used in the alloy pulverization reduction step according to the present invention has a pH of 10 or more. The reason is that a reducing agent such as sodium borohydride decomposes at a pH of 10 or more and generates a large amount of hydrogen. The non-uniform distortion is one of the causes of the phenomenon that the Debye ring becomes broad when the Debye ring is measured by a Laue camera or the like, and is a value defined by the following equation (1).

[0018]

(Equation 1)

[0019]

EXAMPLES Examples of the present invention will be described below, and a metal-hydride storage battery will be manufactured using the electrodes of the examples of the present invention as a negative electrode, and the operation and effect of the present invention will be verified using this battery. Example 1 A metal hydride electrode to which the method of the present invention was applied was manufactured as follows. (Alkali reduction treatment of hydrogen storage alloy) Commercially available Mm (mission metal), Ni, Co (cobalt), Al (aluminum), and Mn (manganese) are used as raw materials, and these have an element ratio of 1: 3.4: 0. 8: 0.2: were weighed so as to be 0.6 ratio, composition using a high frequency melting furnace MmNi _{3. 4}
A hydrogen storage alloy ingot (M ₁ ) represented by Co _0.8 Al _0.2 Mn _0.6 was produced. The non-uniform strain of this alloy is 5.4.
× 10 ^-3 .

The hydrogen storage alloy ingot (M ₁ ) was
In a rotary ball mill (made of alumina, inner volume: 1 liter) containing 2 kg of inch-sized alumina balls, the average particle size is 500 μm with the inside being an inert gas atmosphere.
The dry pulverization was carried out to the following. The end of this ground to the hydrogen storage alloy powder M _2. Then, an appropriate amount sodium borohydride 1% of M ₂ powder, an aqueous solution containing 30% potassium hydroxide (hereinafter, referred to such aqueous treatment solution) were placed and the same ball mill, the alloy Average particle size is 1
Ball mill wet pulverization was performed at room temperature until the particle size became 50 μm or less.

After the ball mill wet pulverization, the pulverized powder removed from the ball mill was washed with ion-exchanged water and dried at 40 ° C. under vacuum to obtain a pulverized reduction-treated hydrogen storage alloy powder. This alloy powder is hereinafter referred to as a pulverized reduction alloy (a ₁ ). The operation conditions of the ball mill were as follows: pot rotation speed: 110 rpm, operation duration: about 4 hours.
The particle size of the alloy powder was determined by a JIS sieve. However, the operating conditions are not strictly defined, and may be set appropriately so that the average particle size of the alloy is 150 μm or less. (Preparation of Hydrogen Storage Alloy Electrode)
_{In 1} ), a polytetrafluoroethylene powder as a binder was added in an amount of 5% by weight based on the weight of the active material and kneaded to prepare a paste. This paste was applied to both sides of a current collector made of a punching metal, and then pressed to produce a hydrogen storage alloy electrode (A ₁ ) according to the present invention. [Example 2] (Pulverization reduction treatment of hydrogen storage alloy) The hydrogen storage alloy ingot (M ₁ ) used in Example 1 was annealed in an inert gas at 1000 ° C for 8 hours, and hydrogen storage after annealing was performed. An alloy ingot (M ₃ ) was produced. The non-uniform strain of the annealed hydrogen storage alloy ingot (M ₃ ) was 2.5 × 10 ⁻³ .

This annealed hydrogen storage alloy ingot (M
Regarding ₃ ), the treatment operation was performed in exactly the same manner as in Example 1 to produce a pulverized and reduced hydrogen storage alloy powder (a ₂ ). This alloy powder is hereinafter referred to as a pulverized reduction alloy (a ₂ ). (Preparation of Hydrogen Storage Alloy Electrode)
Except that ₂ ) was used, exactly the same as in Example 1 above,
A hydrogen storage alloy electrode (A ₂ ) according to the present invention was produced. Comparative Example 1 Example 1 was repeated except that an alloy powder was prepared using a 30% aqueous potassium hydroxide solution as a processing solution.
To produce a comparison electrode B ₁ in the same manner as. Except that Comparative Example 2 treated solution using 1% aqueous sodium borohydride solution as to produce an alloy powder to produce a comparison electrode B ₂ in the same manner as in Example 1. Comparative Example 3 Example 2 was repeated except that an alloy powder was prepared using a 30% aqueous potassium hydroxide solution as a processing solution.
(Using hydrogen-absorbing alloy ingot M ₃ was annealed) and to produce a comparison electrode B ₃ in the same manner. Except that Comparative Example 4 treated solution using 1% aqueous sodium borohydride solution as to produce an alloy powder to produce a comparison electrode B ₄ in the same manner as in Example 2. [Comparative Example 5] A hydrogen storage alloy ingot M ₁ was treated with a treatment solution of potassium hydride 30% and sodium borohydride 1% (25%).
C.) for 2 hours, washed with ion-exchanged water, and dried at 40 ° C. under vacuum to obtain an immersion-treated alloy. Then, the comparative electrode B was prepared in the same manner as in Example 1 using the immersion-treated alloy.
₅ was produced. Comparative Example 6 except for using sodium borohydride 1% treatment solution in the same manner as in Comparative Example 5 was produced compared electrode B _6. Comparative Example 7 except for using a hydrogen-absorbing alloy ingot M ₃ are, in the same manner as in Comparative Example 5 was produced compared electrode B _7. Comparative Example 8 using the hydrogen-absorbing alloy ingot M _3, except for using sodium borohydride 1% aqueous solution as an immersion processing solution, in the same manner as in Comparative Example 5 was produced compared electrode B _8. Used as the Comparative Example 9] hydrogen-absorbing alloy ingot M _1, to prepare a comparative electrode B ₉ in the same manner as in Example 1. As used Comparative Example 10] hydrogen-absorbing alloy ingot M _3,
To produce a comparison electrode B ₁₀ in the same manner as in Example 1.

[Experiment 1] The present invention prepared above was used as a pole.
Metal hydride electrode (A₁), (A _Two)as well as
Reference electrode (B₁)-(B_Ten), And this and public
The sintered nickel positive electrode produced by a known method is
The battery was wound with a separator formed between the batteries to form a battery group.
This battery group was inserted into a well-known cylindrical outer can, and 30% by weight
After injecting potassium hydroxide aqueous solution of
A nickel-hydride battery having a capacity of 1000 mAh was manufactured.
Was. Then, each of these batteries was activated under the following conditions.

[0024]Battery activation conditions After charging at 100 mA for 16 hours, rest for 1 hour. Next
Discharge at 200 mAh until the battery voltage reaches 1.0 V
And then rest for one hour. One cycle of this series of operations
And repeat the same operation three times in a room temperature environment.
U. The twelve types of nicks that have been activated in this way
Kel-Hydride storage battery, corresponding to the negative electrode used
And each battery XA₁, XA_TwoAnd XB₁~ XB _TenWhen
I do.

The high-rate discharge characteristics, low-temperature discharge characteristics, and charge / discharge cycle characteristics of each of the above batteries were examined. The high-rate discharge characteristics and the low-temperature discharge characteristics were compared by comparing the measured characteristic values of the batteries, and the charge-discharge cycle characteristics were determined to indicate that the battery life had expired when the battery capacity reached 500 mAh. Considering this, the respective negative electrode characteristics were evaluated by comparing the number of cycles at this time.
However, each characteristic value was measured under the following conditions.

High Rate Discharge Characteristics In a room temperature environment, the battery was charged at 100 mA for 16 hours,
After a pause, the battery is discharged at 4000 mA until the battery voltage reaches 1.0 V, and the discharge capacity is measured. Low temperature discharge characteristics Charge at 100 mA for 16 hours in a room temperature environment. Thereafter, after a pause of 3 hours in a 0 ° C. environment, the battery is discharged at 1000 mA until the battery voltage becomes 1.0 V, and the discharge capacity is measured.

Charge / discharge cycle characteristics In a room temperature environment, the battery is charged at 1500 mA for 48 minutes, and then paused for 1 hour. Next, the battery is discharged at 1500 mA until the battery voltage becomes 1.0 V, and the battery is paused for 1 hour. This series of operations is defined as one cycle, and this cycle is repeated until the battery capacity reaches 500 mAh. (Measurement Results) Table 1 shows the measurement results of the high-rate discharge characteristics, Table 2 shows the measurement results of the low-temperature discharge characteristics, and Table 3 shows the measurement results of the charge / discharge cycle characteristics.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

As is clear from Tables 1 and ₂ , the high-rate discharge characteristics and the low-temperature discharge characteristics of the batteries XA _{1 to} XA ₂ according to the present invention are all more remarkable than those of the comparative batteries XB _{1 to} XB _10. Was excellent. This will be described in more detail. Sodium borohydride _1%, XA 1 ~XA ₂ (crushing reduction method) using potassium 30% aqueous hydroxide as the processing solution, regarding XB ₅ and XB ₇ (immersion method),
Despite the use of the same processing solution, a clear difference was observed due to the difference in the processing method. That is, the battery XA ₁ ~XA ₂ according to the present invention using the grinding reduction treatment method, high-rate discharge capacity than the comparative example batteries XB _5, XB ₇ using dipping method, the significance high value with low-temperature discharge capacity Indicated. From this,
It was confirmed that when the hydrogen storage alloy ingot was pulverized in a reducing agent-containing alkaline solution, the activity of the hydrogen storage alloy was significantly improved as compared with the method of simply immersing the ingot in the solution.

On the other hand, even when the pulverization method is used, the batteries XA ₁ to XA ₁ to XB _{1 according to} the present invention are used in XB ₁ and XB ₃ using a 30% aqueous solution of potassium hydroxide as the processing solution.
Not only XA ₂ but also XB ₉ which did not perform any processing operation
Or than XB _10, high-rate discharge characteristics, poor even with low-temperature discharge characteristics. Almost same thing 1% of sodium borohydride
The same is true for XB ₂ and XB ₄ using an aqueous solution.
However, in the case of sodium borohydride 1%, since the former had a reducing action, the high-rate discharge characteristics and the low-temperature discharge characteristics were slightly higher than those of XB ₉ or XB _{10 in} which no treatment was performed.

Next, the results in Table 3 will be described. As is clear from Table 3, the charge / discharge cycle life of the battery XA ₁ (non-uniform strain 5.4 × 10 ⁻³ ) according to the present invention is comparable to that of the comparative examples (XB _{1 to} XB ₁ ) using alloys having the same non-uniform strain. ₂ , XB ₅
To XB ₆ and XB ₉ ). On the other hand,
Battery XA _{2 according} to the present invention (non-uniform distortion 2.5 × 10 ⁻³ )
So compared to the XA ₁ and all of the comparative example battery, charge-discharge cycle life was remarkably excellent. From this, the superiority (effect) of the method of the present invention was also confirmed from the aspect of charge / discharge cycle life. Although a large cycle life difference was observed between XA ₁ and XA ₂ , it is considered that this was probably due to the difference in non-uniform strain of the alloy.

[Experiment 2] Hydrogen storage alloy ingots having different alloy non-uniform strains were produced by applying the method of the present invention to hydrogen storage alloy ingots having variously changed alloy non-uniform strains, and this alloy powder was used. Various batteries were prepared in the same manner as in Example 1 except that only the alloy nonuniform strain was different. In addition, as a control, a battery prepared in the same manner as above except that a 1% aqueous solution of sodium borohydride was used as a treatment solution, and a battery produced without performing any solution treatment operation were prepared. Then, high-rate discharge characteristics of these batteries were examined under the same conditions as in Experiment 1.

FIG. 1 shows the experimental results. From FIG. 1, the battery to which the method of the present invention was applied showed a high discharge capacity (900 mAh or more) in a wide range of non-uniform strain. On the other hand, batteries prepared using a 1% aqueous sodium borohydride solution as a processing solution and batteries not subjected to any solution processing operation have inferior high-rate discharge characteristics as compared with batteries to which the method of the present invention is applied. In particular, the difference from the battery to which the method of the present invention was applied increased as the alloy non-uniform strain became smaller.

[0036] Based on the results of FIG. 1, in terms of non-uniform distortion, when assessing the effects of the present inventive method, the present invention method applied battery in less than irregular distortion 6 × 10 ^-3, 1% borohydride It shows a higher discharge capacity than a battery prepared using a sodium aqueous solution. That is, it can be seen that the method of the present invention in which the wet pulverizing and reducing treatment using a reducing agent-containing alkali treatment solution is effective at less than a nonuniform strain of 6 × 10 ⁻³ . Further, comparing the discharge capacity of the battery prepared using a 1% aqueous solution of sodium borohydride and the battery to which the method of the present invention is applied, it can be seen that there is a refraction point at a nonuniform strain of 4 × 10 ⁻³ . In other words, it is understood that the method of the present invention becomes more effective when the nonuniform distortion is 4 × 10 ⁻³ or less.

[Experiment 3] In Experiment 3, the effect of the treatment solution PH on the method of the present invention was examined. The experimental conditions are as follows. That is, sodium borohydride is fixed at 1%,
Various treatment solutions were prepared by changing the amount of potassium hydroxide added from 0% to 30% so that the solution PH became 7-14. Using this processing solution, an alloy ingot having a non-uniform strain of 2.5 × 10 ⁻³ was subjected to wet grinding according to the method of the present invention.
For other items, various batteries were manufactured in the same manner as in Example 1, and high-rate discharge characteristics of these batteries were examined under the same conditions as in Experiment 1.

FIG. 2 shows the experimental results. As is clear from FIG. 2, the high-rate discharge characteristics greatly changed at the boundary of the treatment solution PH10, and the discharge capacity value was remarkably reduced below PH10. This indicates that the method of the present invention preferably adjusts the treatment solution PH to 10 or more. (Other Matters) In the above embodiment, sodium borohydride was used as a reducing agent. However, it goes without saying that the reducing agent is not limited to sodium borohydride.
For example, aluminum hydride, sodium hypophosphite, potassium hypophosphite, formalin and the like can be used. It is further noted that the reducing agent in the method of the present invention may be any reducing substance capable of supplying hydrogen to the hydrogen storage alloy during the pulverizing operation in an alkaline solution, and does not exclude a solid-solid reaction.

In the above embodiment, potassium hydroxide was used as the alkali. However, the present invention is not limited to this, and other alkaline substances can be appropriately selected and used. Further, in the above embodiment, water was used as the solvent of the processing solution, but the present invention is not limited to this. In short, in wet grinding,
Any solvent that does not inhibit the action of the reducing substance and the alkaline substance on the hydrogen storage alloy ingot and does not adversely affect the hydrogen storage alloy itself may be used. Further, the compatibility of the reducing substance and the alkaline substance with the solvent is not an essential requirement. In addition, as an example of another solvent, there is a mixed solution of water and alkalis.

[0040]

As described above, according to the method of the present invention, the activity of the hydrogen storage alloy is remarkably improved. The performance of the negative electrode is remarkably improved as compared with the negative electrode to which the conversion treatment method is applied. Therefore, when using the metal hydride electrode according to the present invention, high-rate discharge characteristics, low-temperature discharge characteristics,
Further, a metal-hydride alkaline storage battery having excellent charge-discharge cycle characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between alloy non-uniform strain and high-rate discharge characteristics in a metal-hydride alkaline storage battery using a metal hydride electrode to which the method of the present invention is applied.

FIG. 2 is a graph showing the relationship between the pH of a processing solution and high-rate discharge characteristics in a metal-hydride alkaline storage battery using a metal hydride electrode to which the method of the present invention is applied.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 4/24-4/62 H01M 10/24-10/30 C22C 19/00 B22F 9/00-9 / 30

Claims (3)

(57) [Claims] 1. A method for manufacturing a metal hydride electrode, wherein a hydrogen storage alloy ingot is pulverized into a hydrogen storage alloy powder, and an electrode is manufactured using the hydrogen storage alloy powder. A method for producing a metal hydride electrode, comprising a hydrogen storage alloy pulverization reduction step of pulverizing in an alkaline solution to form a hydrogen storage alloy powder. 2. The metal hydride electrode according to claim 1, wherein the hydrogen storage alloy ingot having a non-uniform strain of less than 6 × 10 ^-3 is subjected to the hydrogen storage alloy pulverization reduction treatment. Method 3. The method for producing a metal hydride electrode according to claim 1, wherein the pulverizing and reducing treatment of the hydrogen storage alloy is performed using an alkaline solution containing a reducing agent having a pH of 10 or more.