JPH10226836A - Hydrogen storage alloy and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hydrogen storage alloy capable of giving a negative pole having high capacity and excellent in cycling characteristics by composing it of a specified combination of Mg, Ni, Nb, Cr, Fe or the like and forming the greater part of amorphous phases in an amorphous structure. SOLUTION: The compsn. of a hydrogen storage alloy is expressed by the general formula of MgMXM'YNZ, and the greater part of amorphous phases is formed in an amorphous structure. In this general formula, M denotes at least one kind of Nb and Ta, M' denotes at least one kind of element selected from Cr, Mo, W, V, Co, Fe, Cu, Pb, Ag, Al, Mn, Zn, Zr, In, Ga, Hf, Si, B, P and rare earth elements, and 0.02<=x<=0.5, 0<=y<=0.2 and 0.8<=z<=1.5 are regulated. Moreover, Mg, Ni, M and M' are uniformly dispersed to form the alloy phases having an amorphous structure. The alloy for a hydrogen storage alloy electrode capable of reversibly executing electrochemical hydrogen occlusion and discharge is obtd.

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 for storing and releasing hydrogen reversibly, and more particularly to a hydrogen storage alloy for a hydrogen storage alloy electrode capable of reversibly storing and releasing electrochemical hydrogen. It relates to the manufacturing method.

[0002]

2. Description of the Related Art In recent years, with the development of portable devices and cordless devices, batteries as power sources have been required to have higher energy density and higher performance. To meet these requirements, nickel-hydrogen storage batteries that have a volume energy density almost equal to that of a lithium ion battery and are resistant to overcharging and overdischarging using a hydrogen storage alloy as a negative electrode have attracted attention. As an alloy used for such a hydrogen storage alloy electrode,
MmNi _5-based multi-component alloy of the mainstream. However, a nickel-hydrogen storage battery having a larger discharge capacity is required as the performance of the device becomes higher. Therefore, an alloy having a larger hydrogen storage capacity is desired as the negative electrode hydrogen storage alloy. Furthermore, in recent years, electric bicycles and the like are required to have excellent output characteristics and light battery weight. As a lightweight alloy having a large hydrogen storage capacity, an Mg ₂ Ni-based alloy (JP-A-6
No. 1-1199045) has a theoretical storage amount of about 1000.
mAh / g, which is considered very promising.

[0003] However, although the Mg ₂ Ni-based alloy has a large hydrogen storage capacity, a plateau (flat portion) exists in a very low pressure region in a pressure composition isotherm diagram (hereinafter referred to as a PCT curve). Therefore, the occluded hydrogen cannot be released near room temperature. For example, hydrogen can be released (discharged) only at a high temperature of 250 ° C. or higher. Therefore, it could not be used as an electrode material. Recently, it has been found that a high capacity (500 mAh / g or more) can be obtained at room temperature by preparing an MgNi-based alloy by a mechanical alloying method such as a ball mill or a planetary ball mill, and further performing a surface treatment. MgN produced by high frequency melting casting or arc melting
An i-based alloy has a crystal structure (cubic system), but an alloy produced by a mechanical alloying method has a powder X
The line diffraction peak has a broad and amorphous structure and has active grain boundaries. As a result, electrochemical activity is greatly improved, and charging and discharging at room temperature becomes possible.

[0004] However, although the initial capacity is high, there is a problem that the discharge capacity is greatly reduced due to charge / discharge cycles, which is not suitable for practical use. Conventionally, in crystalline MgNi-based alloys, rare earth elements, Ca, Cu, Zn, Pb, Sn, I
n, Li, Cd, Al, Ag, Be, V, Cr, Fe,
Attempts have been made to increase the plateau pressure by adding Co, Mn, etc., and to lower the operating temperature even slightly. However, no matter which element is added, it has crystallinity, it is difficult to lower the operating temperature to 150 ° C. or less, and the cycle characteristics are hardly improved (for example, see Japanese Patent Application Laid-Open No. 61-199045). No.). In addition, although a multi-component multi-phase MgNi thin film was examined by physical vapor deposition (PVD), no significant improvement in cycle characteristics was found (for example, US Pat. No. 5,506,069).

[0005]

DISCLOSURE OF THE INVENTION The present invention is to improve an MgNi-based alloy in terms of alloy composition and alloy production,
It is an object of the present invention to provide a hydrogen storage alloy that provides a hydrogen storage alloy electrode having a high capacity and excellent cycle characteristics.

[0006]

According to the present invention, as a result of diligent studies on the effects of various additive elements on the cycle characteristics of an MgNi-based amorphous alloy, an oxide film formed on the surface of an alloy containing Nb or Ta has been found. Mg
Is found to be able to prevent elution into an alkaline electrolyte (usually 31% KOH) and to greatly improve cycle characteristics. The hydrogen storage alloy of the present invention has a general formula MgM _x M ′ _y Ni _z (M is at least one element of Nb and Ta, and M ′ is Cr, Mo, W, V, Co, F
e, Cu, Pb, Ag, Al, Mn, Zn, Zr, I
at least one element selected from the group consisting of n, Ga, Hf, Si, B, P, and a rare earth element; 0.02 ≦
x ≦ 0.5, 0 ≦ y ≦ 0.2, 0.8 ≦ z ≦ 1.5, and most of the alloy phase has an amorphous structure.

[0007]

Hydrogen storage alloy of the embodiment of the present invention is represented by the general formula MgM _x M _'y Ni _z, the majority of the alloy phase, about 75
% Or more has an amorphous structure. The hydrogen storage alloy will be described in more detail below.

The first is an alloy in which Mg, Ni, M and M 'are uniformly dispersed to form an alloy phase having an amorphous structure. The second is an alloy in which Mg, Ni and M form an alloy phase having an amorphous structure, and M ′ is segregated in the alloy. Third, an alloy in which Mg, Ni and M ′ form an alloy phase having an amorphous structure, and M is segregated in the alloy. The fourth is an alloy in which Mg and Ni form an alloy phase having an amorphous structure, and M and M ′ are segregated in the alloy. Fifth, Mg, Ni and M ′ form an alloy phase having an amorphous structure, and M is segregated on the surface of the alloy particles. Sixth, an alloy in which Mg, Ni and M form an alloy phase having an amorphous structure, and M ′ segregates on the surface of the alloy particles.

The hydrogen storage alloy of the present invention can be manufactured by a mechanical alloying method such as a ball mill and a planetary ball mill. The first alloy contains a predetermined amount of Mg, N
It can be manufactured by simultaneously charging i, M, and M ′ and performing mechanical alloying. The second or third alloy is prepared by simultaneously charging a predetermined amount of Mg, Ni and M or M ′ and performing mechanical alloying until an amorphous phase is slightly formed. It can be manufactured by adding and performing mechanical alloying again. For the fourth alloy, a predetermined amount of Mg and Ni are simultaneously charged, and mechanical alloying is performed until an amorphous phase is slightly formed. Then, predetermined amounts of M 'and M are added, and mechanical alloying is performed again. Can be manufactured.

The fifth or sixth alloy comprises a predetermined amount of Mg,
Ni and M 'or M are simultaneously charged and mechanical alloying is performed to produce Mg-Ni-M' or Mg-Ni-M alloy particles having an amorphous structure, and then fine particles of M or M 'are mechanically formed on the alloy surface. It can be manufactured by attaching. The fifth or sixth alloy is prepared by simultaneously charging a predetermined amount of Mg, Ni and M ′ or M, and performing mechanical alloying to produce Mg—Ni—M ′ or Mg—Ni—M alloy particles having an amorphous structure. Then, it can be manufactured by forming an M or M ′ layer on the alloy surface by a plating method.

In the former method for producing the fifth or sixth alloy, the M or M ′ fine particles are made of Mg—Ni
-M 'or Mg-Ni-M alloy can be mechanically attached to a planetary ball mill in an inert gas atmosphere.
It is preferable to use a hybridization method, theta composer or mechanofusion method. Also,
In the former and latter methods for producing the fifth or sixth alloy, Mg-Ni-M 'or Mg-Ni-
After forming the M or M 'layer on the surface of the M alloy, it is preferable to perform a heat treatment in a vacuum at a temperature of 300 ° C or more and 600 ° C or less. This heat treatment further improves the cycle characteristics.

In the mechanical alloying for producing the above first to sixth alloys, the value α obtained by dividing the thickness of the alloy layer adhering to the surface of the ball and the pot by the centrifugal force applied to the ball is 3 × 10 ^The condition of ^-6 sec ² / g or less is preferable for forming an amorphous structure.

[0013]

Embodiments of the present invention will be described below in detail. << Example 1 >> Commercially available Mg (100 mesh or less) 2.4
3g and Ni (less than 100 mesh) 5.87g and Nb
0.93 g (100 mesh or less) was charged into a 500 cc stainless steel ball mill pot, and 40 stainless steel balls having a diameter of about 19 mm (28 g) were charged thereon. After the inside of the pot was replaced with argon, the rotation speed was 60
Perform a ball mill at 10 rpm for 10 days, and then use MgNiNb _0.1
An alloy was made. The sum of the inner wall area of the pot and the surface area of all the balls used here was about 760 cm ² , the volume of the alloy was 2.1 cc, and the thickness of the alloy layer was 2.8 × 10 ⁻³ c.
m. On the other hand, the centrifugal force of the ball is 28 g × 4 because the weight of the ball is about 28 g and the radius of the pot is 4 cm.
cm × (angular velocity 2π / sec) ² from 4.42 × 10 ³ g
· The cm / sec ^2. Therefore, the α value is 0.63 × 10 ^-6
sec ² / g. Thereafter, the alloy in the pot was recovered, and powder X-ray diffraction measurement and production of a pellet electrode were performed.

FIG. 1 shows a powder X-ray diffraction pattern of the obtained alloy. It can be seen that the pattern is broad and has an amorphous structure. Further, when the element distribution on the cross section and the surface of the alloy particles was observed with an electron probe microanalyzer (EPMA), it was confirmed that the respective elements were homogeneously mixed. The pellet electrode was prepared by adding 3 g of Ni powder (particle size: several μm) and 0.12 g of polyethylene powder to 1 g of the above alloy powder and mixing well, and then formed into a cylindrical pellet having a diameter of 25 mm under a pressing pressure of 5 tons. Was used. Using this pellet electrode as the negative electrode, and using a sintered nickel hydroxide positive electrode having several times the capacity of the negative electrode as the positive electrode, an open-cell battery rich in an electrolytic solution consisting of an aqueous solution of potassium hydroxide was produced to improve the electrode characteristics. Examined. FIG. 2 shows charge / discharge cycle characteristics. A in the figure shows the characteristics of the battery using the above-mentioned electrode. B shows the characteristics of a battery using an alloy to which Nb was not added for the negative electrode for comparison. As apparent from FIG. 2, the maximum discharge capacity is 486 mAh by adding Nb.
/ G (first cycle) is slightly improved, indicating that the cycle characteristics are greatly improved. In the alloy production using the above ball mill, if the number of revolutions of the ball is reduced and the α value exceeds 3 × 10 ⁻⁶ sec ² / g, it becomes difficult to form an amorphous phase even when the ball mill time is extended. .

<< Embodiment 2 >> Mg under the same conditions as in Embodiment 1
2.43 g, 5.87 g of Ni, and 1.81 g of Ta (100 mesh or less) were put into a ball mill pot, and ball-milled for 10 days to produce a MgNiTa _0.1 alloy.
Thereafter, a pellet electrode was prepared in the same manner as in Example 1, and the charge / discharge characteristics were measured. Table 1 shows the maximum discharge capacity and the capacity retention rate. The capacity retention rate is (capacity at the 10th cycle) /
(1st cycle capacity) × 100 (%). When Ta is used instead of Nb, the maximum discharge capacity is almost unchanged,
The cycle characteristics were not as good as those of Nb, but were significantly improved as compared with those without the addition.

<< Embodiment 3 >> Mg under the same conditions as in Embodiment 1
2.43 g, Ni 5.87 g, Nb 0.93 g and T
0.905 g of a was charged into a ball mill pot, and ball milled for 10 days to prepare an MgNiNb _0.1 Ta _0.05 alloy. Thereafter, a pellet electrode was prepared in the same manner as in Example 1, and the charge / discharge characteristics were measured. Table 1 shows the maximum discharge capacity and the capacity retention rate. Although the maximum discharge capacity was slightly lower than that in Example 1, the cycle characteristics were slightly improved.

Example 4 In Example 1, the charged amount of Nb was 0.185 g, 0.463 g, 2.78 g, 4.6.
3g, and 6.48g, respectively, alloy MgNiN
b _0.02 , MgNiNb _0.05 , MgNiNb _0.3 , MgN
iNb _0.5 and MgNiNb _0.7 were produced. Table 1 shows the maximum discharge capacity and capacity retention of batteries using these alloys for the negative electrode. Even if the amount of Nb was reduced to about 0.02 atoms, cycle deterioration was suppressed, and even if added to 0.5 atoms, no significant reduction in capacity was observed. But,
When Nb was added up to 0.7 atoms, the capacity reduction became large. Therefore, it is effective that the amount of Nb added is 0.02 or more and 0.5 or less. This range was the same when Ta was added.

Example 5 In Example 1, the amount of Mg and N
The amount of Ni is fixed at 0.6 atom, 0.8 atom, and 1.b.
The ball mill was performed for 10 days under the same conditions while changing the number to 5 atoms and 2.0 atoms. Table 1 shows the maximum discharge capacity and the capacity retention of the battery using the alloy thus produced for the negative electrode. N
When the i amount was 0.6 atoms, the maximum discharge capacity was low, and the cycle characteristics were also reduced. On the other hand, when the amount of Ni was 2.0 atoms, the maximum discharge capacity was significantly reduced. Therefore, the Ni content is desirably from 0.8 to 1.5 atoms.

<< Embodiment 6 >> Mg under the same conditions as in Embodiment 1.
2.43 g and 5.87 g of Ni were ball-milled in advance for 7 days.
93 g, and the ball mill was again operated under an argon atmosphere.
Went for days. An EPMA analysis of the cross section of the completed alloy particles showed that Ng was contained in the MgNi phase having an amorphous structure.
b was observed to be segregated. Table 1 shows the maximum discharge capacity and capacity retention of a battery using the alloy obtained here as a negative electrode.
Shown in Although the maximum discharge capacity was slightly reduced to 470 mAh / g as compared with the case where the elements of Example 1 were uniformly dispersed, the cycle characteristics were improved.

<< Embodiment 7 >> Mg under the same conditions as in Embodiment 1
Ball milling was performed for 10 days using only 2.43 g and 5.87 g of Ni to produce an MgNi amorphous alloy. Next, 5 g of this MgNi amorphous alloy and Ta having a particle size of 0.5 μm were used.
0.5 g of fine particles (equivalent to _{0.05 of} Nb) are charged into a container of Theta Composer (Tokuju Kosakusho THC-70 lab type), and 150 rpm external rotation and 3500 internal rotation in an argon atmosphere.
The surface treatment was performed at rpm for 30 minutes. Thereafter, about half of the recovered alloy was subjected to a heat treatment at 400 ° C. for 2 hours in a vacuum. EPMA analysis of the cross section of the completed alloy particles showed that Nb was segregated only on the surface of the MgNi alloy particles having an amorphous structure. The diffusion of Nb was slightly recognized in the heat-treated alloy as compared to the alloy without the heat treatment.

Table 1 shows the maximum discharge capacity and capacity retention of a battery using this alloy as a negative electrode. The maximum discharge capacity was hardly changed as compared with the uniform dispersion of Example 1, and the cycle characteristics were further improved. In addition, as the surface treatment method,
Methods such as a planetary ball mill, mechanofusion, and hybridization also provided similar effects. The heat treatment temperature is desirably 300 ° C. or more and 600 ° C. or less.
At a temperature exceeding 00 ° C., crystallization of MgNi occurred, resulting in a decrease in discharge capacity.

<< Embodiment 8 >> Mg in the same manner as in Embodiment 7
A Ni amorphous alloy was produced. Next, this MgNi
4 g of an amorphous alloy is used as a 50% aqueous solution of NbCl ₃ 50 c
immersed in c, stirred with a stirrer, Nb plate on the anode,
Using a Ni plate as a cathode, voltage was applied and displacement plating was performed for 30 minutes. It was confirmed from the composition analysis by EPMA that the surface Mg and Nb in MgNi were slightly substituted. Thereafter, about half of the recovered alloy was heat-treated at 500 ° C. for 1 hour in vacuum. The cross section of the completed alloy particles is EPM
A analysis showed that all of the amorphous MgN
Nb segregates only at the surface of i-alloy particles (Nb _0.02 equivalent)
Was observed. Diffusion of Nb was observed in the heat-treated one, as compared with the non-heat-treated one, to the inside of the alloy. Table 1 shows the maximum discharge capacity and capacity retention of a battery using this alloy as a negative electrode. Although the maximum discharge capacity was not changed as compared with that of Example 6, the cycle characteristics were slightly lowered. This seems to be due to the small amount of Nb.

Example 9 Mg under the same conditions as in Example 1
In each of 2.43 g, 5.87 g of Ni, and 0.93 g of Nb, 0.52 g (0.05 atom) and 1.04 g (0.1 atom) of Cr were added.
Atoms), 2.08 g (0.2 atoms), 3.12 g (0.
3 atoms) and mechanical alloying was performed. Table 2 shows the maximum discharge capacity and capacity retention of the batteries using each alloy for the negative electrode. Although the maximum discharge capacity was slightly reduced by the addition of the fourth element, the cycle characteristics were improved. However,
When the addition amount of the fourth element exceeded 0.2 atoms, the maximum discharge capacity was greatly reduced.

<< Embodiment 10 >> M under the same conditions as in Embodiment 1.
g 2.43 g, Ni 5.87 g, and Nb 0.93 g
Was subjected to ball milling for 7 days in advance, and 0.457 g of Zr was added when amorphization was slightly advanced, and ball milling was performed again in an argon atmosphere for 4 days. EPMA analysis of the cross section of the completed alloy particles showed that Zr was segregated in the MgNiNb phase having an amorphous structure. Table 2 shows the maximum discharge capacity and capacity retention of a battery using this alloy as a negative electrode. Although the maximum discharge capacity was slightly reduced, the cycle characteristics were improved.

<< Embodiment 11 >> M under the same conditions as in Embodiment 1.
g 2.43 g, Ni 5.87 g, and V 0.509 g
Was subjected to ball milling for 7 days in advance, and 0.93 g of Nb was added at the time when the amorphization was slightly advanced, and the ball mill was again performed in an argon atmosphere for 4 days. When the cross section of the completed alloy particles was analyzed by EPMA, it was observed that Nb was segregated in the MgNiV phase having an amorphous structure. Table 2 shows the maximum discharge capacity and capacity retention of a battery using this alloy as a negative electrode. Although the maximum discharge capacity was slightly reduced, the cycle characteristics were improved.

Example 12 In Example 7, instead of Cr, Mo, W, Fe, Pb, Ag, Al, Mn, and Z were used.
n, In, Ga, Hf, Si, B, P, or La at 0.
Mechanical alloying was performed by adding an amount equivalent to 05 atoms.
Table 2 shows the maximum discharge capacity and capacity retention of the battery using the obtained alloy as the negative electrode. All of the alloys obtained under these conditions had an amorphous structure and the maximum discharge capacity was slightly reduced, but the cycle characteristics were improved. The effect of the addition amount was almost the same as in the case of Cr.

<< Embodiment 13 >> M under the same conditions as in Embodiment 7.
The g2.43g and Ni5.87g and Nb0.93g ball mill for 10 days to prepare a MgNiNb _0.1 amorphous alloy. Next, 5 g of the MgNiNb _0.1 amorphous alloy and 0.5 g of Co fine particles having a particle size of 0.1 μm.
(Equivalent to _0.14 Co) was mixed in a planetary ball mill (P-5, manufactured by Philitchie) at an acceleration of 6 G for 10 minutes in an argon atmosphere. Thereafter, about half of the recovered alloy was subjected to a heat treatment in vacuum at 600 ° C. for 30 minutes. An EPMA analysis of the cross section of the completed alloy particles showed that Co was segregated only on the surface of the MgNiNb alloy particles having an amorphous structure. Then, the heat-treated one has C
The diffusion of o was observed. Table 2 shows the maximum discharge capacity and capacity retention of a battery using this alloy as a negative electrode. The maximum discharge capacity was almost the same as that of the MgNi amorphous alloy, and the cycle characteristics were improved.

Example 14 An MgNiNb _0.1 amorphous alloy was produced under the same conditions as in Example 11. next,
5 wt% of this MgNiNb _0.1 amorphous alloy 5 g
A Cu layer (corresponding to Cu _0.05 ) was formed on the surface of the alloy particles by immersion in a copper sulfate aqueous solution for 10 minutes and displacement plating. Thereafter, about half of the recovered alloy was subjected to a heat treatment at 450 ° C. for 1 hour in a vacuum. The cross section of the completed alloy particles is EPM
A analysis showed that all of the amorphous MgN
It was observed that Cu was segregated only on the surface of the iNb alloy particles. The diffusion of Cu was slightly recognized in the alloy which had been subjected to the heat treatment as compared with the case where the heat treatment was not performed. Table 2 shows the maximum discharge capacity and capacity retention of a battery using this alloy as a negative electrode. The maximum discharge capacity was almost the same as that of the MgNi amorphous alloy, and the cycle characteristics were improved.

[0029]

[Table 1]

[0030]

[Table 2]

As mechanical alloying, a planetary ball mill other than a ball mill was effective. The planetary ball mill has an advantage that alloying can be performed in a short time because a strong centrifugal force is applied. The heat treatment temperature in a vacuum is preferably a temperature at which MgNi does not recrystallize and a temperature at which the surface metal is thermally diffused, and most preferably 300 ° C. or more and 600 ° C. or less.

[0032]

As described above, according to the present invention, the conventional M
As compared with a gNi binary alloy or a MgNiM 'multi-component alloy, a hydrogen storage alloy which provides a negative electrode having a high capacity and excellent cycle characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing a powder X-ray diffraction pattern of a hydrogen storage alloy in one example of the present invention.

FIG. 2 is a diagram showing charge / discharge cycle characteristics of a battery using a hydrogen storage alloy according to one embodiment of the present invention for a negative electrode.

Claims (13)

[Claims] 1. The general formula MgM _x M ′ _y Ni _z (M is at least one element of Nb and Ta, M ′ is Cr, M
o, W, V, Co, Fe, Cu, Pb, Ag, Al, M
at least one element selected from the group consisting of n, Zn, Zr, In, Ga, Hf, Si, B, P, and a rare earth element; 0.02 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.2 , 0.8 ≦
A hydrogen storage alloy represented by z ≦ 1.5), wherein most of the alloy phase has an amorphous structure. 2. An alloy phase having an amorphous structure in which Mg, Ni, M and M ′ are uniformly dispersed.
The hydrogen storage alloy according to the above. 3. The hydrogen storage alloy according to claim 1, wherein Mg, Ni and M form an alloy phase having an amorphous structure, and M ′ segregates in the alloy. 4. The hydrogen storage alloy according to claim 1, wherein Mg, Ni and M ′ form an alloy phase having an amorphous structure, and M is segregated in the alloy. 5. The hydrogen storage alloy according to claim 1, wherein Mg and Ni form an alloy phase having an amorphous structure, and M and M ′ are segregated in the alloy. 6. The hydrogen storage alloy according to claim 1, wherein Mg, Ni and M ′ form an alloy phase having an amorphous structure, and M segregates on the surface of the alloy particles. 7. The hydrogen storage alloy according to claim 1, wherein Mg, Ni and M form an alloy phase having an amorphous structure, and M ′ segregates on the surface of the alloy particles. 8. The method for producing a hydrogen storage alloy according to claim 2, wherein predetermined amounts of Mg, Ni, M and M ′ are simultaneously charged and mechanically alloyed. 9. Predetermined amounts of Mg, Ni and M or M ′
5. The hydrogenation according to claim 3, wherein the metal alloying is performed at the same time, the mechanical alloying is performed to the extent that an amorphous phase is slightly formed, and then a predetermined amount of M 'or M is added and the mechanical alloying is performed again. Manufacturing method of occlusion alloy. 10. A method in which predetermined amounts of Mg and Ni are simultaneously charged and mechanical alloying is performed until an amorphous phase is slightly formed, and then predetermined amounts of M ′ and M are added and mechanical alloying is performed again. The method for producing a hydrogen storage alloy according to claim 5, characterized in that: 11. A method in which predetermined amounts of Mg, Ni and M ′ or M are simultaneously charged and subjected to mechanical alloying to produce Mg—Ni—M ′ or Mg—Ni—M alloy particles having an amorphous structure. The method for producing a hydrogen storage alloy according to claim 6, wherein M or M 'fine particles are mechanically attached. 12. A predetermined amount of Mg, Ni and M ′ or M are simultaneously charged and subjected to mechanical alloying to produce Mg—Ni—M ′ or Mg—Ni—M alloy particles having an amorphous structure, and then to the alloy surface. The method for producing a hydrogen storage alloy according to claim 6 or 7, wherein the M or M 'layer is formed by a plating method. 13. A hydrogen storage alloy electrode using the hydrogen storage alloy according to claim 1.