JPH08311596A - Hydrogen storage alloy, surface modifying method for hydrogen storage alloy, battery cathode, and alkali secondary battery - Google Patents

Abstract

PURPOSE: To provide a hydrogen storage alloy improved in machinability as well as in chemical stability, perticularly stability in an aqueous solution. CONSTITUTION: This hydrogen storage alloy contains an alloy represented by general formula Mg2 M1y . In this formula, M1 means the elements other than Mg, elements exothermically reactable with hydrogen, Al and B, and is at least one element selected from the elements exothermically unreactive with hydrogen and (y) is defined by 1<y<=1.5. By this method, the alloy easy of activation and improved in hydrogen occluding property can be obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hydrogen storage alloy, a method for modifying the surface of a hydrogen storage alloy, a negative electrode for a battery, and an alkaline secondary battery.

[0002]

2. Description of the Related Art A hydrogen storage alloy is an alloy capable of stably storing and storing hydrogen (as a normal temperature and normal pressure gas) of tens of thousands times its own volume or more. Therefore, the hydrogen storage alloy is regarded as a promising material that can safely, easily store, store and transport hydrogen as an energy source. Further, application to chemical heat pumps, compressors and the like has been studied by utilizing the difference in characteristics between the hydrogen storage alloys, and some of them have been put into practical use. Furthermore, in recent years, a metal hydride battery using hydrogen stored in the hydrogen storage alloy as an energy source and using the hydrogen storage alloy's high catalytic activity for hydrogen storage / release reactions as an electrode material (For example, nickel-hydrogen secondary battery) is being applied and put to practical use.

As described above, the hydrogen storage alloy is
It has potential for various applications by utilizing its chemical properties, and is considered as one of the important materials in the future industry.

As a metal that occludes hydrogen, a metal element (for example, a platinum group element, a lanthanum group element, an alkaline earth element, etc.) that reacts exothermically with hydrogen, that is, can form a stable compound with hydrogen, is used as a simple substance. There are cases where they are used and cases where these metal elements are alloyed with other metals before use. One advantage of alloying is that the binding force between metal and hydrogen is appropriately weakened so that not only the occlusion reaction but also the desorption (release) reaction can be performed relatively easily. The second advantage is the size of the hydrogen gas pressure (equilibrium pressure; plateau pressure) necessary for the reaction, the size of the equilibrium region (plateau region), the change in equilibrium pressure during the process of occluding hydrogen (flat It is possible to improve the occlusion and release characteristics such as The third advantage is enhanced chemical and physical stability.

By the way, in the composition of the conventional hydrogen storage alloy, the metal element capable of reacting exothermically with the above-mentioned hydrogen is A, and the other metals are B, (1) AB ₅ system (for example, LaN).
i ₅ , CaNi _5, etc.), (2) AB ₂ system (eg MgZn)
₂ , ZrNi ₂ etc.), (3) AB type (eg TiNi, T
iFe), (4) A ₂ B type (for example, Mg ₂ Ni, Ca ₂
Fe, etc.), and (5) others (for example, clusters). Of these, (1) LaNi ₅ , (2)
The Laves phase alloys belonging to (1) or some of the alloys belonging to (3) can be reacted with hydrogen at around room temperature and have relatively high chemical stability, so they have been widely studied as materials for electrodes of secondary batteries described above. .

However, the above-mentioned (2) A ₂ B type hydrogen storage alloy has various problems as follows. The stability with hydrogen is too high and it is difficult to release hydrogen after absorbing hydrogen. If the temperature is not relatively high (about 200 to 300 ° C.), the occlusion / release reaction does not occur or the reaction is extremely slow. Relatively low chemical stability, especially in aqueous solution. In addition, it is generally extremely hard and difficult to process such as crushing. As a result, the A ₂ B-based hydrogen storage alloys have not been widely used for purposes other than storage and transportation, but their potential hydrogen storage capacity is equal to or higher than that of other alloy systems by volume, and by weight. It has excellent characteristics of 2 to several times. Therefore,
If the problems of the A ₂ B type hydrogen storage alloy are solved, it will be possible to apply to the same fields as other alloy systems up to now, and to develop new fields using hydrogen storage alloys. Is also connected.

Although the above-mentioned system (5) has been reported scientifically, there are almost no systems that have reached the stage of practical application or practical application.

On the other hand, Japanese Patent Laid-Open No. 6-76817 discloses that
Composition formula Mg _2-x Ni _1-y A _y B _x , where x is 0.1 to 0.1
1.5, y is 0.1 to 0.5, A is Sn, Sb and B
an element selected from the group consisting of i, B represents an element selected from the group consisting of Li, Na, K and Al, for example Mg _1.5 Al _0.5 Ni _0.7 Sn _0.3 , Mg
Magnesium based hydrogen storage alloys such as _1.8 Al _0.2 Ni _0.8 Sn _0.2 are disclosed. Further, the present invention discloses that the hydrogen storage alloy is used as a negative electrode material of an alkaline battery. However, since the hydrogen storage alloy disclosed in the present invention is basically of the A ₂ B type,
Poor hydrogen absorption / desorption characteristics near room temperature. As a result, it is possible to absorb and desorb hydrogen at standard temperature and pressure by coating the alloy surface with a Ni metal compound or a P metal compound as disclosed in the present invention.

As described above, among various hydrogen storage alloys, A
₂ B type alloy has light weight, a feature that a large capacity, and is generally less expensive to feed manner to be manufactured with the composition around the earth alkali metals and iron group metals. However, at the same time, the hydrogen storage alloy has various problems as described above.

[0010]

SUMMARY OF THE INVENTION The present invention is intended to provide a hydrogen storage alloy having improved chemical stability, particularly stability in an aqueous solution, and mechanical workability.

Another object of the present invention is to provide a hydrogen storage alloy having improved hydrogen storage characteristics, particularly hydrogen storage characteristics at room temperature.

Another object of the present invention is to provide a method for modifying the surface of a hydrogen storage alloy, which is capable of enhancing the surface activity of the hydrogen storage alloy to facilitate hydrogen storage.

Further, the present invention is intended to provide a negative electrode for a battery having good stability against an electrode reaction, and an alkaline secondary battery having improved charge / discharge cycle characteristics.

Furthermore, the present invention clarifies means for evaluating the deterioration rate of a hydrogen storage alloy containing magnesium, shows sufficient reversibility and stability for an electrode reaction based on the means, and is a practically usable negative electrode. , And an alkaline secondary battery.

[0015]

According to the present invention, there is provided a hydrogen storage alloy comprising an alloy represented by the following general formula (I).

Mg ₂ M1 _y (I) However, M1 is at least selected from the elements which can exothermically react with Mg, hydrogen, and elements other than Al and B and which do not exothermically react with hydrogen. One element, y
Is defined as 1 <y ≦ 1.5.

Further, according to the present invention, there is provided a hydrogen storage alloy comprising an alloy represented by the following general formula (II).

Mg _2−x M 2 _x M 1 _y (II) where M 2 is an element capable of reacting exothermically with hydrogen, Al
And at least one element other than Mg selected from B, M1 is at least one element selected from the elements other than Mg and M2 and which does not react exothermically with hydrogen, and x is 0 <x ≦ 1.0. , Y is defined as 1 <y ≦ 2.5.

Further, according to the present invention, the following general formula (III)
There is provided a hydrogen storage alloy comprising an alloy represented by:

M _2−x M 2 _x M 1 _y (III) where M is Be, Ca, Sr, Ba, Y, Ra, L
a, Ce, Pr, Pm, Sm, Eu, Gd, Tb, D
y, Ho, Er, Tm, Tb, Lu, Ti, Zr, H
at least one element selected from f, Pd, and Pt, M
2 is an element capable of reacting exothermically with hydrogen, at least one element other than M selected from Al and B, M1 is an element other than M and M2, and is at least selected from an element which does not react exothermically with hydrogen One element, x and y, is defined as 0.01 <x ≦ 1.0 and 0.5 <y ≦ 1.5, respectively.

Further, according to the present invention, the hydrogen storage alloy is
There is provided a method for modifying the surface of a hydrogen storage alloy, which comprises treating with a -X compound (wherein R represents an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a substitution product thereof, and X represents a halogen element). .

Further, according to the present invention, among the peaks obtained by X-ray diffraction using CuKα as a radiation source, the half-value width Δ of at least one of the peaks of the three strong lines.
There is provided a hydrogen storage alloy, wherein (2θ) is 0.3 ° ≦ Δ (2θ) ≦ 10 °.

Further, according to the present invention, 1 magnesium is used.
In an X-ray diffraction peak with CuKα as a radiation source in an alloy containing 0% or more, the apparent half width Δ (2θ ₁ ) at the peak near 20 ° is 0.3 ° ≦ Δ (2θ ₁ ) ≦ 10 °
Or a apparent half-value width Δ (2θ ₂ ) at a peak near 40 ° is 0.3 ° ≦ Δ (2θ ₂ ) ≦ 10 °. .

Further, according to the present invention, a method of surface-modifying a hydrogen storage alloy, in which the hydrogen storage alloy is mechanically treated under vacuum, an inert gas or an atmosphere of hydrogen, further according to the present invention, a hydrogen storage alloy having a group IVA, V group A, VIA group, VIIA group, VIIIA group, IB group, IIB group, II
Preparing a mixture by mixing at least one element selected from Group IB and Group IVB, an alloy composed of the above element, or an oxide of the above element in equimolar proportions; and vacuuming the mixture, Provided is a method for modifying the surface of a hydrogen storage alloy, which comprises a step of performing a mechanical treatment in an atmosphere of an inert gas or hydrogen.

Further, according to the present invention, there is provided a negative electrode for a battery containing a hydrogen storage alloy represented by the following general formula (I).

Mg ₂ M1 _y (I) However, M1 is at least selected from the elements that can exothermically react with Mg, hydrogen, and elements other than Al and B and that do not exothermically react with hydrogen. One element, y
Is defined as 1 <y ≦ 1.5.

Further, according to the present invention, there is provided an alkaline secondary battery having a negative electrode containing a hydrogen storage alloy represented by the following general formula (I).

Mg ₂ M1 _y (I) However, M1 is at least selected from Mg, an element capable of exothermically reacting with hydrogen, an element other than Al and B, and not exothermically reacting with hydrogen. One element, y
Is defined as 1 <y ≦ 1.5.

Further, according to the present invention, there is provided a negative electrode for a battery containing a hydrogen storage alloy represented by the following general formula (II).

Mg _2-x M2 _x M1 _y (II) where M2 is an element that can react exothermically with hydrogen, Al
And at least one element other than Mg selected from B, M1 is at least one element selected from the elements other than Mg and M2 and which does not react exothermically with hydrogen, and x is 0 <x ≦ 1.0. , Y is defined as 1 <y ≦ 2.5.

Further, according to the present invention, there is provided an alkaline secondary battery provided with a negative electrode containing a hydrogen storage alloy represented by the following general formula (II).

Mg _2−x M 2 _x M 1 _y (II) where M 2 is an element capable of reacting exothermically with hydrogen, Al
And at least one element other than Mg selected from B, M1 is at least one element selected from the elements other than Mg and M2 and which does not react exothermically with hydrogen, and x is 0 <x ≦ 1.0. , Y is defined as 1 <y ≦ 2.5.

Further, according to the present invention, among the peaks obtained by X-ray diffraction using CuKα as a radiation source, at least one of the peaks of the three strong lines has a half-value width Δ.
There is provided a negative electrode for a battery including a hydrogen storage alloy having (2θ) of 0.3 ° ≦ Δ (2θ) ≦ 10 °.

Further, according to the present invention, among the peaks obtained by X-ray diffraction using CuKα as a radiation source, the half width Δ of at least one of the peaks of the three strong lines.
Provided is an alkaline secondary battery including a negative electrode containing a hydrogen storage alloy having (2θ) of 0.3 ° ≦ Δ (2θ) ≦ 10 °.

Further, according to the present invention, there is provided a negative electrode containing a hydrogen storage alloy containing magnesium, which is (a) when immersed in an aqueous solution of alkali hydroxide having a normality of 6 to 8: Either the elution rate of magnesium ions is 0.5 mg / kg alloy / hr or less, or the elution rate of magnesium ions into an aqueous alkali hydroxide solution at 60 ° C. is 4 mg / kg alloy / hr or less, and
(b) The elution rate of alloying elements into the alkali hydroxide aqueous solution at room temperature is 1.5 mg / kg alloy / hr or less, or 60 ° C.
There is provided a negative electrode for a battery, wherein the elution rate of the alloy component element in the aqueous alkali hydroxide solution is 20 mg / kg alloy / hr or less.

Further, according to the present invention, a negative electrode containing a hydrogen storage alloy containing magnesium contained in a container,
An alkaline secondary battery comprising a positive electrode housed in the container and arranged with the separator sandwiched in the negative electrode, and an alkaline electrolyte contained in the container, wherein the alkaline electrolyte is contained in the container. An alkaline secondary battery is provided in which the magnesium ion concentration in the alkaline electrolyte is 30 mg / liter or less after 30 days or more have been injected and the container is sealed. .

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The hydrogen storage alloy according to the present invention is characterized by containing an alloy represented by the following general formula (I).

Mg ₂ M1 _y (I) However, M1 is at least selected from the elements which can exothermically react with Mg, hydrogen, and elements other than Al and B and which do not exothermically react with hydrogen. One element, y
Is defined as 1 <y ≦ 1.5.

The above M excluding Mg, an element which does not react exothermically with hydrogen and which can react exothermically with hydrogen, Al and B
As one element, for example, iron, nickel, cobalt, A
Examples thereof include g, Cd, Mn, In, Se, Sn, Ge and Pb. Such M1 can be used in one form or two or more forms. In particular, M1 is an element having a higher electronegativity than Mg, that is, iron, nickel, cobalt, Ag, Cd, Mn, In, Se, S.
It is preferable to use n, Ge, or Pb. Among them, the hydrogen storage alloy in which iron group elements such as iron, nickel, and cobalt are alloyed is chemically stable and can absorb and store hydrogen.
The release reaction is improved. When the iron group element as M1 is used, it has a higher electronegativity than Mg as an element for substituting a part of the iron group element, and is mixed with pure magnesium in an atomic ratio of 10% or less. Element having a property that the volume of the crystal lattice of Mg _1-W M1 _W phase (W is 0 <W ≦ 0.1) in the alloy is smaller than the volume of the crystal lattice of pure magnesium, for example, Mn, Ag, Cd,
An alloy using at least one element of In is preferable.

Table 1 shows the crystal lattice sizes of the alloy of the above element and magnesium and pure magnesium.
The values shown in Table 1 were calculated based on the lattice constants obtained from the diffraction pattern of the prepared alloys by the powder X-ray diffraction method, assuming that the crystal structures of these alloys are hexagonal crystal structures similar to pure magnesium. It was done.

If the W value exceeds 0.1 in the Mg _1-W M1 _W phase, the crystal structure of the alloy phase Mg _{1- W} M1 _W may be different from the hexagonal structure, and the element M1 There is a possibility that the change in the magnesium lattice size due to addition cannot be evaluated correctly. Therefore, the range of W as an index is set to 0 <W ≦ 0.1, but if it is known that the hexagonal crystal is maintained even if W exceeds 0.1, W larger than 0.1 The element M1 may be selected within the range of the value of.

[0043]

[Table 1]

In the above general formula (I), the reason that y of M1 is defined to exceed 1 and be 1.5 or less is as follows.
Description will be made based on the relationship with the hydrogen storage amount, and b) the relationship between chemical stability and mechanical workability.

A) Relation with hydrogen storage amount When the ratio of Mg having a hydrogen storage capacity to M1 (having a property of making a hydride difficult) is 2: y, stoichiometrically y = 1 ( It should be Mg ₂ M1). However, practically, when y is 1 or less, there is a problem in chemical stability and mechanical workability that the present invention intends to solve as described later. In addition, when y is excessively large, some problems occur and the characteristics are not preferable in practical use. For example, when y is larger than 2, microscopically Mg
_It cannot exist only with crystals based on ₂ M1 type and becomes MgM1 ₂ type, that is, Laves phase. This M
GM1 ₂ type alloys having a hydrogen storage capacity. However, the hydrogen storage capacity of MgM1 ₂ type alloys is only 40% to 70% approximately by weight of Mg ₂ M1 type alloy, when it is excessively large y is disadvantageous in terms of capacity density.

B) Relationship between the ratio of the components Mg and M1 and the chemical stability and mechanical workability. Mg ₂ M1 type hydrogen storage alloys generally have Mg: M1 =
The compositional fluctuations, which are generated only at one point of 2: 1, and in which a Mg or M1 deficiency or excess may exist locally while maintaining the Mg ₂ M 1 type structure, are hardly allowed. This will be described based on the state diagram. FIG. 1 shows a state diagram of Mg ₂ Ni (Mg—Ni system) as a typical example of Mg ₂ M 1.
FIG. 2 shows a state diagram of AB ₅ type LaNi ₅ (La—Ni system). These state diagrams are based on "Binary Allo
y Phase Diagrams ", ASM Int
international (USA), 1990. From these FIGS. 1 and 2, Mg ₂ Ni is Mg-Ni.
Only one vertical line is shown on the system phase diagram. On the other hand, LaNi ₅ is shown as a range having a slight bulge on the La—Ni system phase diagram. This is in part whereas to produce an alloy that is regarded as essentially LaNi ₅ same phase also shifted slightly LaNi ₅ in the melt composition as a matter during alloy production, Mg ₂ Ni molten metal tissue in the The deviation is due to the fact that Mg ₂ Ni and the excess component are precipitated in the two-phase eutectoid state. That is, when y is expressed as Mg: Ni = 2: y with y as an arbitrary positive number, if y <1, Mg ₂ Ni and excess Mg are eutectic precipitated. on the other hand,
If y> 1, a eutectic of Mg ₂ Ni and MgNi ₂ or a eutectic of Mg ₂ Ni or MgNi ₂ and Ni occurs.

Mg has lower chemical stability such as corrosion resistance and oxidation resistance than Ni, and has a larger viscosity and malleability than Ni. Also,
When Mg ₂ Ni and MgNi ₂ are compared with each other, Mg ₂ Ni has a structure with higher polarization (ionic bondability) particularly in a hydrogen storage state, and is therefore easily attacked by moisture, oxygen and the like. Therefore, alloys with y <1 have poor chemical stability and can withstand mechanical stress due to the presence of highly viscous Mg at the grain boundaries, but have poor workability. On the other hand, y>
In the case of 1, not only Mg does not coexist but also Mg ₂ Ni
The structure is such that the surface is surrounded by MgNi ₂ or Ni. Therefore, the chemical stability is improved. Further, in the case of y> 1, Ni has high rigidity but has low viscosity.
Brittle fracture occurs in the excess grain boundary phase. Therefore, mechanical processing becomes easy.

As described above, the ratio of the Mg and M1 components is 2:
When expressed as y, the condition for realizing improvement in mechanical workability is y> 1. On the other hand, the capacitive view of maintaining sufficient capacity without relying on MgM1 _2-phase, the upper limit value of the y should be 1.5. Furthermore, y is preferably 1 <y ≦ 1.5 even when only chemical stability is taken into consideration.

When the ratio of Mg and M1 components is expressed as 2: y, the lower limit value of y may be a value slightly larger than 1 in principle, but in reality, it is in the alloy. There are composition fluctuations and segregation. Therefore, the condition for y exceeding 1 in substantially all parts in the alloy depends on the homogeneity of the alloy. Specifically, (a) an alloy is produced by pouring a molten metal of the component elements prepared by using a furnace such as an induction furnace or an arc furnace in the same manner as a normal metal ingot into a container such as a mold, a so-called slow cooling method. In this case, y is preferably 1.05 or more. (b) When the molten metal of the component element is brought into contact with a low temperature and high heat capacity substance such as a rotating roll or a liquid, or when the molten metal is rapidly cooled to produce it, y is It is preferably 1.02 or more. (c) After mixing a plurality of kinds of pure metals or master alloys so as to have the same alloy composition in advance, hot rolling,
Hot press or mechanical mixing (mechanical alloy method)
In the case of manufacturing without a melting step, etc., y is preferably 1.02 or more.

The production method (a) is difficult to enhance the homogeneity as compared with the other methods because segregation during gradual cooling is likely to occur, but the method is simple and most widely adopted. In the manufacturing method of (c), the homogeneity of the alloy is easily influenced by the manufacturing conditions,
It may be necessary to further increase the lower limit of y depending on the conditions. The method (b) has relatively high homogeneity. In addition, when the homogenization of the composition / structure is improved by optimizing the manufacturing conditions or annealing after the manufacturing, y of 1.01 or more can sufficiently achieve the object of the present invention. Various surface analysis methods (EDX, EPMA, etc.) applying an electron microscope and X-ray diffraction measurement methods are adopted for the determination of homogenization. For example, in the surface analysis method, it is determined that the composition distribution of the texture cross section in the alloy is homogeneous when 90% or more of the area ratio of the cross section is the same layer. Further, in the X-ray diffraction measurement method, the ratio of the intensity of the diffraction peak attributed to the Mg or M1 mother alloy or the elemental element contained in this mother alloy to the peak intensity in the case of being present alone is expressed as a percentage. , Homogenization is judged on the basis that the total is 5% or less. From these results, it is expected that the lower limit value of y will fall within the range of about 1.01 to 1.10.

The hydrogen storage alloy according to the present invention allows addition of VB group or VIB group elements to the alloy represented by the general formula (I) at a ratio of 20 atomic% or less.

The hydrogen storage alloy according to the present invention described above has the general formula (I): Mg ₂ M1 _y (where M1 is M
g, an element that can react exothermically with hydrogen, at least one element other than Al and B that does not react exothermically with hydrogen, and y is defined as 1 <y ≦ 1.5. It ) Including alloys represented by. That is,
The hydrogen storage alloy of the general formula (I) may be M such as Ni.
Since y of 1 has a characteristic that y exceeds 1 and is 1.5 or less, chemical stability and mechanical workability are high, and M
It has a high hydrogen storage capacity inherent to A ₂ B type alloys such as g ₂ Ni.

Therefore, even if the hydrogen storage alloy according to the present invention is placed in hydrogen gas containing a slight amount of oxidizing gas such as oxygen or water vapor and reacted therewith, a good hydrogen storage performance is maintained. In addition, it is possible to expand the voluntary use of the alloy, in which the hydrogen storage performance is unlikely to deteriorate even when contacted with an aqueous solution or the like.

Further, when it is necessary to process the alloy into a size and shape suitable for use in advance, the hydrogen storage alloy of the present invention having high workability is advantageous.

Further, the hydrogen storage alloy is gradually made finer with the expansion and contraction of the crystal lattice due to the storage and release of hydrogen, which changes the physical properties (for example, bulk density, contact resistance, conductivity, etc.). When such a change causes a problem, a method is used in which the alloy is pulverized in advance and then used. The hydrogen storage alloy according to the present invention is a conventional Mg ₂ N alloy.
The workability is better than that of the A ₂ B type alloy such as i, and the crushing process can be easily performed, so that the above problems can be satisfactorily dealt with.

As described above, the hydrogen storage alloy containing the alloy represented by the general formula (I) according to the present invention can easily and surely perform the pre-processing before use and the condition control during use. It can be used very effectively as a battery electrode material and the like.

Another hydrogen storage alloy according to the present invention is characterized by containing an alloy represented by the following general formula (II).

Mg _2-x M2 _x M1 _y (II) However, M2 is an element capable of reacting exothermically with hydrogen, Al
And at least one element other than Mg selected from B, M1 is at least one element selected from the elements other than Mg and M2 and which does not react exothermically with hydrogen, and x is 0 <x ≦ 1.0. , Y is defined as 1 <y ≦ 2.5.

For M1, the same element as described for the alloy of the general formula (I) is used.

Examples of the element which can exothermically react with hydrogen other than Mg in M2, that is, the element which can spontaneously form a hydride, are alkaline earth elements such as Be, Ca, Sr and Ba; Y, Ra, La, Ce, Pr, P
m, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
rare earth elements including yttrium such as m, Tb, and Lu; IVa group elements such as Ti, Zr, and Hf; Pd and Pt
Group VIIIa elements such as M2
Can be used in the form of one kind or two or more kinds.
Further, M2 is an element capable of reacting exothermically with hydrogen, A
Mg, which is an element other than Mg selected from 1 and B,
Elements with higher electronegativity, namely B, Be, Y,
Pd, Ti, Zr, Hf, Th, V, Nb, Ta, P
It is preferably at least one element selected from a and Al. By selecting an element having a higher electronegativity than Mg as M2, the difference in electronegativity from hydrogen becomes small, hydrogen in the lattice becomes unstable, and the storage characteristics can be improved. . In particular, Be, which is an alkaline earth metal, can form a chemically stable alloy when alloyed with Mg. In addition, T which is a group IVa element
i, Zr, and Hf easily react with hydrogen and easily form a hydride.

Further, M2 is an element which can exothermically react with hydrogen, is an element other than Mg selected from Al and B, and is prepared by mixing pure magnesium in an atomic ratio of 10% or less. In which the volume of the crystal lattice of the Mg _1-W M1 _W phase (W is 0 <W ≦ 0.1) is smaller than the volume of the crystal lattice of pure magnesium, that is, Li,
It is preferably at least one element selected from Al.

The reason for defining x in the general formula (II) is as follows. When x exceeds 1.0,
The hydrogen storage properties (hydrogen storage amount, flatness of the plateau region, reversibility of adsorption and desorption) possessed by Mg ₂ M1 _y are greatly impaired, and in some cases the crystal structure itself cannot be maintained.
In particular, x is more preferably defined as 0.05 ≦ x ≦ 0.5.

The reason why y in the general formula (II) is defined is as follows. The benefit of y exceeding 1 is for the same reason as explained for the alloy of the general formula (I). When y exceeds 2.5, not only the amount of hydrogen that can be absorbed by the alloy decreases but it becomes difficult to maintain the original structure of the alloy. In particular, y is 1.01 ≦ y
≦ 1.5, more preferably 1.02 ≦ y ≦ 1.5, and further preferably 1.05 ≦ y ≦ 1.5.

Another hydrogen storage alloy according to the present invention is the alloy represented by the above-mentioned general formula (II) with a V content of 20 atomic% or less.
Allowing the addition of Group B or VIB elements.

Another hydrogen storage alloy according to the present invention described above is represented by the general formula (II); Mg _2-x M2 _x M1 _y (however,
M2 is an element capable of reacting exothermically with hydrogen, Al and B
At least one element other than Mg selected from, M1 is at least one element selected from the elements other than Mg and M2 that does not react exothermically with hydrogen, x is 0 <x ≦ 1.0, y Is defined as 1 <y ≦ 2.5. ) Including alloys represented by. That is, the general formula
The hydrogen storage alloy including the alloy of (II) has a part of Mg replaced by an element such as Al shown as M2, and therefore has a storage characteristic, particularly a storage temperature, higher than that of the conventional A ₂ B type hydrogen storage alloy. Of the hydrogen storage alloy becomes remarkable, and the original hydrogen storage capacity of the A ₂ B type hydrogen storage alloy is high. Further, compared with the conventional rare earth-based hydrogen storage alloy, the hydrogen storage amount per weight is large, and it is inexpensive and lightweight. At the same time, in hydrogen storage alloys including the alloy of the general formula (II), y of M1 such as Ni is 1
And has a characteristic of being 2.5 or less, it has excellent chemical stability and mechanical workability. As a result, even if the hydrogen storage alloy is placed in hydrogen gas containing a slight amount of oxidizing gas such as oxygen or water vapor and reacted therewith, a good hydrogen storage performance is maintained. In addition, it is possible to expand the voluntary use of the alloy, in which the hydrogen storage performance is unlikely to deteriorate even when contacted with an aqueous solution or the like.

As described above, in the hydrogen storage alloy containing the alloy represented by the general formula (II) according to the present invention, the storage temperature is remarkably lowered, and the high hydrogen storage capacity of the A ₂ B type hydrogen storage alloy is high. Since it has a function and at the same time can easily and surely perform pre-processing before use and condition management during use, it can be extremely effectively used as an electrode material of a secondary battery.

Still another hydrogen storage alloy according to the present invention includes an alloy represented by the following general formula (III).

M _2-x M2 _x M1 _y (III) where M is Be, Ca, Sr, Ba, Y, Ra, L
a, Ce, Pr, Pm, Sm, Eu, Gd, Tb, D
y, Ho, Er, Tm, Tb, Lu, Ti, Zr, H
at least one element selected from f, Pd, and Pt, M
2 is an element capable of reacting exothermically with hydrogen, at least one element other than M selected from Al and B, M1 is an element other than M and M2, and is at least selected from an element which does not react exothermically with hydrogen One element, x and y, is defined as 0.01 <x ≦ 1.0 and 0.5 <y ≦ 1.5, respectively.

The M1 is the same element as described in the hydrogen storage alloy including the alloy represented by the general formula (I).

The M2 is the same element as described in the hydrogen storage alloy including the alloy represented by the general formula (II).

In the combination of M, M1 and M2,
A ternary alloy in which M is Zr, M1 is Fe, and M2 is Cr, M
Is preferably Zr, M1 is Ni and Co, and M2 is V. A combination of quaternary alloys is preferable.

The reason for defining the y value of M1 and the x value of M2 in the general formula (III) will be described below.

If the value of y is less than 0.5, M, M1,
Since the individual phases of M2 are precipitated respectively, the characteristics as a hydrogen storage alloy are not exhibited and they become chemically unstable. It is preferable that y is a lower limit value that exceeds 1.0 (for example, 1.01). On the other hand, when y exceeds 2.0, not only the amount of hydrogen that can be stored in the alloy decreases, but also it becomes difficult to maintain the original structure of the alloy. The upper limit of y is 1.
It is preferably 5.

When the value of x is less than 0.01, it becomes impossible to obtain a hydrogen storage alloy having good hydrogen storage characteristics at low temperature. When the value of x exceeds 1.0, the crystal structure changes and the original characteristics of the A ₂ B alloy are lost. The more preferable value of x is 0.05 to 0.5.

[0075] Another of the hydrogen storage alloy according to the present invention described above, the general formula _{(III); M 2-x} M2 x M1 y ( provided that
M is Be, Ca, Sr, Ba, Y, Ra, La, C
e, Pr, Pm, Sm, Eu, Gd, Tb, Dy, H
o, Er, Tm, Tb, Lu, Ti, Zr, Hf, P
d, at least one element selected from Pt, M2 is an element capable of reacting exothermically with hydrogen, at least one element other than M selected from Al and B, M1 is M and M2
Other than at least one element selected from the elements that do not react exothermically with hydrogen, x and y are defined as 0.01 <x ≦ 1.0 and 0.5 <y ≦ 1.5, respectively. It ) Including alloys represented by. That is, in the hydrogen storage alloy containing the alloy of the general formula (III), a part of M such as Zr is replaced with the element shown as M2 such as Al, so that the conventional A ₂ B type hydrogen storage alloy is used. The storage characteristics, especially the lowering of the storage temperature, become more remarkable than the alloy, and A ₂ B
-Type hydrogen storage alloy It has the original high hydrogen storage capacity. Also,
Compared with conventional rare earth-based hydrogen storage alloys, the hydrogen storage amount per weight is large, and it is cheap and lightweight.

Therefore, the general formula (III) according to the present invention is
The hydrogen storage alloy containing the alloy represented by is markedly lowered in the storage temperature and has the high hydrogen storage capacity of the A ₂ B type hydrogen storage alloy, and is therefore extremely effective as an electrode material for secondary batteries. Can be used for.

In the surface modification method of a hydrogen storage alloy according to the present invention, the hydrogen storage alloy is treated with an R-X compound (wherein R is alkyl, alkenyl, alkynyl, aryl or a substitution product thereof, and X is a halogen element). To do.

Examples of the hydrogen storage alloy include (1) AB ₅ series (for example, LaNi ₅ series, CaNi ₅ series, etc.) and (2) AB ₂ series (for example, MgZn ₂ series, ZrNi ₂ series) described above.
System), (3) AB system (for example, TiNi system, TiFe system, etc.), (4) A ₂ B system (for example, Mg ₂ Ni system, Ca ₂ Fe system)
System, etc.) can be used.

The hydrogen storage alloy contains an alloy represented by the following general formula (IV).

Mg _2-x M2 _x M1 _y (IV) where M2 is an element capable of reacting exothermically with hydrogen, Al
And at least one element other than Mg selected from B, M1 is at least one element selected from the elements other than Mg and M2 and does not react exothermically with hydrogen, and x and y are each 0 ≦ x ≦ 1.0, 0.5 <
It is defined as y ≦ 2.5.

For M1, the same element as described for the alloy of the general formula (I) is used. For M2, the same element as described for the alloy of the general formula (II) is used.

Particularly, the AB ₅ type and A ₂ B type hydrogen storage alloys, or the hydrogen storage alloys containing the alloy represented by the above general formula (IV) are preferable.

In the R—X compound, R is alkyl, alkenyl, alkynyl, aryl or a substitution product thereof, X is a halogen element, and it has a high reactivity in the order of iodide>bromide> chloride. Such R-X
Examples of the compound include methyl iodide, ethyl bromide,
1,2-dibromoethane, 1,2-diiodoethane and the like can be mentioned.

The RX compound (halide) is preferably reacted with the hydrogen storage alloy in the presence of a solvent for surface modification.

Examples of the solvent include diethyl ether, tetrahydrofuran (THF), di-n-propyl ether, di-n-butyl ether, di-isopropyl ether, diethylene glycol dimethyl ether (diglyme), dioxane and dimethoxyethane (DME). Can be used. These solvents may be used alone or in the form of a mixture. Especially, diethyl ether, TH
F is desirable. When the R—X compound is an alkyl halide, an alkenyl halide, or an aryl halide, it is preferable to use an ether solvent as the solvent. When the R-X compound is an alkenyl compound or an aryl compound, TH having a stronger coordinating force is used.
It is preferable to use F as a solvent. Further, the R-
Among the X compounds, bromide and iodide are easy to react in ether. Among the R-X compounds, a chloride having a low reactivity or a bromide having a substituent can be reacted in THF.

Regarding the concentration of the solution of the RX compound dissolved in the solvent, it is necessary to consider the following 1) to 3) and select suitable conditions.

1) Reactivity of halides (low reactivity is added at high concentration).

2) Ease of side reactions (allyl chloride and benzyl chloride are used in a low concentration because the coupling reaction is likely to occur).

3) Solubility stability of the product (if the solubility is low, the concentration is low. If the concentration is higher than the saturation concentration, solids often precipitate after cooling, and in this case, disproportionation is involved. There is).

The solvent in which the RX compound is dissolved,
It is effective to add a catalyst to accelerate the reaction. Examples of this catalyst include pentalene, indene,
Naphthalene, azulene, heptalen, biphenylene, indacene, acenaphthylene, fluorene, phenalene,
Phenanthrene, anthracene, fluoranthene, acephenanthrylene, anthrylene, triphenylene, pyrene, chrysene, naphthacene, pleiaden, picene,
Perylene, pentaphene, pentacene, tetraphenylene, hexaphene, hexacene, rubicene, coronene,
Fused polycyclic hydrocarbons such as trinaphthylene, heptaphene, heptacene, pinanthrene, ovalen are used. In particular, anthracene is preferable. When a hydrogen storage alloy containing magnesium is treated with a THF solution of an R-X compound to which anthracene is added, a mixture of anthracene and magnesium is in equilibrium between magnesium and anthracene. Therefore, only by adding anthracene as a catalyst to the reaction system of the formula (3) described later, the reaction to the right is promoted, and a better surface modification can be achieved.

In the surface modification method according to the present invention,
It is a particularly industrially effective method to add R-MX (M; one component of a hydrogen storage alloy) synthesized in advance at the initial stage of the reaction to dehydrate and activate the system.

According to the surface modification of the hydrogen storage alloy according to the present invention described above, the storage characteristics, especially the activity can be improved as compared with the unmodified hydrogen storage alloy.

That is, one of the methods for improving the storage characteristics of the hydrogen storage alloy is surface modification of the hydrogen storage alloy. The activity of the hydrogen storage alloy during hydrogen storage occurs by a mechanism called surface segregation, and it is considered that the activity of the hydrogen storage alloy is related to the ease of formation of the catalyst layer on the surface and the performance of the catalyst. When the hydrogen storage alloy is treated with the RX compound, a part M of the constituent elements of the hydrogen storage alloy causes the following reaction.

M + R−X → R-MX (1) or M + αR−X → αR + MX _α (2) When the surface treatment by such a reaction is performed, mild segregation occurs on the surface of the hydrogen storage alloy or in the vicinity thereof. It has an effect of generating active species as a catalyst on the surface of the hydrogen storage alloy.

For example, when a Mg ₂ Ni-based hydrogen storage alloy is treated with ethyl bromide, magnesium in the hydrogen storage alloy causes the following reactions.

Mg + C ₂ H ₅ Br → C ₂ H ₅ —MgBr (3) The oxide film covering the surface of Mg ₂ Ni is removed by the above reaction (surface modification), and at the same time hydrogen dissociation catalyst Since the nickel that acts as the surface appears on the surface, the occlusion characteristics are improved.

In addition to magnesium, the rare earth element Ln is used as an element that reacts with the RX compound.
(Ln: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, etc.). These Ln were dissolved in THF at room temperature under argon or nitrogen atmosphere in 1,2
-When reacted with diiodoethane, as shown in the following formula, L
nI ₂ is generated.

[0098] _{Ln + ICH 2 CH 2 I →} LnI 2 + CH 2 = CH 2 (4) in particular, among the rare earth elements, La, Nd, Sm, Lu is easy to react with 1,2-diiodoethane, its reactivity L
The order is a>Nd>Sm> Lu.

For example, LaNi ₅ type hydrogen storage alloy is
-When reacted with diiodoethane, lanthanum in the hydrogen storage alloy causes the following reaction.

[0100] _{La + ICH 2 CH 2 I →} LaI 2 + CH 2 = CH 2 (5) the reaction with the oxide film covering the surface of LaNi ₅ is removed by (surface modification), dissociation catalysts of the hydrogen during hydrogen occlusion Since the nickel that acts as the surface appears on the surface, the occlusion characteristics are improved.

Furthermore, after the treatment with the solvent in which the RX compound is dissolved, only a small amount of halogen remains (for example, 1% by weight or less) on the surface of the hydrogen storage alloy.
The original characteristics of the hydrogen storage alloy are not lost.

Another hydrogen storage alloy according to the present invention is Cu
In the X-ray diffraction peaks using Kα as the radiation source, the half-value width Δ (2θ) of at least one of the three strong lines is 0.
3 ° ≦ Δ (2θ) ≦ 10 °. here,
The three strong lines mean the peaks obtained by X-ray diffraction from the maximum peak to the third peak.

The composition system of the hydrogen storage alloy is, for example, the above-mentioned (1) AB ₅ system (for example, LaNi ₅ , CaNi).
₅ ), (2) AB ₂ system (eg MgZn ₂ , ZrNi ₂
Etc.), (3) AB type (for example, TiNi, TiFe, etc.),
(4) A ₂ B type (for example, Mg ₂ Ni, Ca ₂ Fe, etc.) can be mentioned.

Further, it is particularly preferable that the hydrogen storage alloy contains an alloy represented by the following general formula (IV).

Mg _2-x M2 _x M1 _y (IV) where M2 is an element capable of reacting exothermically with hydrogen, Al
And at least one element other than Mg selected from B, M1 is at least one element selected from the elements other than Mg and M2 and does not react exothermically with hydrogen, and x and y are each 0 ≦ x ≦ 1.0, 0.5 <
It is defined as y ≦ 2.5.

For M1, the same element as described for the alloy of the general formula (I) is used. For M2, the same element as described for the alloy of the general formula (II) is used.

In particular, Mg ₂ Ni-based or the above general formula (IV)
In a hydrogen storage alloy containing 10% or more of magnesium, such as the hydrogen storage alloy containing the alloy shown in Fig. 4, in the X-ray diffraction peak with CuKα as a radiation source, the apparent half-value width Δ (2θ ₁ ) Is 0.3 ° ≦ Δ (2θ
₁ ) ≦ 10 °, or apparent half width Δ (2θ ₂ ) at the peak around 40 ° is 0.3 ° ≦ Δ (2θ ₂ ).
It is preferable that ≦ 10 °.

The above-mentioned Δ (2θ) is defined for the following reason. When the above Δ (2θ) is less than 0.3 °, the hydrogen storage rate becomes extremely small. On the other hand, when Δ (2θ) exceeds 10 °, the storage amount of the hydrogen storage alloy decreases. From this, the range of Δ (2θ) is preferably 0.3 ° ≦ Δ (2θ) ≦ 10 °.

In the hydrogen storage alloy, it is preferable that the relationship of 0.8 nm ≦ D ≦ 50 nm is satisfied, where D is the crystallite size. In the hydrogen storage alloy having such a defined crystallite size, the path through which hydrogen diffuses is increased and the distance is shortened, so that the hydrogen storage / desorption characteristics are improved. The size of the crystallite is defined by
The reason is as follows. That is, when the D is less than 0.8 nm, the amount of hydrogen stored may be reduced. On the other hand, when D exceeds 50 nm, the hydrogen diffusion path is hindered.

On the surface of the hydrogen storage alloy, IVA, V, A, VIA, VIIA, VIIIA, IB, IIB, II
It is preferable that at least one element selected from Group IB and Group IVB, an alloy or a metal oxide composed of them be contained up to an equimolar ratio.

Another method for modifying the surface of a hydrogen storage alloy according to the present invention is to use a hydrogen storage alloy alone or a hydrogen storage alloy.
Group IVA, Group V A, Group VIA, Group VIIA, Group VIIIA, IB
Of a mixture of at least one element selected from Group IIIB, IIIB, IIIB, and IVB, an alloy composed of them, or a metal oxide in equimolar proportions, in a vacuum, an inert gas, or hydrogen. It is characterized by performing mechanical treatment in an atmosphere.

The element, alloy or metal oxide acts as a catalytic species for hydrogenation by forcibly adding to the hydrogen storage alloy. As the catalyst species, elements or alloys or metal oxides having a high catalytic activity for the reaction with hydrogen are preferable. That is, the heat of reaction with hydrogen is positive (endothermic type), or considering the application to a battery, the exchange current density i in the negative electrode (hydrogen electrode) reaction is i.
It is preferable that ₀ is large. Such elements include:
Group IVA, Group V A, Group VIA, Group VIIA, Group VIIIA, and Group IB elements, such as V, Nb, Ta, Cr, Mo,
W, Mn, Fe, Ru, Co, Rh, lr, Pd, N
i, Pt, Cu, Ag, Au and the like are preferable.

Further, group IVA, group V A, group VIA, group VII A
Among alloys composed of at least one element selected from Group I, Group VIIIA, Group IB, Group IIB, Group IIIB and Group IVB, due to the synergistic effect between the elements, the catalytic activity in the hydrogen electrode reaction is higher than that of the element alone. Those that form high alloys are preferred. For example, Ni-Ti alloy, Ni-Zr alloy, Co-Mo alloy, Ru-V alloy, Pt-W alloy, Pd-W alloy, Pt-Pd alloy, V-Co alloy, Examples thereof include V-Ni alloys, V-Fe alloys, Mo-Co alloys, Mo-Ni alloys, W-Ni alloys, and W-Co alloys. Among these alloys, especially MoC
O ₃ , WCo ₃ , MoNi ₃ , WNi _{3 and the} like have high catalytic activity and are suitable for improving the storage characteristics of the hydrogen storage alloy.

Further, among the metal oxides composed of the above elements, the exchange current density i ₀ is particularly large, such as Fe.
O, RuO ₂ , CoO, Co ₂ O ₃ , Co ₃ O ₄ , Rh
O ₂ , lrO ₂ , NiO and the like are preferable.

As the mechanical processing means, for example, a planetary ball mill, a screw type ball mill, a rotary type ball mill, a hydrogen storage alloy alone or a hydrogen storage alloy and the above-mentioned elements in a container containing balls such as an attritor A method is adopted in which a mixture of an alloy or a metal oxide composed of the above is charged, and the hydrogen storage alloy alone or a mixture is mechanically impacted by collision between the container and the ball or the ball and the ball.

The container is sealed in an apparatus such as a dry box filled with an atmosphere of an inert gas such as argon, or the container is provided with an exhaust valve to exhaust the inside of the container. In some cases, hydrogen gas may be introduced for the treatment. Since such a device causes a collision in a closed container, the joint of the container is also impacted, which is one of the causes of deterioration of the hermeticity. Therefore, in order to ensure the airtightness, it is preferable to devise a container such as a double lid, or to fill the device itself with an inert atmosphere or put it in a vacuumed room. In addition, when an inert atmosphere is used, it is preferable that the purity of the inert gas is also controlled. For example, it is preferable that the inert gas is suppressed to have an oxygen concentration of 100 ppm or less and a water concentration of 50 ppm or less. It is desirable to handle the hydrogen storage alloy powder or metal powder used as a raw material in an inert gas atmosphere to avoid oxidation.

Mechanical treatment with a planetary ball mill or the like is preferably carried out for 1 to 1000 hours. When the treatment time is less than 1 hour, the storage characteristics of the hydrogen storage alloy do not change sufficiently, while when it exceeds 1000 hours, the oxidation gradually progresses and the manufacturing cost increases.

The modified hydrogen storage alloy powder obtained by the mechanical treatment preferably has a particle size of 0.1 to 50 μm. Moreover, you may heat-process as needed. The treatment temperature depends on the composition of the hydrogen storage alloy, but is preferably in the temperature range of about 100 to 500 ° C. Further, in some cases, the element species mixed by the treatment may form an aggregate with the alloy, and the aggregating effect can also improve the occlusion characteristics. At that time, the aggregation ratio is preferably 10% by weight or more.

According to the method for modifying the surface of a hydrogen storage alloy according to the present invention described above, the hydrogen storage alloy alone or in the hydrogen storage alloy may be a group IVA, a group A, a group VIA, a group VIIA, or a group VIA.
A mixture obtained by mixing at least one element selected from the IIA group, the IB group, the IIB group, the IIIB group, and the IVB group, and an alloy or a metal oxide composed of them in an equimolar ratio under vacuum and an inert gas. Alternatively, by performing mechanical treatment in a hydrogen atmosphere, the initial activity and storage characteristics of the hydrogen storage alloy can be significantly improved.

As a method for improving the hydrogen storage characteristics of the hydrogen storage alloy, 1) coating modification, 2) topochemical modification, 3) mechanochemical modification, 4) encapsulation modification, and 5) radiation. Combination use of irradiation and the like can be mentioned. The surface modification method of the hydrogen storage alloy of the present invention focuses on the modification of 3) among these methods, and mechanically treats the hydrogen storage alloy to remarkably improve the initial activity and storage characteristics of the hydrogen storage alloy. It is an improvement.

The mechanical modification according to the present invention not only changes the basic structure of the particles, but also changes the physical properties of the particles by changing the surface structure. That is, it is possible to change the internal energy of the hydrogen storage alloy. Generates a fresh surface with the generation of finer particles,
It is also possible to increase its surface energy.

Further, the mechanical reforming according to the present invention changes the surface of the hydrogen storage alloy and its structure, and the stress generated there causes structural destruction. In addition, the displacement of atoms and molecules and the deterioration of regularity are caused. To increase the potential energy. By such an action, it is possible to improve the catalytic activity and the selectivity in the catalytic reaction.

On the other hand, one of the phenomena caused by the reforming is a lattice defect in the hydrogen storage alloy. Lattice defects include, in addition to the lattice defects that are thermodynamically allowed in an ideal crystal, plastic deformation caused in the particles by mechanical energy applied during the modification process, and particles generated by locally generated heat. It is considered that the residual stress caused by the temperature difference in the interior, the phase transition and the occurrence of the phase transition are included. These effects can also improve the hydrogen storage characteristics of the hydrogen storage alloy.

After mechanically modifying the hydrogen storage alloy, when the X-ray diffraction peak of the sample using CuKα as a radiation source was measured, the broadening of the profile was observed.
Generally, the broadening of the profile is caused by (a) a change in crystallite size and (b) non-uniform strain.

In (a) above, the crystallite size D is Sc
It can be shown using the Herr's formula as follows.

D = (0.9 · λ) / (Δ (2θ) cosθ) (6) D: size of crystallite, Δ (2θ): apparent half width λ: measured X-ray wavelength, θ: Bragg angle of diffraction line Similarly, using the Stokes & Wilson equation, the crystallite size ε is expressed as follows.

Ε = λ / (β _i cos θ) (7) ε: Crystallite size β _i : Integral width λ: Measurement X-ray wavelength θ: Bragg angle of diffraction line In a hydrogen storage alloy that has been mechanically treated , X-ray diffraction peak becomes broad. It is considered that this is because, from the above two equations, the crystallite becomes smaller when mechanical treatment is applied.

Further, the influence of the distortion of the crystallite in the above (b) must be sufficiently taken into consideration as the factor that the X-ray diffraction peak becomes broad. The lattice strain that appears here may be a change or variation in the interplanar spacing. Stokes & Wil
According to the Son's formula, the following relationship exists between the nonuniform strain η of the crystallite and the integral width β ′ _i of the diffraction line based on it.

Β ′ _i = 2ηtan θ (8) Further, the spread of the profile due to both the size of the crystallite and the nonuniform strain can be expressed by the following equation using the Hall equation.

Β = β _i + β ′ _i (9) Therefore, the spread of the profile in the mechanically treated hydrogen storage alloy is due to the contribution of both the change of the crystallite size and the generation of the nonuniform strain. Is.
These two factors can improve the occlusion characteristics of the alloy. That is, when the crystallites of the hydrogen storage alloy are reduced by mechanical treatment, the path through which hydrogen is diffused is increased and the distance is shortened. Therefore, the hydrogen absorption / desorption characteristics of the hydrogen storage alloy can be improved. The crystallite size D is preferably 0.8 nm ≦ D ≦ 50 nm as described above. Further, when the mechanical treatment is performed, the collision energy becomes so large as to change the interplanar spacing of the hydrogen-absorbing alloy particles, resulting in lattice mismatch in the hydrogen-absorbing alloy. That is, since the hydrogen storage alloy can be strained, it is possible to change the energy in the crystal lattice and facilitate the absorption and desorption of hydrogen.

Further, the hydrogen-absorbing alloy subjected to the mechanical treatment has an apparent half width Δ of the above-mentioned formula (6).
The spread of the profile represented by (2θ) is 0.3 ° ≦ Δ
(2θ) ≦ 10 °.

On the other hand, the activity of the hydrogen storage alloy during hydrogen storage is considered to be related to the ease of forming the catalyst layer on the surface and the performance of the catalyst. From these points, it is possible to improve the hydrogen storage characteristics of the hydrogen storage alloy by the above-mentioned action. In order to further improve hydrogen storage characteristics, the present invention provides a hydrogen storage alloy with a Group IVA, Group V A, Group VIA,
Group VIIA, Group VIIIA, Group IB, Group IIB, Group IIIB, IVB
At least one element selected from the group consisting of at least one element, an alloy composed of them, or a metal oxide is equimolarly mixed in a molar ratio, and this mixture is subjected to mechanical treatment in a vacuum, an inert gas or an atmosphere of hydrogen to produce hydrogen. The addition of a catalyst species in the conversion is performed. The mechanical treatment can forcibly add a catalyst species that serves as a hydrogenation catalyst to the alloy surface or in the vicinity thereof during storage, so that the initial activity can be improved. Therefore, according to such a surface modification method, the initial activity and storage characteristics of the hydrogen storage alloy can be significantly improved.

For example, the Mg ₂ Ni-based hydrogen storage alloy may be added to Ni.
Is mixed at a predetermined ratio and mechanically treated in an inert gas atmosphere such as argon, nickel acting as a hydrogen dissociation catalyst during storage is added to the surface layer. As a result, the storage characteristics of the hydrogen storage alloy can be improved. Further, the crystal grain size of the alloy decreases, the ratio of crystal grain boundaries increases, and non-uniform strain occurs in the crystal, so that hydrogen can be easily absorbed.

An example of a cylindrical nickel-hydrogen secondary battery among the alkaline secondary batteries according to the present invention will be described below with reference to FIG.

As shown in FIG. 3, an electrode group 5 made by stacking a positive electrode 2, a separator 3 and a negative electrode 4 and spirally winding them is housed in a cylindrical container 1 having a bottom. ing. The negative electrode 4 is disposed on the outermost periphery of the electrode group 5 and is in electrical contact with the container 1. The alkaline electrolyte is contained in the container 1. Hole 6 in the center
A circular first sealing plate 7 having a is disposed in the upper opening of the container 1. Ring-shaped insulating gasket 8
Is disposed between the periphery of the sealing plate 7 and the inner surface of the upper opening of the container 1, and the sealing plate 7 is attached to the container 1 via the gasket 8 by caulking to reduce the diameter of the upper opening inward. It is fixed airtightly. The positive electrode lead 9 has one end connected to the positive electrode 2 and the other end connected to the lower surface of the sealing plate 7. The hat-shaped positive electrode terminal 10 is mounted on the sealing plate 7 so as to cover the hole 6.
The rubber safety valve 11 includes the sealing plate 7 and the positive electrode terminal 1.
It is arranged so as to close the hole 6 in a space surrounded by 0. The circular holding plate 12 made of an insulating material having a hole in the center is arranged on the positive electrode terminal 10 such that the protruding portion of the positive electrode terminal 10 projects from the hole of the holding plate 12. The outer tube 13 covers the peripheral edge of the pressing plate 12, the side surface of the container 1, and the peripheral edge of the bottom of the container 1.

Next, the positive electrode 2, the negative electrode 4, the separator 3
The electrolytic solution will be described.

1) Positive Electrode 2 For this positive electrode 2, for example, a conductive material is added to nickel hydroxide powder as an active material, and the mixture is kneaded with a polymer binder and water to prepare a paste. It is prepared by filling a substrate, drying and molding.

Examples of the conductive material include cobalt oxide, cobalt hydroxide, metallic cobalt, metallic nickel and carbon.

Examples of the polymer binder include carboxymethyl cellulose, methyl cellulose, sodium polyacrylate and polytetrafluoroethylene.

The conductive substrate may be, for example, a net-like, sponge-like, fibrous or felt-like metal porous body formed of nickel, stainless steel or a metal plated with nickel.

2-1) Negative Electrode 4 In this negative electrode 4, a conductive material is added to the hydrogen storage alloy powder,
A paste is prepared by kneading with a polymer binder and water, filling the conductive substrate with the paste, and drying,
It is produced by molding.

The hydrogen storage alloy has the above-mentioned general formula (I).
Alternatively, a material containing an alloy represented by the general formula (II) is used.

In the X-ray diffraction peak with CuKα as the radiation source, the half-value width Δ (2θ) of at least one of the three strong lines is 0.3 ° ≦ Δ.
Those having (2θ) ≦ 10 ° are used. The hydrogen storage alloy has a crystallite size of 0.8,
It is preferable that the relationship of nm ≦ D ≦ 50 nm is satisfied.

As the polymer binder, the same ones as those used for the positive electrode 2 can be mentioned.

Examples of the conductive material include carbon black and the like.

The conductive substrate is, for example, a two-dimensional substrate such as punched metal, expanded metal, perforated rigid plate or nickel net, or a three-dimensional substrate such as a felt-like metal porous body or a sponge-like metal substrate. Can be mentioned.

Since the negative electrode containing the hydrogen storage alloy containing the alloys represented by the general formulas (I) and (II) as the negative electrode material has the optimized content ratio of magnesium or the like in the alloy. The reactivity can be improved, and the deterioration resistance, that is, the hydrogen storage / release of the hydrogen storage alloy or the stability during the charge / discharge cycle can be improved. Further, by providing such a negative electrode, it is possible to realize an alkaline storage battery having a large capacity and excellent charge / discharge characteristics.

2-2) Negative Electrode 4 This negative electrode is a negative electrode containing a hydrogen storage alloy containing magnesium, and (a) when it is immersed in an aqueous 6-8N alkali hydroxide solution. The elution rate of magnesium ions into the aqueous solution is 0.5 mg / kg alloy / hr or less, or the elution rate of magnesium ions into the alkali hydroxide aqueous solution at 60 ° C. is 4 mg / kg alloy / hr.
Or any of the following, and (b) the elution rate of the alloying element in the aqueous alkali hydroxide solution at room temperature is 1.5 mg /
kg alloy / hr or less, or the elution rate of alloying element in an alkali hydroxide aqueous solution at 60 ° C. is 20 mg / kg alloy /
It is either less than or equal to hr or either.

The present inventors have established a means for evaluating the deterioration rate of a hydrogen storage alloy containing magnesium, and based on this, a hydrogen storage alloy showing sufficient reversibility and stability for electrode reactions has been developed. The negative electrode containing was found.

The elution rate of ions of a hydrogen storage alloy in an aqueous solution of alkali hydroxide, that is, the corrosion rate is, so to speak, a parameter indicating the static stability of the alloy. Generally, this characteristic alone is the dynamic cycle stability. Cannot be estimated. This is because the cycle stability of hydrogen storage alloys depends on the static characteristics of the alloy itself, which are defined by chemical and physical alterations due to the addition of different elements, contact with different substances, surface treatment, etc. It is considered that this is because the contribution of dynamic characteristics such as the effect of strain applied to the lattice by hydrogen passing through the crystal lattice of the alloy is large.

Therefore, using hydrogen storage alloys having various compositions and various treatments with respect to magnesium-containing hydrogen storage alloys, a negative electrode (hydrogen electrode) was produced by several methods, and the characteristics were evaluated. As a result, at least reversibility was confirmed. It has been found that a high hydrogen storage alloy that satisfies the following conditions exhibits sufficient stability.

That is, as the condition for the negative electrode, when focusing only on magnesium, when immersed in an aqueous solution of 6-8 normal alkali hydroxide, (a) magnesium ions in the normal alkali hydroxide solution at room temperature are used. Dissolution rate of 0.5mg / kg alloy / hr, or dissolution rate of magnesium ion into alkaline hydroxide aqueous solution at 60 ° C is 4mg
/ Kg alloy / hr, and when paying attention to all the elements contained in the alloy, (b) the elution rate of the alloy component elements into the alkaline hydroxide aqueous solution at room temperature is 1.5 m.
g / kg alloy / hr, or the elution rate of alloying elements in an alkali hydroxide aqueous solution at 60 ° C. is 20 mg / kg alloy /
hr or either of them.

Here, the reason why the dissolution rate at 60 ° C. is adopted is that the ion elution rate at room temperature is very low, on the order of 0.5 mg / kg alloy / hour, in the alloy which can be put to practical use, and therefore the dissolution reaction The purpose is to increase speed and improve measurement time or accuracy.

Therefore, it is possible to perform evaluation by providing a prescribed value that shows substantially the same dissolution rate even at other temperatures. However, when the atmospheric temperature changes, side reactions may occur, and individual changes may occur depending on the type of alloy composition, treatment, etc. Therefore, it is not preferable to measure at a high temperature above 60 ° C.

As the easiest method for the negative electrode, when the hydrogen storage alloy itself is immersed alone in an aqueous solution of an alkali hydroxide having a normality of 6 to 10, the elution rate of magnesium ions into the electrolytic solution is room temperature. 0.5 mg / kg alloy / hour or less, 4 mg / kg alloy / hour or less at 60 ° C., and total elution rate of alloy component elements is 1.5 mg / k at room temperature
It is also possible to employ a method using a hydrogen storage alloy having a g alloy / hour or less and a 60 mg / kg alloy / hour or less of 20 mg / kg alloy / hour.

3) Separator 3 The separator 3 is made of a polymer non-woven fabric such as polypropylene non-woven fabric, nylon non-woven fabric, or non-woven fabric in which polypropylene fiber and nylon fiber are mixed. In particular, a polypropylene nonwoven fabric whose surface is hydrophilized is suitable as a separator.

4) Alkaline Electrolyte Solution Examples of the alkaline electrolyte solution include an aqueous solution of sodium hydroxide (NaOH) and lithium hydroxide (LiOH).
Aqueous solution of potassium hydroxide (KOH), NaO
H and LiOH mixture, KOH and LiOH mixture, K
A mixed solution of OH, LiOH, and NaOH can be used.

Another alkaline storage battery according to the present invention comprises a negative electrode containing a hydrogen storage alloy containing magnesium, which is housed in a container, and a positive electrode which is housed in the container and is sandwiched between the negative electrodes and a separator. An alkaline storage battery comprising an alkaline electrolyte contained in the container, wherein the alkali electrolyte is injected into the container to seal the container and then the alkali at a time of 30 days or more has elapsed. Magnesium ion concentration in the electrolyte is 2.2 mg
/ Liter or less.

Here, the reason why the ion concentration in the electrolytic solution is defined only when it is considered as an alkaline storage battery will be described below.

Generally, since the amount of the electrolytic solution in the alkaline battery is extremely limited, the ion concentration in the liquid tends to increase due to the elution of a small amount of ions, and the elution rate of the ions increases with the concentration of the eluted ions in the electrolytic solution. As the negative electrode (hydrogen electrode) has a slower deterioration rate, the ion concentration increase rate in the liquid becomes so small that it can be ignored in a relatively short time. Since the ion elution rate is low from the beginning, it can be considered that the ion concentration of the electrolytic solution in the storage battery is substantially constant after about 30 days from the injection. Therefore, with respect to the electrolytic solution inside the storage battery, the ion concentration as well as the ion elution rate can be regarded as a parameter.

According to another alkaline storage battery of the present invention described above, by establishing means for evaluating the deterioration rate of a hydrogen storage alloy containing magnesium, sufficient reversibility and stability for electrode reaction can be obtained. And a negative electrode containing a hydrogen storage alloy. Therefore, it becomes possible to provide an alkaline storage battery having a large capacity, which replaces the conventional alkaline storage battery (such as a nickel-cadmium battery or a nickel-hydrogen storage battery using a LaNi ₅ type hydrogen storage alloy).

It is considered that limiting the amount of magnesium ions eluted in the electrolytic solution in the alkaline storage battery is also effective in preventing internal short circuit due to dendrite formation.

The preferred embodiment will be described in detail below.

(Examples 1 to 5 and Comparative Examples 1 to 6) Mg
And Ni were melted and prepared in a high-frequency induction furnace in an argon atmosphere at atmospheric pressure to prepare 11 kinds of hydrogen storage alloys represented by Mg ₂ Ni _y and y having the values shown in Table 2 below.

The obtained 11 kinds of hydrogen storage alloys were made to have a particle size of 45.
Approximately 75 μm, and a certain amount of these alloys at 60 ° C, 8N
After being immersed in the aqueous potassium hydroxide solution for 5 hours, the concentration of magnesium ions eluted in this solution was measured.
From this measurement, the relative value of the dissolved magnesium concentration and the dissolved magnesium ion concentration per Mg mol of the alloy were obtained. The relative value of the eluted magnesium concentration was calculated by setting the eluted concentration from pure magnesium to 100. The results are also shown in Table 2 below. Further, FIG. 4 shows data obtained by dividing the elution amount by the ratio of magnesium contained in the alloy and normalizing the data.

Further, each of the above hydrogen storage alloys was pulverized to a particle size of 75 μm or less and placed in a pressure resistant container.
After introducing hydrogen gas under conditions of 0 ° C. and 10 atm, the amount of hydrogen stored in the alloy was calculated from the pressure decrease after 24 hours. The results are also shown in Table 2 below.

[0167]

[Table 2]

As is clear from Table 2, Mg ₂ Ni _y
In the hydrogen storage alloy represented by, the amount of eluted Mg ions is smaller than that of pure Mg when the Ni amount y is small, but when the y value exceeds 1.5, the eluted Mg ion amount is rapidly increased. It can be seen that it increases to. In particular, it can be seen that the amount of eluted Mg ions decreases in a hydrogen storage alloy in which y is 1.5 or less and exceeds 1. Further, in the hydrogen storage alloy represented by Mg ₂ Ni _y , the hydrogen storage amount does not change so much when the value of y, which is the amount of Ni, is around 1, but when the value of y exceeds 1.5, It can be seen that the storage characteristics sharply deteriorate. From these results, it is understood that the hydrogen storage alloy of the present invention in which the y value of Mg ₂ Ni _y is in the range of 1 <y ≦ 1.5 has excellent chemical stability and hydrogen storage characteristics.

(Example 6 and Comparative Example 7) Mg and N
i was melted and prepared in a high frequency induction furnace at atmospheric pressure in an argon atmosphere to prepare Mg ₂ Ni _1.15 (Example 6) and Mg ₂ Ni.
Two kinds of hydrogen storage alloy ingots represented by _0.84 (Comparative Example 7) were obtained.

Each of the hydrogen-absorbing alloy ingots was cut out using a diamond cutter to prepare five kinds of strip-shaped alloy pieces having the dimensions shown in Table 3 below. Since the scratches and irregularities on the surface of the strip-shaped alloy piece act as rupture promoting portions, the alloy piece surface is polished with a diamond paste of 0.3 μm for the purpose of preventing the promotion of rupture and then subjected to the next stress measurement. did. The maximum stress of each strip-shaped alloy piece was measured.
That is, as shown in FIG.
It is passed over two support bars 22 arranged in parallel at intervals, and the portion of the strip-shaped alloy piece 21 located in the center between the support bars 22 is pushed by an indenter 23 to obtain the force required to bend the strip-shaped alloy piece 21. The maximum stress was calculated from this force.

The maximum stress was calculated according to the following equation. That is, the width of the strip-shaped alloy piece is W (mm), the thickness is T (mm),
The distance between the support bars is 20 mm, and the force required for bending is f /
If N, then the maximum stress σ is expressed by the formula shown below.

[0172]

[Equation 1]

The maximum stress of each strip-shaped alloy piece (sample) obtained by such a method is also shown in Table 3 below.

[0174]

[Table 3]

As is clear from Table 3 above, M of Example 6
The strip-shaped alloy piece composed of the hydrogen storage alloy of g ₂ Ni _1.15 has a lower stress than that of the strip-shaped alloy piece composed of the hydrogen storage alloy of Mg ₂ Ni _0.84 of Comparative Example 7, and is excellent in pulverization and workability. I understand.

Incidentally, in the SEM (scanning electron microscope) photograph of the cross-section of the hydrogen storage alloy of Example 6 described above, most of it had a Mg ₂ Ni phase, and other phases composed of only Ni, and the Mg ₂ It was confirmed that a small amount of a high Mg content phase was present at the grain boundary of the Ni phase. Such an organization
It was also confirmed by EPMA (X-ray microanalyzer). In the hydrogen storage alloy of Example 6, the high Mg content phase was 8 to 9% of the whole, and the Mg ₂ Ni phase and the phase consisting of Ni were 90% or more. Comparative Example 7 described above
In a similar SEM photograph of the hydrogen storage alloy of No. ₂ , most of them have a Mg ₂ Ni phase and other phases consisting of only Ni, and a considerable amount of Mg content is high in the grain boundary of the Mg ₂ Ni phase. It was confirmed that phases were present. In the hydrogen storage alloy of Comparative Example 7, the high Mg content phase occupied 20% or more of the whole.

From the results of these Example 6 and Comparative Example 7, alloys showing a homogeneity (Mg ₂ Ni phase) in which the composition distribution of the cross section of the structure in the alloy is 90% or more compared with the area ratio of the cross section are chemical. It can be seen that it is preferable in terms of stability and mechanical workability.

(Examples 7 to 14 and Comparative Examples 8 to 10)
In the composition of _{Mg 2-x M2 x M1 y} , Mg 2-x M2 x
And 11 kinds of hydrogen storage alloy ingots having the components of M1 and x and y values shown in Table 4 below were obtained.

Strip-shaped alloy pieces having dimensions similar to those of the sample 2 of Example 6 were prepared from these hydrogen storage alloy ingots, and the maximum stress was determined from the same test apparatus shown in FIG. 5 and the above equation. The results are also shown in Table 4.

[0180]

[Table 4]

As is clear from Table 4, Mg _2-x M2
Example 7 in which the value of y exceeds 1 in the composition of _x M1 _y
~ 14 hydrogen storage alloys have a maximum stress of 30 × 10 ⁶ Nm ^-2
The value of y is 1 in the above composition.
The maximum stress of the hydrogen storage alloys of Comparative Examples 8 to 10 below is 50.
It can be seen that a force of about 10 ⁶ Nm ⁻² , which is several tens of percent higher than that of the hydrogen storage alloys of Examples 7 to 14, is required.

Example 15 A hydrogen storage alloy represented by Mg ₂ Ni _y was prepared from a molten metal containing predetermined amounts of Mg and Ni by a slow cooling method. Subsequently, this alloy was sealed in a quartz tube in an argon atmosphere, and slowly annealed at 500 ° C. for about one month, so that y was 1.01.
A hydrogen storage alloy of g ₂ Ni _1.01 was obtained.

The obtained hydrogen storage alloy was immersed in an alkaline aqueous solution, and the amount of eluted magnesium ions was measured. As a result, the amount of relative eluted magnesium ions was 9, and the value obtained by dividing the magnesium content in the alloy by 66.4% was 0.14, indicating excellent chemical stability.

FIG. 6 is a schematic diagram showing a temperature scanning type hydrogen storage / release characteristic evaluation apparatus used for evaluation of hydrogen storage alloys of Example 16 and thereafter. The hydrogen cylinder 31 is connected to the sample container 33 through a pipe 32. The pipe 32 is branched on the way, and the end of the branch pipe 34 is connected to a vacuum pump 35. The pressure gauge 36 is attached to a pipe portion further branched from the branch pipe 34. First and second valves 37 ₁ and 37 ₂ are provided in the pipe 32 portion between the hydrogen cylinder 31 and the sample container 33 from the cylinder 31 side. Accumulator container 38
Is connected to the portion of the pipe 32 between the _first and second valves 37 ₁ and 37 ₂ . A third valve 37 ₃ is interposed in the branch pipe 34 portion between the vacuum pump 35 and the pressure gauge 36. The heater 39 is attached to the sample container 33. The thermocouple 40 is inserted in the sample container 33. The temperature controller 42 controlled by the computer 41 is connected to the thermocouple 40 and the heater 39, and adjusts the temperature of the heater 39 based on the detected temperature from the thermocouple 40. A recorder 43 controlled by the computer 41 is connected to the pressure gauge 36 and the temperature controller 42.

(Examples 16 and 17 and Comparative Example 11) M
g _2-x M2 _x M1 _y , M1 = Ni, M2 = Al,
Mg _1.9 Al _0.1 Ni with x = 0.1 and y = 105
_1.05 (Example 16), M1 = Ni, M2 in the same general formula
= Al, x = 0.1, y = 1 Mg _1.9 Al _0.1 N
i (Comparative Example 11), M1 = Ni, M2 = Mn, x = 0.
11, Mg _1.9 Mn _0.1 Ni with y = 1.05
A hydrogen storage alloy of _1.05 (Example 17) and Mg ₂ Ni (Comparative Example 3) was prepared.

Next, each of the hydrogen storage alloys was stored in the sample container 33 shown in FIG. Closing the first valve 37 _1, second and third opening the valve 37 _2, 37 _3, the pipe by operating the vacuum pump 35 32, and the branch pipe 34,
The air in the accumulator container 38 and the sample container 33 was exhausted.
The second, third after closing the valve 37 _2, 37 _3, the pipe 32 and branch pipe 34 to supply hydrogen from the first hydrogen cylinder 31 by opening the valve 37 _1, accumulating container 38 and sample container 33 The inside was replaced with hydrogen. Subsequently, the first valve 37 ₁ was closed, and the amount of hydrogen introduced at this point was calculated from the pressure in the system indicated by the pressure gauge 36. Continued, second
The valve 37 ₂ was opened, hydrogen was supplied into the sample container 3, and the temperature was monitored by the thermocouple 40. After that, the temperature inside the sample container 33 was controlled by the computer 41 and the temperature controller 42 so as to increase at a constant rate, and the temperature was scanned using the heater 39 which received the control signal. The pressure change in the container 33 at this time is measured by the pressure gauge 3
6 and recorded it on the recorder 43. FIG. 7 shows the pressure change due to the temperature rise of the sample container 33 (the pressure decrease due to the hydrogen storage of the hydrogen storage alloy).

[0187] Mg _1.9 Al _0.1 Ni _1.05 of hydrogen storage alloy from 7 (Example 16), it can be seen that absorb hydrogen at low temperature as compared with the Mg _{1. 9} Al _0.1 Ni hydrogen-absorbing alloy (Comparative Example 11) . Further, it can be seen that the hydrogen storage alloy of Mg _1.9 Mn _0.1 Ni _1.05 (Example 17) can store hydrogen at a lower temperature than the hydrogen storage alloy of Mg ₂ Ni (Comparative Example 3). In particular, it can be seen that the hydrogen storage alloy of Example 16 in which M2 is Al can further lower the storage temperature as compared with the same alloy of Example 17 in which M2 is Mn. Also,
It can be seen that the hydrogen storage alloys of Examples 16 and 17 have the same hydrogen storage capacity as the hydrogen storage alloy of Mg ₂ Ni (Comparative Example 3). Therefore, it is understood that by replacing Mg with M2 (Al or Mn), it is possible to achieve a lower storage temperature while maintaining a high hydrogen storage amount.

Furthermore, Mg _1.9 Al _0.1 Ni _1.05 , Mg
Hydrogen storage alloy of _1.9 Mn _0.1 Ni _1.05 (Examples 16, 1
7) and Mg _1.9 Al _0.1 Ni, Mg ₂ Ni hydrogen storage alloys (Comparative Examples 11 and 3), the relationship between the stored hydrogen concentration and temperature was investigated, and H / M = 0.1 (the number of hydrogen storage alloy atoms). (Meaning that the ratio of the number of occluded atoms to 0.1 is 0.1) was investigated. Further, the relative values of the eluted magnesium concentration of the hydrogen storage alloys of Examples 16 and 17 and Comparative Examples 11 and 3 and Mg of the alloys
The dissolved magnesium ion concentration per mol was measured by the same method as in Example 1 described above. The relative value of the eluted magnesium concentration was calculated by setting the eluted concentration from pure magnesium to 100. The results are shown in Table 5 below.

[0189]

[Table 5]

As is clear from Table 5, Mg is added to M2.
It can be seen that the hydrogen storage alloy having a composition in which the value of y of M1 exceeds 1 while substituting with (Al or Mn) can achieve a lower storage temperature and further improve chemical stability.

[0191] (Example _{18) Mg 2-x M2 x} M1 y in M1 = Ni, Co, M2 = Al, x = 0.1, y =
Using Mg _1.9 Al _0.1 Ni _0.55 Co _0.55 of 1.10, the temperature scanning type hydrogen absorption / desorption characteristics evaluation apparatus shown in FIG. The pressure decrease due to hydrogen storage of the hydrogen storage alloy) was measured. As a result, the characteristic diagram shown in FIG. 8 was obtained. Note that FIG. 8 also shows the results of the hydrogen storage alloy of Mg ₂ Ni described above (Comparative Example 3).

As is clear from FIG. 8, M1 is Ni or Co.
It can be seen that the hydrogen storage alloy, which is, can achieve a lower storage temperature while maintaining a high hydrogen storage amount.

Further, the relative value of the eluted magnesium concentration of the hydrogen storage alloy of Example 18 and the eluted magnesium ion concentration per Mg mol of the alloy were measured by the same method as in Example 1 described above. The relative value of the eluted magnesium concentration was calculated by setting the eluted concentration from pure magnesium to 100. As a result, the relative value of the eluted magnesium ion concentration was 8, and the eluted magnesium ion concentration per mol of Mg of the alloy was 0.13.

(Examples 19 and 20 and Comparative Example 12) M
_{In 2-x} M2 _x M1 _y , M = Zr, M1 = Fe, M2
= V, x = 0.1, y = 1.05, Zr _1.9 V _0.1
Fe _1.05 (Example 19), M = Zr, M in the general formula
Zr _1.9 Cr _0.1 Fe _1.05 (Example 20) and Zr with 1 = Fe, M2 = Cr, x = 0.1, y = 10.5
FIG. 6 showing the hydrogen storage alloy of ₂ Fe (Comparative Example 12).
Using the temperature scanning type hydrogen storage / release characteristic evaluation apparatus shown in FIG. 5, the pressure change due to the temperature rise of the sample container (pressure decrease due to hydrogen storage of hydrogen storage alloy) was measured by the same method as in Example 16, and H / M = 0.1 (meaning that the ratio of the number of stored atoms to the number of hydrogen storage alloy atoms is 0.1) was determined. The results are shown in Table 6 below.

[0195]

[Table 6]

As is clear from Table 6, M is Zr,
A hydrogen storage alloy having a composition in which Zr is replaced by M2 (V, Cr) and the y value of M1 exceeds 1 (Examples 19 and 2)
In 0), it can be seen that the storage temperature can be lowered.

(Examples 21 to 26 and Comparative Examples 13 and 1)
4) First, Mg, Ni, Ag, Cd, Ca, Pd, A
l, In, Co, and Ti were melted and prepared in a high-frequency induction furnace under an atmospheric pressure and an argon atmosphere to prepare nine types of hydrogen storage alloys represented by Mg _2-x M2 _x M1 _y shown in Table 7 below.

Next, each of the hydrogen storage alloys to be used as a sample was housed in the sample container 23 shown in FIG. Closing the first valve 37 _1, No. 2, opens the third valve 37 _2, 37 _3, and operating the vacuum pump 35 exhausts the air in the pipe 32 and the branch pipe 34, the pressure accumulator 38 and the sample container 33 did. After the second and third valves 37 ₂ and 37 ₃ are closed, the first valve 37 ₁ is opened to supply hydrogen from the hydrogen cylinder 31 to replace the pipe 32, the branch pipe 34, and the pressure accumulator 38 with hydrogen. did. Next, the first pipe 3
7 ₁ is closed, the second valve 37 ₂ is opened, hydrogen is supplied to the sample container 33, and the pressure and temperature recorded in the recorder 39 are confirmed.

In Examples 21 to 26, the pressure of the hydrogen cylinder 1 which is different from that of the pressure accumulating vessel is set so that the pressure (initial pressure) becomes about 10 atm, and the measurement start temperature is Room temperature (about 25 ° C.) was used.

Thereafter, the temperature inside the sample container 33 is controlled by the computer 41 and the temperature controller 42 so as to increase at a rate of 0.5 ° C./min, and the temperature is controlled by using the heater 39 which receives the control signal. I had it scanned. The temperature change and the pressure change in the sample container 33 at this time were detected by the thermocouple 40 and the pressure gauge 36 and recorded by the recorder 43.

The pressure inside the sample container 33, which changes with temperature rise, is monitored by the above operation, and from the pressure drop, M / H = 0.1, that is, the number of stored hydrogen atoms per mole of metal atom of the alloy is 0. The temperature at the time when the temperature reached 1 was determined and used as a standard for the minimum temperature at which the hydrogen storage alloy can perform the hydrogen storage reaction. In addition, Examples 21 to 26 and Comparative Example 3,
The relative values of the eluted magnesium concentrations of the hydrogen storage alloys 13 and 14 and the eluted magnesium ion concentration per Mg mol of the alloy were measured by the same method as in Example 1 described above. The relative value of the eluted magnesium concentration was calculated by setting the eluted concentration from pure magnesium to 100. The results are also shown in Table 7 below.

[0202]

[Table 7]

As is clear from Table 7, Examples 21 to 21
It can be seen that the hydrogen storage alloy of No. 26 can lower the hydrogen storage temperature and can further improve the chemical stability as compared with the hydrogen storage alloys of Comparative Examples 3, 13, and 14.

(Example 27) An argon gas introduction tube, a dropping funnel and an Arene cooling tube were attached to a round bottom flask containing a rotor, Mg ₂ Ni hydrogen storage alloy was put into the round bottom flask, and the pressure was reduced by a vacuum pump. After heating and drying with a heat gun, the atmosphere was replaced with argon. Subsequently, THF was added to the round-bottomed flask while flowing argon, and 1-bromo-3-ethane was slowly added dropwise from a dropping funnel with sufficient stirring to obtain the hydrogen storage alloy and 1-bromo-3-ethane. The reaction was started. After the dropping, stop stirring,
A surface-modified hydrogen storage alloy was obtained by precipitating and filtering the hydrogen storage alloy.

The hydrogen storage characteristics of the obtained surface-modified hydrogen storage alloy and the hydrogen storage alloy before surface modification were measured using the hydrogen storage / release characteristics evaluation device shown in FIG.
The measurement was performed by monitoring the pressure change in the reaction container when a certain amount of hydrogen was introduced into the reaction container.

First, the hydrogen storage alloys were housed in the sample container 33 shown in FIG. The first valve 37 ₁ is closed,
The third valves 37 ₂ and 37 ₃ were opened, and the vacuum pump 35 was operated to sufficiently exhaust the air in the pipe 32, the branch pipe 34, the pressure accumulating container 38 and the sample container 33. After closing the second and third valves 37 ₂ and 37 ₃ , the first valve 37
₁ was opened and hydrogen was supplied from the hydrogen cylinder 31 to replace the inside of the pipe 32, the branch pipe 34 and the pressure accumulator 38 with hydrogen. Then, the first valve 37 ₁ was closed, and the amount of hydrogen introduced was calculated from the pressure in the system indicated by the pressure gauge 36 at that time. Subsequently, the second valve 37 ₂ is opened, hydrogen is supplied into the sample container 33, and the temperature is monitored by the thermocouple 40. At that time, the heater 39 was controlled by the computer 41 and the temperature controller 42 so that the temperature in the sample container 33 was kept constant. The pressure change in the container 23 at this time was detected by the pressure gauge 36 and recorded by the recorder 43.

FIG. 9 shows changes in pressure due to hydrogen storage at 25 ° C. in the Mg ₂ Ni hydrogen storage alloy before and after surface modification (pressure decrease due to hydrogen storage of the hydrogen storage alloy).

As is clear from FIG. 9, when a constant hydrogen pressure is applied, no pressure change occurs in the Mg ₂ Ni hydrogen storage alloy before surface modification, and the constant pressure is maintained. On the other hand, it can be confirmed that in the surface-modified Mg ₂ Ni hydrogen storage alloy, the pressure in the system changes abruptly and a large amount of hydrogen is stored. This is also about 200 ° C lower than the temperature required for conventional storage. That is, Mg ₂ Ni
Hydrogen storage alloys do not undergo storage / release reactions (or are extremely slow) unless they are processed at relatively high temperatures (about 200 to 300 ° C.). In contrast, the surface-modified hydrogen storage alloy of Example 27 was able to store hydrogen near room temperature.

(Examples 28 to 59) The hydrogen storage alloys having the compositions shown in Tables 8 to 10 below were subjected to surface modification in the same manner as in Example 27, and the hydrogen storage alloys before and after the surface modification were carried out at 25 ° C. Was evaluated using the hydrogen storage / release characteristics evaluation device shown in FIG. The results are also shown in Tables 8 to 10 below. It should be noted that X in Tables 8 to 10 represents the number MH _X of hydrogen stored in the hydrogen storage alloy.

[0210]

[Table 8]

[0211]

[Table 9]

[0212]

[Table 10]

As is clear from Tables 8 to 10, it can be seen that the surface modification of the hydrogen storage alloy activates the surface to improve the hydrogen storage characteristics.

(Example 60) An Mg ₂ Ni hydrogen storage alloy was placed in a stainless steel container with a double lid together with stainless steel balls, and the oxygen concentration was 1 ppm or less and the water concentration was 0.
Fill with an argon atmosphere controlled to 5 ppm or less, and
After sealing the container with a ring, a ball mill (mechanical treatment) was performed at a rotation speed of 200 rpm for 100 hours.

The hydrogen storage characteristics of the mechanically treated hydrogen storage alloy and the untreated hydrogen storage alloy were measured using the hydrogen storage / release characteristic evaluation apparatus shown in FIG. The measurement was performed by monitoring the pressure change in the reaction container when a certain amount of hydrogen was introduced into the reaction container.

First, the hydrogen storage alloys shown in FIG.
The sample container 33 was stored. Closing the first valve 37 _1, to open the second, third valve 37 _2, 37 _3, the pipe 32 by operating the vacuum pump 35, the branch pipe 34, the air in the accumulator vessel 38 and sample vessel 33 sufficient Exhausted to. After closing the second and third valves 37 ₂ and 37 ₃ , the first valve 37 ₁ was opened to supply hydrogen from the hydrogen cylinder 31 to replace the inside of the pipe 32, the branch pipe 34 and the pressure accumulator 38 with hydrogen. . Then, the first valve 37 ₁ was closed, and the amount of hydrogen introduced was calculated from the pressure in the system indicated by the pressure gauge 36 at that time. Subsequently, the second valve 37 ₂ is opened, hydrogen is supplied into the sample container 33, and the temperature is monitored by the thermocouple 40. At that time, the heater 39 was controlled by the computer 41 and the temperature controller 42 so that the temperature in the sample container 33 was kept constant. The container 3 at this time
The pressure change in 3 was detected by the pressure gauge 36 and recorded by the recorder 43.

Table 11 shows the evaluation results of the hydrogen storage characteristics at 25 ° C. of the hydrogen storage alloy powder before and after the mechanical treatment.

(Example 61) 0.5 mol of Mg ₂ Ni hydrogen storage alloy and 0.5 mol of Ni powder as a catalyst seed were mixed, and this mixture was placed in a stainless steel container with a double lid and made of stainless steel. It is put together with a ball, filled with an argon atmosphere controlled to have an oxygen concentration of 1 ppm or less and a water concentration of 0.5 ppm or less, and the container is sealed with an O-ring, and then a ball mill (mechanical treatment) is run at 200 rpm for 1 minute.
I went for 00 hours.

The hydrogen storage characteristics of the mechanically treated hydrogen storage alloy and the untreated Mg ₂ Ni hydrogen storage alloy were evaluated by the same method as in Example 60 using the hydrogen storage / release characteristic evaluation apparatus shown in FIG. did. The evaluation results of hydrogen storage characteristics at 25 ° C. are also shown in Table 11 below.

(Examples 62 to 92) Tables 11 to 13 below.
The hydrogen storage alloy having the composition shown in FIG. 6 was mechanically treated in the same manner as in Example 60, and the hydrogen storage / desorption characteristic evaluation device shown in FIG. 6 was used to measure the storage characteristics of each hydrogen storage alloy before and after mechanical treatment at 25 ° C. Evaluated. The results are also shown in Tables 11 to 13 below. In addition, Table 1
X in 1 to Table 13 represents the number MH _X of hydrogen stored in the hydrogen storage alloy.

[0221]

[Table 11]

[0222]

[Table 12]

[0223]

[Table 13]

As can be seen from Tables 11 to 13, it is understood that the mechanical treatment of the hydrogen storage alloy activates the surface and improves the hydrogen storage characteristics.

(Example 93) The hydrogen-absorbing alloy powder obtained in Example 61 and electrolytic copper powder were mixed in a weight ratio of 1: 1 and 1 g of this mixture was tableted (inner diameter: 10 m).
Pellets were produced by pressurizing with mφ) at a pressure of 20 tons for 3 minutes. The pellet was sandwiched by a nickel wire mesh, the peripheral portion was spot-welded and pressure-welded, and a nickel lead wire was spot-welded to produce a hydrogen storage alloy electrode (negative electrode).

(Comparative Example 15) A hydrogen storage alloy electrode (negative electrode) was prepared in the same manner as in Example 93, except that the Mg ₂ Ni hydrogen storage alloy powder that had not been mechanically treated was used.

The negative electrodes of Example 93 and Comparative Example 15 were each immersed in an aqueous 8N potassium hydroxide solution together with a counter electrode of a sintered nickel electrode, and a charge / discharge cycle test was conducted at a temperature of 25 ° C. Charge / discharge conditions are as follows: 1 hour after charging with a current of 100 mA / g of hydrogen storage alloy for 10 hours.
A cycle of resting for 0 minute and discharging at a current of 20 mA per gram of hydrogen storage alloy to −0.5 V with respect to the mercury oxide electrode was repeated. The result is shown in FIG. Incidentally, A in FIG. 10 is Mg ₂ N without mechanical treatment.
i is the charge / discharge characteristic line of Comparative Example 15 using the negative electrode containing the hydrogen storage alloy, and B is the charge / discharge characteristic line of Example 93 using the negative electrode containing the mechanically treated hydrogen storage alloy.

As is apparent from FIG. 10, in Comparative Example 15 (characteristic line A), charging / discharging cannot be performed at room temperature, and almost no discharge capacity is shown. On the other hand, in Example 93,
(Characteristic line B) shows discharge capacity of 750 mA from the first cycle
h / g is shown, and the discharge capacity can be remarkably increased by the mechanical treatment. Therefore, the mechanical treatment is a very effective method that can significantly improve the discharge characteristics of the storage battery provided with the negative electrode containing the hydrogen storage alloy.

(Examples 94 to 97 and Comparative Example 15) M
g ₂ Ni hydrogen storage alloy was placed in a stainless steel container with a double lid together with stainless steel balls, and the oxygen concentration was 1 p
After filling with an argon atmosphere controlled to pm or less and a water concentration of 0.5 ppm or less and sealing the container with an O-ring, a ball mill (mechanical treatment) at a rotation speed of 200 rpm for 2 hours, 50 hours, 200 hours and 800 hours. Each was performed to obtain four kinds of surface-modified hydrogen storage alloy powder.

By using each of the obtained surface-modified hydrogen storage alloy powders and Mg ₂ Ni hydrogen storage alloy powders without mechanical treatment (Comparative Example 15), a hydrogen storage alloy electrode (negative electrode) was prepared in the same manner as in Example 93. Was produced. Each of these negative electrodes was immersed in an aqueous 8N potassium hydroxide solution together with a counter electrode of a sintered nickel electrode, and a charge / discharge cycle test was performed under the same conditions as in Example 93 at a temperature of 25 ° C.
The maximum discharge capacity was measured. The results are shown in Table 14 below. The average particle size of the hydrogen storage alloy powder used is also shown in Table 14 below.

[0231]

[Table 14]

As is clear from Table 14, as the mechanical treatment time is increased, the average particle size of the hydrogen storage alloy powder becomes smaller and the discharge capacity can be increased.

(Examples 98 to 101 and Comparative Example 15)
The Mg ₂ Ni hydrogen storage alloy was placed in a stainless steel container with a double lid together with stainless steel balls, and the oxygen concentration was set to 1
After filling with an argon atmosphere controlled to be ppm or less and a water concentration of 0.5 ppm or less, and sealing the container with an O-ring, a ball mill (mechanical treatment) was performed at a rotation speed of 200 rpm for 3 hours, 40 hours, 300 hours, and 650 hours. Each was performed to obtain four kinds of surface-modified hydrogen storage alloy powder.

A hydrogen storage alloy electrode (negative electrode) was prepared in the same manner as in Example 93, using the obtained surface-modified hydrogen storage alloy powder and the Mg ₂ Ni hydrogen storage alloy powder that was not mechanically treated (Comparative Example 15). Was produced. Each of these negative electrodes was immersed in an aqueous 8N potassium hydroxide solution together with a counter electrode of a sintered nickel electrode, and a charge / discharge cycle test was performed under the same conditions as in Example 93 at a temperature of 25 ° C.
The maximum discharge capacity was measured. The results are shown in Table 15 below. In addition, in Table 15 below, Δ (2θ ₂ ) of the hydrogen-absorbing alloy powder used [half-width of at least one of the three strong lines in the X-ray diffraction peak using CuKα as a radiation source] is also shown. .

[0235]

[Table 15]

As is clear from Table 15, as the mechanical treatment time is increased, the crystallites of the hydrogen storage alloy powder become smaller and the non-uniform strain is generated in the hydrogen storage alloy. Therefore, Δ (2θ ₂ ) It can be seen that the value increases and the discharge capacity can be increased.

(Examples 102 to 106 and Comparative Example 1)
5) The Mg ₂ Ni hydrogen storage alloy was put into a stainless steel container with a double lid together with stainless steel balls, filled with an argon atmosphere controlled to have an oxygen concentration of 1 ppm or less and a water concentration of 0.5 ppm or less, and the O-ring was used for the container. After sealing, the ball mill (mechanical treatment) was rotated at 200 rpm for 0.5 hours, 2.5 hours, 15 hours, 250
Time and 700 hours respectively to obtain 5 kinds of surface modified hydrogen storage alloy powder.

By using each of the obtained surface-modified hydrogen storage alloy powder and the Mg ₂ Ni hydrogen storage alloy powder not subjected to mechanical treatment (Comparative Example 15), a hydrogen storage alloy electrode (negative electrode) was prepared in the same manner as in Example 93. Was produced. Each of these negative electrodes was immersed in an aqueous 8N potassium hydroxide solution together with a counter electrode of a sintered nickel electrode, and a charge / discharge cycle test was performed under the same conditions as in Example 93 at a temperature of 25 ° C.
The maximum discharge capacity was measured. The results are shown in Table 16 below. The size of the crystallite of the hydrogen storage alloy powder used is also shown in Table 16 below.

[0239]

[Table 16]

As is clear from Table 16, as the mechanical treatment time is increased, the crystallites of the hydrogen storage alloy powder become smaller, which also increases the discharge capacity.

(Examples 107 to 113) The Mg ₂ Ni hydrogen storage alloy was placed in a container made of stainless steel with a double lid together with balls made of stainless steel, and vacuum, inert gas (argon, nitrogen, helium), hydrogen, oxygen or It was filled with a total of seven atmospheres of air. O in each atmosphere
After sealing the container with a ring, a ball mill (mechanical treatment) was performed at a rotation speed of 200 rpm for 100 hours to obtain seven kinds of surface-modified hydrogen storage alloy powder.

Using each of the surface-modified hydrogen storage alloy powders thus obtained, a hydrogen storage alloy electrode (negative electrode) was produced in the same manner as in Example 93. Each of these negative electrodes was immersed in an aqueous 8N potassium hydroxide solution together with a counter electrode, a sintered nickel electrode, and subjected to a charge / discharge cycle test under the same conditions as in Example 93 at a temperature of 25 ° C. to determine the maximum discharge capacity. It was measured. The results are shown in Table 17 below.

[0243]

[Table 17]

As is clear from Table 17, it is preferable that the mechanical treatment is carried out in an atmosphere of vacuum, inert gas or hydrogen, and it can be seen that the discharge capacity can be remarkably increased by the mechanical treatment in these atmospheres.

(Examples 114 to 160 and Comparative Example 1)
5) As shown in Tables 18 to 20 below, the hydrogen storage alloys were subjected to mechanical treatment under various conditions for surface modification, and a negative electrode containing these hydrogen storage alloys was prepared by the same method as in Example 93 above. Furthermore, each of these negative electrodes was immersed in an aqueous 8N potassium hydroxide solution together with a counter electrode of a sintered nickel electrode, and a charge / discharge cycle test was performed under the same conditions as in Example 93 at a temperature of 25 ° C. to determine the maximum discharge capacity. Was measured. The results are shown in Tables 18 to 20 below.

[0246]

[Table 18]

[0247]

[Table 19]

[0248]

[Table 20]

As can be seen from Tables 18 to 20, it is possible to increase the discharge capacity by subjecting the hydrogen storage alloy to a mechanical treatment, and the charge / discharge characteristics are remarkably improved.

(Examples 161-166 and Comparative Example 16)
-18) After mixing carbon powder and polytetrafluoroethylene in various amounts with a hydrogen storage alloy having a composition of Mg _1.9 Al _0.1 Ni _1.05, a sheet is formed by a roll, and these are pressed into a nickel wire mesh to form 9 kinds of materials. A hydrogen electrode (negative electrode) was produced. The water repellency of these hydrogen electrodes changes depending on the composition ratio such as the addition amount of polytetrafluoroethylene and the pressure when processing the pressure-bonded sheet, but the ion elution rate of the hydrogen storage alloy also changes.

Each of the obtained hydrogen electrodes was immersed in a potassium hydroxide aqueous solution having a normality of 8 and charged and discharged at room temperature. The charging condition was a current of 100 mA / g alloy for 10 hours, and the discharging condition was a current of 20 mA / g alloy based on mercury-mercury oxide electrode standard.
Up to 0.5V. Table 21 below shows the relationship between the ratio of the capacity at the 20th cycle and the capacity at the 3rd cycle and the ion elution rate when charging and discharging were repeated by this method. The ion elution rate was determined by immersing the hydrogen electrode in an alkali hydroxide aqueous solution for 5 hours and quantifying the amount of the elution component by inductively coupled plasma spectroscopy. The amount of the alkali hydroxide aqueous solution was about 100 ml per 1 g of the alloy in the hydrogen electrode.

[0252]

[Table 21]

(Examples 167 to 175) Carbon powder and polytetrafluoroethylene were mixed in various amounts with a hydrogen storage alloy having the composition shown in Table 22 below, and the mixture was formed into a sheet with a roll, and these were pressed onto a nickel wire mesh. By 9
A seed hydrogen electrode (negative electrode) was prepared.

Each of the obtained hydrogen electrodes was immersed in an aqueous potassium hydroxide solution of 8 normality, charged and discharged at room temperature under the same conditions as in Example 161, and the 20th cycle and 3rd cycle when the charging and discharging were repeated. Table 22 below shows the relationship between the capacity ratio at the cycle and the ion elution rate obtained by the same method as in Example 161.
Shown in

[0255]

[Table 22]

As is clear from Tables 21 and 22, (a) the elution rate of magnesium ions into an aqueous alkali hydroxide solution at room temperature is 0.5 mg / kg alloy / hr or less, or an aqueous alkali hydroxide solution at 60 ° C. The elution rate of magnesium ion into the alloy is 4 mg / kg alloy / hr or less, and (b) the elution rate of alloying element into the aqueous alkali hydroxide solution at room temperature is 1.5 mg / kg alloy /
Equipped with a hydrogen electrode (Examples 161 to 175) containing a hydrogen storage alloy having an elution rate of an alloy component element in an aqueous solution of alkali hydroxide of 60 ° C. of 20 mg / kg alloy / hr or less. The simulated cell is a hydrogen electrode containing a hydrogen storage alloy that deviates from the above conditions (Comparative Examples 16 to 1).
It can be seen that it has a higher capacity than the simulated cell with 8).

(Examples 176 to 184 and Comparative Example 1)
9) Examples 161, 167, 168, 169, 172,
The hydrogen electrodes (negative electrodes) used in 173, 174 and Comparative Example 18 were overlaid on a paste type nickel electrode (positive electrode) via a nylon non-woven fabric, and then wound into a cylindrical shape to prepare eight types of electrode groups. By inserting these electrode groups into an AA size battery container, injecting 8 N potassium hydroxide, and then sealing with a sealing plate equipped with a safety valve, as shown in FIG.
5 types of AA type nickel-metal hydride storage batteries shown in FIG.

The obtained storage batteries were charged under a charging condition of 50 mA / g.
Charging and discharging were repeated under the conditions of the alloy current for 10 hours and the discharge condition of 20 mA / g alloy current up to the battery voltage of 0.9 V, and the discharge capacities at the third cycle and the 20th cycle were compared. Further, the battery was decomposed 30 days after its production, and the amount of Mg ions in the electrolytic solution was analyzed by inductively coupled plasma spectroscopy. The results are shown in Table 23 below.

[0259]

[Table 23]

As is clear from Table 23, the magnesium ion concentration in the alkaline electrolyte after the injection of the alkaline electrolyte and sealing the container for 30 days or more was 2.2 mg / liter or less. Example 17
It can be seen that the storage batteries of Nos. 5 to 181 have a higher capacity than the storage battery of Comparative Example 19 which deviates from the above conditions.

[0261]

As described above in detail, the hydrogen storage alloy according to the present invention is excellent in low-temperature storage characteristics and chemical stability in addition to the original characteristics of being lightweight, large capacity, and low price. Various application fields that have used other alloy systems (hydrogen storage / transport, heat storage / transport, heat-mechanical energy conversion, hydrogen separation / purification, hydrogen isotope separation, batteries using hydrogen as an active material, The catalysts, temperature sensors, etc. in synthetic chemistry are further expanded, and further remarkable effects can be achieved, such as the development of new fields for utilizing hydrogen storage alloys.

Further, the hydrogen storage alloy and the surface modification method thereof according to the present invention can be easily activated and the hydrogen storage characteristics can be improved. A large capacity is achieved in an alkaline storage battery including such a hydrogen storage alloy as a negative electrode and the negative electrode.

Further, the battery negative electrode and the alkaline storage battery according to the present invention stabilize the charge / discharge reaction for a long period of time by enabling the application of the magnesium-containing hydrogen storage alloy, which has been conventionally difficult, to the charge / discharge reaction. It is possible to obtain a remarkable effect such as having a high capacity.

[Brief description of drawings]

FIG. 1 is a state diagram of a Mg—Ni alloy.

FIG. 2 is a state diagram of a La—Ni based alloy.

FIG. 3 is a partially cutaway perspective view showing a cylindrical alkaline storage battery according to the present invention.

FIG. 4 is a characteristic diagram showing the relationship between _y of Mg ₂ Ni _y and the amount of eluted magnesium.

FIG. 5 is a diagram for explaining measurement of maximum stress of strip-shaped alloy pieces.

FIG. 6 is a schematic diagram showing a temperature scanning type hydrogen storage / release characteristic evaluation device used in an example of the present invention.

FIG. 7 is a characteristic diagram showing a pressure change (temperature decrease due to hydrogen storage of the hydrogen storage alloys) with temperature rise of the hydrogen storage alloys of Examples 16 and 17 and Comparative Examples 3 and 11.

FIG. 8 is a characteristic diagram showing a pressure change (temperature decrease due to hydrogen storage of the hydrogen storage alloy) with a temperature rise of the hydrogen storage alloys of Example 18 and Comparative Example 3.

FIG. 9 is a characteristic diagram showing pressure changes during hydrogen storage at 25 ° C. in a Mg ₂ Ni hydrogen storage alloy before and after surface modification.

10 is a characteristic diagram showing the relationship between the number of cycles and the discharge capacity of the simulated cell provided with the negative electrode in Example 94 and Comparative Example 15. FIG.

[Explanation of symbols]

1 ... Container, 2 ... Positive electrode, 4 ... Negative electrode, 5 ... Electrode group, 7 ... Seal plate, 31 ... Hydrogen cylinder, 33 ... Sample container, 35 ... Vacuum pump, 36 ... Pressure gauge, 39 ... Heater, 41 ... Computer, 42 ... Temperature controller.

Claims (15)

[Claims] 1. A hydrogen storage alloy comprising an alloy represented by the following general formula (I): Mg ₂ M 1 _y (I) However, M 1 is at least one element selected from Mg, an element capable of reacting exothermically with hydrogen, an element other than Al and B, and not reacting exothermically with hydrogen. , Y
Is defined as 1 <y ≦ 1.5. 2. A hydrogen storage alloy comprising an alloy represented by the following general formula (II). Mg _2-x M2 _x M1 _y (II) where M2 is an element that can react exothermically with hydrogen, Al
And at least one element other than Mg selected from B, M1 is at least one element selected from the elements other than Mg and M2 and which does not react exothermically with hydrogen, and x is 0 <x ≦ 1.0. , Y is defined as 1 <y ≦ 2.5. 3. A hydrogen storage alloy comprising an alloy represented by the following general formula (III): M _2-x M2 _x M1 _y (III) where M is Be, Ca, Sr, Ba, Y, Ra, L
a, Ce, Pr, Pm, Sm, Eu, Gd, Tb, D
y, Ho, Er, Tm, Tb, Lu, Ti, Zr, H
at least one element selected from f, Pd, and Pt, M
2 is an element capable of reacting exothermically with hydrogen, at least one element other than M selected from Al and B, M1 is an element other than M and M2, and is at least selected from an element which does not react exothermically with hydrogen One element, x and y, is defined as 0.01 <x ≦ 1.0 and 0.5 <y ≦ 1.5, respectively. 4. A hydrogen storage alloy is used as an RX compound (provided that R
Is an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a substitution product thereof, and X is a halogen element). 5. A half-value width Δ (2θ) of at least one of the peaks of the three strong lines in a peak obtained by X-ray diffraction using CuKα as a radiation source is 0.3 ° ≦ Δ.
(2θ) ≦ 10 °, a hydrogen storage alloy. 6. An alloy containing 10% or more of magnesium,
20 ° at the X-ray diffraction peak with CuKα as the radiation source
The apparent half width Δ (2θ ₁ ) at the peak in the vicinity is 0.3 ° ≦ Δ (2θ ₁ ) ≦ 10 °, or 40
The apparent full width at half maximum Δ (2θ ₂ ) at the peak near 0 ° is 0.
A hydrogen storage alloy, wherein 3 ° ≦ Δ (2θ ₂ ) ≦ 10 °. 7. A method for surface modification of a hydrogen storage alloy, which comprises subjecting the hydrogen storage alloy to mechanical treatment in a vacuum, an atmosphere of an inert gas or hydrogen. 8. A negative electrode for a battery containing a hydrogen storage alloy represented by the following general formula (I). Mg ₂ M 1 _y (I) However, M 1 is at least one element selected from Mg, an element capable of reacting exothermically with hydrogen, an element other than Al and B, and not reacting exothermically with hydrogen. , Y
Is defined as 1 <y ≦ 1.5. 9. An alkaline secondary battery comprising a negative electrode containing a hydrogen storage alloy represented by the following general formula (I). Mg ₂ M 1 _y (I) However, M 1 is at least one element selected from Mg, an element capable of reacting exothermically with hydrogen, an element other than Al and B, and not reacting exothermically with hydrogen. , Y
Is defined as 1 <y ≦ 1.5. 10. A negative electrode for a battery containing a hydrogen storage alloy represented by the following general formula (II). Mg _2-x M2 _x M1 _y (II) where M2 is an element that can react exothermically with hydrogen, Al
And at least one element other than Mg selected from B, M1 is at least one element selected from the elements other than Mg and M2 and which does not react exothermically with hydrogen, and x is 0 <x ≦ 1.0. , Y is defined as 1 <y ≦ 2.5. 11. An alkaline secondary battery comprising a negative electrode containing a hydrogen storage alloy represented by the following general formula (II). Mg _2-x M2 _x M1 _y (II) where M2 is an element that can react exothermically with hydrogen, Al
And at least one element other than Mg selected from B, M1 is at least one element selected from the elements other than Mg and M2 and which does not react exothermically with hydrogen, and x is 0 <x ≦ 1.0. , Y is defined as 1 <y ≦ 2.5. 12. A peak obtained by X-ray diffraction using CuKα as a radiation source has a half-value width Δ (2θ) of 0.3 ° ≦ at least one of the three strong line peaks.
A negative electrode for a battery, comprising a hydrogen storage alloy having Δ (2θ) ≦ 10 °. 13. Among the peaks obtained by X-ray diffraction using CuKα as a radiation source, at least one of the peaks of the three strong lines has a half value width Δ (2θ) of 0.3 ° ≦.
An alkaline secondary battery comprising a negative electrode containing a hydrogen storage alloy with Δ (2θ) ≦ 10 °. 14. A negative electrode containing a hydrogen storage alloy containing magnesium, which is (a) when immersed in an aqueous solution of an alkali hydroxide having a normality of 6 to 8: (a) elution of magnesium ions into the aqueous solution of alkali hydroxide at room temperature. Speed is 0.5 mg / kg
Alloy / hr or less, or the elution rate of magnesium ions into an alkali hydroxide aqueous solution at 60 ° C is 4 mg / kg alloy /
Either less than or equal to hr, and (b) the elution rate of the alloying elements in the aqueous alkali hydroxide solution at room temperature is 1.5 m.
A negative electrode for a battery, characterized in that the elution rate of alloying component elements into an aqueous solution of alkali hydroxide at 60 ° C. is 20 mg / kg alloy / hr or less. 15. A negative electrode containing a hydrogen storage alloy containing magnesium, which is housed in a container, and a positive electrode, which is housed in the container and has a separator sandwiched between the negative electrodes.
An alkaline secondary battery comprising an alkaline electrolyte contained in the container, wherein the alkaline electrolyte is injected into the container and the container is sealed, and then at a time point of 30 days or more has elapsed. An alkaline secondary battery having a magnesium ion concentration of 2.2 mg / liter or less in an alkaline electrolyte.