JPH10259445A - Hydrogen storage alloy, its production and nickel-hydrogen secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hydrogen storage alloy excellent in hydrogen occluding characteristics and corrosion resistance and useful as the material for the negative electrode of a battery by preparing a hydrogen storage alloy shown by a specified formula in which elements selected from each group of La, Ce or the like, of Ti, Zr or the like and of Co, Ni or the like are contained in specified ratios and fine crystal phases are precipitated. SOLUTION: A hydrogen storage alloy composed of an alloy expressed by the general formula of (Ra M1-a )100-6 T6 [where R denotes one or more kinds of elements among La, Ce, Nd, Sm, and Y, M denotes one or more kinds of elements among Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W, T denotes one or more kinds of elements among Mn, Fe, Co, Ni, Cu, Zn, B, Al, Si and Sn, (a) satisfies 0<a<1 by atomic ratio, and (b) satisfies 30<=b<=80 by atomic %], and in which fine crystal phases having <= 10 μm grain size are precipitated into at least a part of the alloy structure is prepd. In the case this hydrogen storage alloy is used as the active substance of the negative electrode of a secondary battery, high electrode capacitance, long life characteristics so as to withstand repeated use and high dischargeability are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen storage alloy, a method for producing the same, and a nickel-hydrogen secondary battery using the alloy, and more particularly, to a case where the alloy is used as an active material for a negative electrode of a secondary battery. Hydrogen storage alloy capable of satisfying both high electrode capacity (battery capacity), long life characteristics (long cycle characteristics) that can withstand repeated use, and high rate discharge performance,
The present invention relates to a method for manufacturing the same and a nickel-metal hydride secondary battery.

[0002]

2. Description of the Related Art Unlike conventional fossil fuels such as petroleum-based fuels, hydrogen, which is converted into H ₂ O without generating harmful gases even when burned, has attracted attention as a clean energy source.
In order to realize this specific use of hydrogen, a method of storing and transporting hydrogen on a practical scale is important. However, when hydrogen is stored as a gas in a normal cylinder, the volume of the cylinder becomes excessive.On the other hand, when hydrogen is stored at a very low temperature as a liquid, auxiliary equipment such as a refrigeration facility is required. Anyway, there is a problem that the storage equipment becomes large. Therefore, a hydrogen storage alloy that absorbs hydrogen as a metal oxide by reacting with hydrogen and releases hydrogen by heating or the like has attracted attention as a means for storing and transporting hydrogen.
The application range of hydrogen storage alloys is wide, and in addition to the above-mentioned hydrogen storage means and transport means, fuel sources for hydrogen-powered vehicles, negative electrode materials for secondary batteries, hydrogen separation / recovery / purification equipment, heat pumps, cooling / heating systems, refrigeration Applications in various fields such as systems, heat storage devices, actuators, compressors, temperature sensors, and catalysts are being studied. In particular, applications of the hydrogen storage alloy as a negative electrode material of a secondary battery are steadily expanding.

In other words, recent advances in electronic technology have led to power savings, and advances in packaging technology have led to smaller and more portable electronic devices that could not be expected in the past. Accordingly, there is a particular demand for a secondary battery as a power source of the electronic device to have a high capacity, a long life, and a stable discharge current. For example, in OA devices, telephones, and AV devices that are becoming more personalized and portable, there is a demand for the development of a high-performance battery, particularly for the purpose of reducing the size and weight and extending the use time of the device cordlessly. As a battery corresponding to such a demand, a non-sintered Ni-Cd secondary battery having a three-dimensional structure using an electrode substrate of a conventional sintered nickel cadmium (Ni-Cd) battery has been developed. No significant capacity increase has been achieved.

Therefore, in recent years, an alkaline secondary battery (nickel-metal hydride secondary battery) using a structure in which a hydrogen storage alloy powder is fixed to a current collector as a negative electrode has been proposed and attracted attention. The negative electrode used in this nickel-metal hydride battery is
Generally, it is manufactured by the following procedure. That is, after the hydrogen storage alloy is melted by a high-frequency melting method or an arc melting method, the mixture is cooled and pulverized, and a conductive agent and a binder are added to the obtained pulverized powder to form a kneaded material, and the kneaded material is collected. It is manufactured by coating or crimping on an electric body. A negative electrode using this hydrogen storage alloy can increase the effective energy density per unit weight or unit volume as compared with cadmium (Cd), which is a conventional representative negative electrode material for alkaline secondary batteries. In addition to being able to increase the capacity of the battery, it has the characteristics of being less toxic and less likely to cause environmental pollution.

[0005] However, the negative electrode containing the hydrogen storage alloy is immersed in a concentrated alkaline aqueous solution as an electrolytic solution in a state where the negative electrode is incorporated in a secondary battery, and is exposed to oxygen generated from the positive electrode particularly during overcharge. In addition, the hydrogen storage alloy is corroded and the electrode characteristics are likely to deteriorate. Further, at the time of charging and discharging, the volume expands and contracts in accordance with the occlusion and release of hydrogen in the hydrogen storage alloy, so that the hydrogen storage alloy cracks and the hydrogen storage alloy powder becomes finer. As the pulverization of the hydrogen storage alloy progresses, the specific surface area of the hydrogen storage alloy increases at an accelerated rate, so that the ratio of the area of the surface of the hydrogen storage alloy deteriorated by the alkaline electrolyte increases. Moreover, since the conductivity between the hydrogen storage alloy powder and the current collector also deteriorates,
The cycle life is reduced and the electrode characteristics are also deteriorated.

Therefore, in order to solve the above-mentioned problem, the hydrogen storage alloy is diversified, or a nickel thin film or a copper thin film is adhered to the surface of the hydrogen storage alloy powder or the negative electrode including the hydrogen storage alloy by plating, vapor deposition, or the like. Improve corrosion resistance by preventing direct contact with the electrolyte, prevent mechanical cracks by increasing mechanical strength, or suppress deterioration of the hydrogen storage alloy surface by immersing it in an alkaline solution and drying it. However, it has not always been possible to achieve a sufficient improvement, and in some cases, the electrode capacity is reduced.

[0007] As the hydrogen storage alloy used for the alkaline secondary battery, there is AB ₅ type alloy represented by LaNi _5. The negative electrode using the alloy system having the hexagonal structure has a more effective battery per unit weight or unit volume than the case of using cadmium which is a conventional representative negative electrode material for an alkaline secondary battery. Energy density can be increased, the battery capacity can be increased, and there is little risk of environmental pollution such as cadmium pollution, and the battery characteristics are good. .
In the battery using the AB ₅ type alloy, there is a characteristic that can be discharged at a high current value, there is an advantage that it is possible to so-called high rate discharge.

[0008]

[SUMMARY OF THE INVENTION However, for example, the electrode capacitance of the Lm-Ni-Co-Al alloy (Lm is La enriched misch metal) conventional AB ₅ type hydrogen-absorbing alloy comprising the current 300 mAh / g It was slightly exceeded, and the cycle life due to charge and discharge was not sufficient in a situation where higher capacity and longer life of the battery were desired.

On the other hand, in a battery using a so-called AB ₂ -based hydrogen storage alloy as a negative electrode material, which is made of a composition material such as ZrNi ₂ or ZrMn _2, a capacity of 400 mAh / g or more can be obtained, but a high-rate discharge Then, there is a problem that the battery function is remarkably reduced, such as a sudden decrease in capacity and an insufficient life, and in any case, a problem that operation reliability of the device using the battery is greatly reduced. There was a point.

A hydrogen storage alloy made of an Mg ₂ Ni alloy has a property of storing a large amount of hydrogen, but it is extremely difficult to release hydrogen. Unless measures are taken to increase the battery capacity, a negative electrode of the battery is required. There was also a problem that practical use as a material was difficult.

In a conventional nickel-metal hydride battery using a hydrogen-absorbing alloy as a negative electrode material, the deterioration of the alloy is apt to proceed rapidly when held at a high temperature condition when not in use. There is also a problem that characteristics are deteriorated.

Further, the temperature range in which the battery is used (−2)
(0 ° C. to + 80 ° C.) in the upper limit temperature range and the lower limit temperature range, the battery capacity is remarkably reduced, and in some cases, the battery does not discharge. was there. In particular, when used in a cold region, the voltage drop becomes large, and there is a problem that the device malfunctions. In any case, the operation reliability of the device using a battery as a driving power source is greatly reduced. was there.

Further, there has been a problem that the capacity rising characteristics (easiness of activation) of the battery become poor. That is, there is a problem that a predetermined high electrode capacity cannot be obtained immediately by only a small number of activation operations (charge / discharge operations) after the battery is assembled. This capacity rising property is a characteristic that does not need to be noticed when a user uses a battery as a product. However, if the capacity rising property is poor, the number of man-hours for manufacturing the battery increases, and the manufacturing cost of the battery increases significantly. This is one of the important characteristics when battery design is performed on the manufacturer side.

The present invention has been made in order to solve the above problems, and when used as a negative electrode material for a battery, both high electrode capacity, long life characteristics that can withstand repeated use, and high rate discharge characteristics are satisfied. It is an object of the present invention to provide a hydrogen storage alloy which can be used, a method for producing the same, and a nickel-metal hydride secondary battery using the alloy.

[0015]

In order to achieve the above object, the present inventors have prepared alloys having various metal structures, crystal structures and compositions, and the structures, crystal grain sizes and compositions of the alloys are determined by the capacity of the battery. And their effects on start-up, life characteristics, temperature dependence and high-rate discharge were compared. As a result, the alloying elements are considered to be difficult, and the combination of the elements forming the hydride is added to each element group and the element that is easy to alloy to obtain an alloy raw material having a predetermined composition, The molten metal having this predetermined composition is rapidly solidified, or mechanical processing such as mechanical alloying or mechanical grinding is performed on the alloy raw material,
Once an alloy material having a specific non-equilibrium phase is prepared, and then the alloy material is heat-treated to prepare an alloy in which a fine crystal phase is precipitated, the hydrogen absorption characteristics and corrosion resistance are excellent. An alloy is obtained, and when this alloy is used as a negative electrode material for a secondary battery, nickel is excellent in battery characteristics such as electrode capacity, life characteristics, high temperature resistance, temperature dependency, capacity rising property and high rate discharge property. The knowledge that a hydrogen secondary battery can be obtained was obtained. The present invention has been completed based on the above findings.

That is, the hydrogen storage alloy according to the present invention has the general formula (R _a M _1-a ) _100-b T _b (where R is La, C
e, at least one element selected from Pr, Nd, Sm and Y, and M is Ti, Zr, Hf, V, N
b, Ta, Cr, Mo and W are at least one element selected from the group consisting of Mn, Fe, Co, Ni, C
It is at least one element selected from u, Zn, B, Al, Si and Sn, a is an atomic ratio of 0 <a <1, and b is an atomic% and 30 ≦ b ≦ 80. ), Wherein a fine crystal phase having a crystal grain size of 10 μm or less is precipitated in at least a part of the alloy structure. The average crystal grain size of the alloy is preferably in the range of 1 nm to 5 μm.

Further, when the atomic ratio a of the R component such as a rare earth element contained in the alloy is in the range of 0 <a ≦ 0.3, the life characteristics (high-temperature resistance) particularly under high-temperature storage conditions
, A nickel-hydrogen secondary battery having a good value can be obtained. Further, when the atomic ratio a of the R component contained in the alloy is in the range of 0.3 <a ≦ 0.7, a nickel-hydrogen secondary battery having particularly low temperature dependence and good temperature characteristics can be obtained. . Further, when the atomic ratio a of the R component contained in the alloy is in the range of 0.7 <a <1, a nickel-metal hydride secondary battery having particularly good capacity rising characteristics can be obtained.

Further, in the method for producing a hydrogen storage alloy according to the present invention, an alloy having the above-mentioned predetermined composition and having a non-equilibrium phase formed in at least a part of the alloy structure is prepared, and then the obtained alloy is heat-treated. As a result, the average grain size is 1 nm to 5 nm.
It is characterized in that a fine crystal phase of μm is precipitated.

Further, in the nickel-hydrogen secondary battery according to the present invention, an electrically insulating separator is interposed between a negative electrode containing a hydrogen storage alloy having the above-mentioned predetermined composition and crystal structure and a positive electrode containing nickel oxide. The sealed container is housed in a closed container, and the closed container is filled with an alkaline electrolyte.

In the hydrogen storage alloy according to the present invention, the R component in the general formula is La, Ce, Pr, Nd, Sm and Y.
At least one element selected from the group consisting of: When each of the elements relating to the R component is contained together with the M component, the alloy is uniformly dispersed in the alloy structure by an alloying technique such as a molten metal quenching process or a mechanical alloying process, and has a function of promoting the refinement of crystal grains. Have.

The M component is a group IVa, Va, or VIa element, that is, Ti, Zr, Hf, V, Nb, Ta, C
at least one element selected from the group consisting of r, Mo, and W, each of which is a basic element that contributes to the hydrogen storage capacity of the alloy, and desorbs hydrogen in consideration of the content of other elements, particularly, the T component described later. It is an element that facilitates storage.

The refinement of the crystal grains is effective in facilitating the initial activation of the battery and promoting the absorption and desorption of hydrogen. Here, when the average crystal grain size of the alloy is less than 1 nm or more than 5 μm, the above-mentioned initial activity is increased, and the effect of promoting hydrogen absorption and desorption is reduced. Therefore, the average crystal grain size of the alloy is set to 10 μm or less, and further 1 nm.
The range of not less than 5 to 5 μm is more preferable.

The content of the R component is in the range of 0 <a <1 in terms of the atomic ratio a to the total amount with the M component. But,
When the content of the R component is less than 0.01 in atomic ratio a, the refinement of the alloy structure is not promoted, while when the content exceeds 0.3, the battery when kept in a high-temperature environment at regular time intervals is used. Starts to deteriorate. Therefore, in order to form a battery having particularly excellent high temperature resistance, the content of the R component is set to 0.0
It is preferred to be in the range of 1 to 0.3.

When the content of the R component is more than 0.3 and 0.7 or less in atomic ratio, the temperature dependency is particularly low,
While a battery having good temperature characteristics can be obtained, the rise due to the cycle of the discharge capacity tends to be slow. Further, when the R component content is more than 0.7 and less than 1, a battery having a good capacity rising characteristic can be obtained. The alloy of the present invention preferably has a multi-phase structure having an alloy phase such as MT or RT as a main phase from the viewpoint of improving battery characteristics.

The T component is Mn, Fe, Ni, Co,
It is at least one element selected from Cu, Zn, B, Al, Si and Sn, and all of these elements enhance the diffusion of hydrogen penetrating into the alloy and the catalytic action on the alloy surface, and also increase the activity of the alloy. It is an element that improves the corrosion resistance and suppresses the cracking of the alloy due to the expansion of the lattice at the time of hydrogen absorption, thereby exerting the effect of improving the life. These T
When the added amount b of the component is less than 30 atomic%, the hydrogen release is not sufficient, and the above-mentioned improvement effect is insufficient. On the other hand, when the added amount b exceeds 80 atomic%, the capacity becomes remarkable. Therefore, the addition amount b of the T component is set in the range of 30 to 80 atomic%, but more preferably in the range of 40 to 70 atomic%. In order to enhance the catalytic action on the alloy surface, Ni is particularly preferable among the above T components. Further, Co is particularly preferable as an element that suppresses cracks caused by lattice expansion during hydrogen storage and improves the life characteristics.

Further, among the above alloy components, particularly Ni is M
It is an element that is effective in forming and absorbing hydrogen by forming a hydrogen storage alloy having excellent corrosion resistance by being alloyed with the components. In addition, elements such as Co, Fe, and Cu are elements that improve the corrosion resistance of the alloy, effectively suppress the generation of cracks due to the expansion of the lattice during hydrogen absorption, and exhibit a life improving effect. Elements such as Mn, Al, and Si are all elements that contribute to improving the life of the alloy.
Furthermore, elements such as Si, Cr, and Sn are all effective in improving the life of the alloy.

Of the above-mentioned T components, Mn is effective in increasing the capacity of the negative electrode containing the hydrogen storage alloy, improving the corrosion resistance by accelerating the formation of the passive film, and adjusting the decrease in the hydrogen storage / release pressure (equilibrium pressure). is there. On the other hand, Al has the effect of lowering the storage / release pressure (dissociation pressure) of hydrogen to the operating pressure suitable for a sealed battery, as well as Mn, and can increase the durability.

Further, Co as the T component is effective in improving the corrosion resistance of the alloy against an electrolytic solution or the like, and the pulverization of the alloy is remarkably suppressed, and the life characteristics of the battery are improved. When the amount of Co added is increased, the cycle life is improved, but the electrode capacity tends to decrease. Therefore, it is necessary to optimize the amount of Co added according to the use of the battery.

In addition, the hydrogen storage alloy according to the present invention includes:
Elements such as C, N, O, F, and Cl may be contained as impurities as long as the properties of the alloy of the present invention are not impaired. The content of these impurities was 6000 each.
It is preferably in the range of ppm or less. More preferably 5,000 ppm or less, still more preferably 4000 pp
m or less is good.

As a method for producing a hydrogen storage alloy according to the present invention, a raw material mixture prepared so as to have a predetermined composition is heated in a high-frequency induction furnace to prepare a molten alloy. Injected onto a cooling body moving at a high speed, quenched and solidified at a cooling rate of 100 ° C./sec or more to prepare a quenched alloy having a non-equilibrium phase formed at least in part, and then heat-treating the obtained quenched alloy By doing so, it can be produced by precipitating a fine crystal phase having an average particle size of 1 nm to 5 μm. By the rapid solidification treatment, it is possible to obtain a molten metal quenched alloy having a non-equilibrium phase in which the additional components are uniformly dispersed in the alloy structure. As a method of performing such rapid solidification treatment, there are a molten metal quenching method such as a gas atomizing method, a rotating disk method, a centrifugal spraying method, a single roll method and a twin roll method.

When cooling the molten alloy, the cooling rate is 100 ° C./sec or more, preferably 300 ° C./sec or more.
More preferably, by setting the temperature to 1800 ° C./second or more, even when a rare earth element such as La or an element that easily segregates is contained in a relatively large amount, the structure is uniform.
An alloy with less segregation can be obtained.

As a specific method of cooling and solidifying the molten alloy, for example, the molten alloy is injected onto a high-speed moving cooling body,
There is a method of obtaining a flake-like sample having a thickness of about 10 to 100 μm. The obtained sample is an MT made of fine crystals.
Phase, the RT phase, etc. are the main phases, and the average crystal grain size is 1
It is about mm to 5 μm.

As a method for cooling and solidifying the molten alloy, a quenching method for rapidly cooling the molten alloy in a molten state such as a gas atomizing method, a rotating disk method, a centrifugal spraying method, a single roll method, a twin roll method, etc. is used. The material and surface properties of the cooling roll, the number of revolutions of the cooling roll (peripheral speed of the running surface), the temperature of the molten metal, the temperature of the cooling water for the cooling roll, the gas type in the cooling chamber, the pressure, the diameter of the molten metal injection nozzle, the injection amount By optimizing the manufacturing conditions, the alloy can be manufactured stably in large quantities.

Single Roll Method FIG. 1 shows an apparatus for producing a hydrogen storage alloy by a single roll method. This manufacturing apparatus stores a cooling roll 5 having a diameter of about 400 mm, which is excellent in heat conductivity such as copper and nickel, and a hydrogen storage alloy melt 3 supplied from a ladle 2 and then sprays the same onto the running surface of the cooling roll 5. And a pouring nozzle 4 to be used. The cooling roll 5 and the like are housed in a cooling chamber 1 adjusted to an inert gas atmosphere. The rotation speed of the cooling roll 5 depends on the wettability and the cooling speed of the cooling roll 5 and the injection amount of the hydrogen storage alloy melt 3, but is generally set to 100 to 5000 rpm.

In the manufacturing apparatus shown in FIG. 1, the molten hydrogen storage alloy 3 supplied from the ladle 2
When the molten alloy is further sprayed onto the running surface of the cooling roll 5, the alloy melt solidifies from the surface in contact with the cooling roll 5, and crystal growth starts,
The solidification is completely completed before the solidification is removed from the cooling roll 5. Thereafter, the cooling proceeds further while flying in the cooling chamber 1, and the hydrogen storage alloy 6 with less segregation and a uniform crystal growth direction is manufactured.

The twin roll method Figure 2 is a hydrogen storage alloy manufacturing apparatus according twin roll method. This manufacturing apparatus includes one or more pairs of cooling rolls 5 a, which are arranged in the cooling chamber 1 such that respective running surfaces face each other.
5b, a melting furnace 7 for melting the raw material metal to prepare a hydrogen storage alloy melt 3, and a hydrogen storage alloy melt 3 from the melting furnace 7.
Is provided between the cooling rolls 5a and 5b via a tundish 8.

The cooling rolls 5a and 5b are formed of a material having excellent heat conductivity such as copper and iron and have a diameter of about 300 mm. The cooling rolls 5a and 5b are 0 to 0.5
100 to 200 while maintaining a small gap d of about mm.
It rotates at a high speed of about 0 rpm. In addition, as a cooling roll, as shown in FIG. 2, the running surface is parallel, and the running surface has a U-shaped or V-shaped cross-sectional shape.
A so-called mold roll can also be employed. Further, if the gap d between the cooling rolls 5a and 5b is excessively large, a cooling direction is not uniform, and as a result, a hydrogen storage alloy in which the crystal growth direction is not uniform is manufactured.

In the manufacturing apparatus shown in FIG. 2, the molten hydrogen storage alloy 3 is poured from the pouring nozzle 4 into the cooling rolls 5a,
When the molten hydrogen storage alloy is injected in the gap direction of 5b, solidification and crystal growth of the hydrogen storage alloy melt start from the sides in contact with the cooling rolls 5a, 5b on both sides, and complete solidification by the time the metal is separated from the cooling rolls 5a, 5b. Thereafter, the cooling proceeds further while flying in the cooling chamber 1, and the hydrogen storage alloy 6 with less segregation and a uniform crystal growth direction is manufactured.

When a ribbon-shaped, flake-shaped or granular hydrogen-absorbing alloy is produced by using the cooling and solidifying method as described above, the temperature gradient in the sample during the solidification cooling of the molten alloy, the material of the cooling roll and the rotating disk Depending on conditions such as the supply amount of the molten alloy, a non-equilibrium structure such as an amorphous phase, or a crystal structure including a non-equilibrium phase as a main phase and partially including fine crystal grains is formed in the alloy.

That is, in the production process of the alloy particles, 100 ° C./sec or more, preferably 300 ° C./sec or more,
More preferably, when the molten metal is quenched at a cooling rate of 1800 ° C./sec or more to produce a hydrogen storage alloy, the alloy structure is formed of only an amorphous phase or a non-equilibrium phase as a main phase and 1 nm to An alloy structure having fine crystal grains of about 5 μm is obtained.

Also, by using a mechanical processing method such as a mechanical alloying method or a mechanical grinding method instead of the molten metal quenching method, it is possible to produce alloy particles composed of fine crystal grains. is there. In other words, a planetary ball mill, which mechanically promotes the reaction between particles while applying a certain degree of impact force to the sample particles, and controls the metal structure of a sample prepared or alloyed in advance to have a predetermined composition, etc. May be used to produce alloy particles. In this mechanical processing method,
The processing time is about 1 to 100 hours, and the processing is preferably performed in an inert gas atmosphere such as argon or nitrogen gas or a reducing atmosphere such as hydrogen gas. The material of the ball mill pot or ball used is not particularly limited, but stainless steel and ceramics are preferred. The particle size of the alloy powder obtained by this mechanical treatment is preferably in the range of 0.1 to 100 μm.

In the alloy prepared by the molten metal quenching method or the mechanical treatment method as described above, internal strain and segregation are liable to occur, and in any case, when the alloy is used as a negative electrode material, the electrode capacity and life are reduced. Often do. Further, since a plateau region in the hydrogen storage capacity-pressure diagram is not formed in a non-equilibrium phase such as an amorphous phase formed in the alloy, when an alloy containing a large amount of the non-equilibrium phase is used as a battery material, The operating pressure during the occlusion and release reaction becomes unstable.

The alloy prepared therefrom was used at a temperature of 300 to 11
It is necessary to perform a heat treatment of heating at 00 ° C. for 10 minutes to 10 hours. By this heat treatment, a fine crystal phase is precipitated in the previously formed non-equilibrium phase, and at the same time, internal strain is removed and a homogeneous alloy structure is obtained. Further, since a plateau region is clearly formed in the crystallized metal phase, the operating pressure of a battery using this alloy can be stabilized.

When the temperature of the heat treatment is lower than 300 ° C., the crystallization of the non-equilibrium phase becomes insufficient, and it becomes difficult to remove the internal strain. When the temperature exceeds 1100 ° C., the composition changes due to oxidation and evaporation of the group IVa element and the rare earth element. Therefore, the heat treatment temperature is 3
The temperature is set in the range of 00 to 1100 ° C. In particular, in order to improve the electrode characteristics, the range of 450 to 900 ° C. is preferable.

If the heat treatment time is less than 10 minutes, the crystallization becomes non-uniform and the characteristics vary greatly. on the other hand,
If the treatment time is prolonged to more than 10 hours, the oxidation of the alloy surface is apt to progress, and the alloy composition is significantly shifted, which is not preferable. Therefore, in consideration of the production efficiency, 10 minutes to 10 hours is preferable.

The heat treatment atmosphere is preferably an inert gas atmosphere such as Ar or a vacuum in order to prevent high-temperature oxidation of the hydrogen storage alloy.

It is preferable to adjust the average particle size of the crystals precipitated in the alloy structure by the above heat treatment in the range of 1 nm to 5 μm from the viewpoint of improving battery characteristics. That is, if the average crystal grain size is too small, less than 1 nm, the hydrogen absorption characteristics of the alloy are insufficient, and the plateau region becomes unclear, which makes it particularly difficult to apply as a battery material. On the other hand, when the average crystal grain size is too large to exceed 5 μm, the high-rate discharge ratio is reduced. Therefore, the average grain size of the crystal is 1 nm to 5 μm.
m, preferably in the range of 1 nm to 3 μm,
Furthermore, the range of 1 nm to 1 μm is more preferable.

When a non-equilibrium phase such as an amorphous phase is finely crystallized by heat treatment in this way, a large amount of grain boundary phases, which serve as a diffusion path of hydrogen during hydrogen absorption / desorption, are formed, and a high capacity and a high capacity are obtained. It is considered that a long-life alloy can be realized.

Further, by performing the following surface treatment on the hydrogen storage alloy prepared by the molten metal quenching method or the mechanical treatment method as described above, the electrode characteristics can be improved when used as an electrode material. Can be. That is, by performing a surface treatment such as an acid treatment, an alkali treatment, a fluoride treatment, and an electroless plating treatment, the activity and corrosion resistance of the alloy surface can be increased. Among the above surface treatments, an alkali treatment using a KOH solution or a NaOH solution is particularly effective. The alkali treatment temperature is preferably in the range of 45 ° C. to the boiling point of the alkaline solution, and the treatment time is 5 minutes.
It is preferable to set the range of minutes to 24 hours. These surface treatments may be performed in a state where the solidified solid remains rapidly quenched. Further, it may be carried out in a state after pulverization or during pulverization in an alkaline solution.

Next, a nickel-metal hydride secondary battery (cylindrical nickel-metal hydride secondary battery) according to the present invention using the above-mentioned hydrogen storage alloy as a negative electrode active material will be described with reference to FIG.

The nickel-hydrogen secondary battery according to the present invention, the positive electrode 1 including the negative electrode 11 and the nickel oxide containing the above general formula (R _a M _1-a) hydrogen storage alloy represented by the _100-b T _b
The container 13 is housed in a closed container 14 with an electrically insulating separator 13 interposed therebetween, and the closed container 14 is filled with an alkaline electrolyte.

That is, the hydrogen storage alloy electrode (negative electrode) 11 containing a hydrogen storage alloy is a non-sintered nickel electrode (positive electrode).
12 are wound spirally with a separator 13 interposed therebetween, and housed in a bottomed cylindrical container 14. The alkaline electrolyte is contained in the container 14. A circular sealing plate 16 having a hole 15 in the center is arranged at the upper opening of the container 14. The ring-shaped insulating gasket 17 is disposed between the peripheral edge of the sealing plate 16 and the inner surface of the upper opening of the container 14, and is sealed to the container 14 by caulking to reduce the diameter of the upper opening inward. Board 1
6 is hermetically fixed via the gasket 17.
One end of the positive electrode lead 18 is connected to the positive electrode 12, and the other end is connected to the lower surface of the sealing plate 16. The cap-shaped positive electrode terminal 19 is provided on the sealing plate 16 with the hole 15.
It is attached to cover. Rubber safety valve 20
Is disposed so as to close the hole 15 in a space surrounded by the sealing plate 16 and the positive electrode terminal 19. The insulating tube 21 is used to fix the positive electrode terminal 19 and the flange paper 22 placed on the upper end of the container 14.
It is attached near the upper end of.

As the hydrogen storage alloy electrode 11, a paste type and a non-paste type described below are used. (1) The paste-type hydrogen storage alloy electrode is prepared by mixing a hydrogen storage alloy powder obtained by pulverizing the above-mentioned hydrogen storage alloy, a polymer binder, and a conductive powder to be added as necessary. The paste is applied to a conductive substrate serving as a current collector, filled, dried, and then subjected to a roller press or the like. (2) The non-paste type hydrogen storage alloy electrode is obtained by stirring the above-mentioned hydrogen storage alloy powder, the polymer binder, and the conductive powder to be added as required, and spraying the mixed powder on the conductive substrate serving as a current collector. It is produced by applying a roller press or the like.

As a method for pulverizing the hydrogen storage alloy, for example, a mechanical pulverization method such as a ball mill, a pulperizer, or a jet mill, or a method in which high-pressure hydrogen is occluded / released and pulverized by volume expansion at that time, is employed. .

As the polymer binder, for example, sodium polyacrylate, polytetrafluoroethylene (PTF)
E), carboxymethylcellulose (CMC), polyvinyl alcohol (PVA) and the like. Such a polymer binder is preferably blended in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the hydrogen storage alloy. However, when preparing the non-paste type hydrogen storage alloy electrode of the above (2), the hydrogen storage alloy powder and the conductive powder to be added as required are formed into a three-dimensional shape (mesh shape) by fiberization by stirring. It is preferable to use immobilizable polytetrafluoroethylene (PTFE) as the polymer binder.

Examples of the conductive powder include carbon powder such as graphite powder and Ketjen black, and metal powder such as nickel, copper and cobalt. Such conductive powder can be used as the hydrogen storage alloy 10
It is preferable to add 0.1 to 5 parts by weight to 0 part by weight.

As the conductive substrate, for example, a two-dimensional substrate such as a punched metal, an expanded metal, or a wire mesh, or a three-dimensional substrate such as a foamed metal substrate, a mesh-like sintered fiber substrate, or a felt-plated substrate obtained by plating a metal on a nonwoven fabric. Can be mentioned. However, when producing the non-paste type hydrogen storage alloy electrode of the above (2), it is preferable to use a two-dimensional substrate as the conductive substrate since a mixture containing the hydrogen storage alloy powder is sprayed.

The non-sintered nickel electrode 12 combined with the hydrogen storage alloy electrode is made of, for example, nickel hydroxide and cobalt hydroxide (Co (O
H) ₂ ), carboxymethyl cellulose (CMC), a mixture with cobalt monoxide (CoO), metallic cobalt, etc.
A polyacrylic acid salt such as sodium polyacrylate is appropriately blended to form a paste, and this paste is used as a foam metal substrate,
It is prepared by filling a substrate having a three-dimensional structure such as a reticulated sintered fiber substrate or a felt-plated substrate obtained by plating a metal on a non-woven fabric, drying it, and then performing roller pressing or the like.

The polymer fiber non-woven fabric used for the separator 13 is, for example, nylon, polypropylene,
Examples thereof include simple polymer fibers such as polyethylene, and composite polymer fibers obtained by blending these polymer fibers.

As the alkaline electrolyte, for example, a potassium hydroxide solution having a concentration of 6N to 9N or a mixture of the potassium hydroxide solution with lithium hydroxide, sodium hydroxide or the like is used.

According to the hydrogen storage alloy having the above structure, the types and composition ratios of the various elements constituting the alloy are properly set, and a fine crystal phase having excellent hydrogen storage characteristics is formed in the alloy structure. Therefore, a hydrogen storage alloy having excellent hydrogen storage characteristics and corrosion resistance can be obtained. Therefore, when this alloy is used as a negative electrode material, the battery capacity is increased, and the pulverization of the alloy due to the alkali solution can be prevented from being deteriorated. A battery can be provided.

[0062]

Next, embodiments of the present invention will be described more specifically with reference to the following examples.

Examples 1 to 10 Various metal raw material powders were blended so as to have the alloy compositions shown in the left column of Table 1, and the raw material powders for Examples 9 to 10 were
Using a planetary ball mill equipped with a Si ₃ N ₄ pot and a ball, mechanical alloying (MA) treatment was performed in a hydrogen atmosphere for 40 hours to obtain powdery samples. Next, the obtained samples were subjected to heat treatment under the temperature and time conditions shown in Table 1 to achieve crystallization and homogenization of the alloy structure, and to prepare hydrogen storage alloys according to Examples 9 to 10, respectively. .

On the other hand, the raw material mixtures for Examples 1 to 8 were heated and melted in a vacuum furnace to prepare molten alloys (master alloys) for the respective examples.

Next, the obtained molten alloy was solidified by cooling in an Ar atmosphere according to the following processing conditions to prepare flake-shaped alloy samples.

That is, the molten alloys for Examples 1 to 8 were rapidly solidified by a single roll method as shown in FIG. 1 to prepare flake-shaped alloy samples. As the cooling roll, a Cu roll having a diameter of 400 mm was used, the gap between the pouring nozzle (injection nozzle) and the cooling roll was set to 10 mm, the injection temperature was set to the melting point of each alloy + 150 ° C, and the injection pressure was set to 0.5 kg / cm ² . The quenching operation was performed in an Ar atmosphere, and the roll peripheral speed was set at 25 m / sec.

Of the alloy samples thus obtained, each of the quenched alloy samples manufactured by the single roll method had a flake shape and a thickness of 50 to 100 μm. These flake-like alloy samples were subjected to a heat treatment according to the temperature and time conditions shown in Table 1 to achieve crystallization and homogenization of the alloy structure.

Comparative Examples 1 and 2 Raw material powders were mixed so as to satisfy the alloy composition shown in the left column of Table 1, and the obtained raw material mixture was heated and melted in a vacuum furnace to obtain an alloy melt for each comparative example. Each was prepared. Incidentally, the alloy composition according to Comparative Example 1 shows a typical composition of a conventional AB ₅ type hydrogen storage alloy, the alloy composition of Comparative Example 2, another exemplary conventional AB ₅ type hydrogen storage alloy An example of a suitable composition is shown below.

Then, each alloy melt was solidified by cooling at a cooling rate of 5 to 60 ° C./min by a casting method, and a block-shaped alloy sample (hydrogen storage alloy) according to Comparative Examples 1 and 2 each having a thickness of 50 mm was prepared. ) Was prepared. Further, the obtained alloy samples of Comparative Examples 1 and 2 were heated at 1000 ° C. for 5 hours to perform a heat treatment.

Next, each of the obtained flake-shaped alloy samples was coarsely pulverized, then finely pulverized by a hammer mill, and the obtained pulverized powder was passed through a sieve and classified to a particle size of 75 μm or less. This was a hydrogen storage alloy powder. The average particle size was 35 to 40 μm. Further, the hydrogen storage alloy powder for each battery was subjected to X-ray diffraction, and the average crystal grain size was calculated from the obtained half-width based on Scheerer's formula,
The results shown in Table 1 were obtained.

Next, in order to evaluate the characteristics of the hydrogen storage alloy for a battery according to each of the above Examples and Comparative Examples as a battery material, an electrode was prepared using each of the hydrogen storage alloys for a battery according to the following procedure. Was formed, and its electrode capacity, number of charge / discharge cycles (life), and high rate discharge were measured.

First, the hydrogen storage alloy powder for a battery, the PTFE powder, and the carbon powder according to the above Examples and Comparative Examples were adjusted to 95.5%, 4.0%, and 0.5% by weight, respectively. After weighing, each electrode sheet was prepared by kneading and rolling. The electrode sheet was cut out to a predetermined size, and pressed to a nickel current collector to prepare a hydrogen storage alloy electrode.

On the other hand, a small amount of CMC (carboxymethylcellulose) and water were added to 90% by weight of nickel hydroxide and 10% by weight of cobalt monoxide and mixed by stirring to prepare a paste. This paste was filled in a porous nickel body having a three-dimensional structure, dried, and then rolled by a roller press to produce a nickel electrode.

The capacity of each of the above-mentioned hydrogen storage alloy electrodes and the nickel electrode was combined and measured by the unipolar evaluation, while the life was evaluated by the nickel-metal hydride battery (4/3 -A size, 4000m
(Ah specification battery) was assembled and evaluated. Here, an 8N aqueous potassium hydroxide solution was used as the electrolytic solution.

In the evaluation of the capacity of each hydrogen storage alloy electrode, the battery was charged to 400 mAh / g at a current value of 200 mA per gram of alloy (200 mA / g) in a constant temperature bath at 40 ° C., and then the Hg / HgO was charged at the above current value. With respect to the reference electrode,
The battery was discharged until the potential reached 0.5 V, and the charge and discharge were repeated, and the value when the amount of discharge reached the maximum was measured as the capacity.

The high rate discharge property is determined by measuring the capacities at discharge currents per unit weight of 20 mA / g and 200 mA / g as C ₂₀ and C ₂₀₀ , respectively, and their ratio (C ₂₀₀ / C ₂₀ ). Was defined as a high rate discharge ratio, and the ratio was evaluated according to the magnitude of the ratio.

In the life evaluation, 4 A
After charging for 1.1 hours, until the battery voltage reaches 0.9 V
The charge / discharge cycle of discharging with the current of A is repeated, and the number of cycles until the battery capacity becomes 80% of the initial capacity is set to 40 ° C.
And measured as battery life. Table 1 below shows the measurement results.

[0078]

[Table 1]

As is clear from the results shown in Table 1 above,
After appropriately setting the types of the elements constituting the M component, the R component and the T component in the general formula and the composition ratio of each component, and solidifying by cooling, heat treatment is performed to precipitate a fine crystal phase. In the electrode and the battery formed using the hydrogen storage alloy according to each of the prepared examples, the electrode capacity, the life, and the high-rate discharge performance were compared with those of the comparative example having the conventional composition ratio and alloy structure. It was confirmed that all the characteristics were good and that excellent battery performance could be exhibited.

[0080] On the other hand, in the conventional AB ₅ type hydrogen storage alloy a is Comparative Example 1 Alloy although the high rate discharge properties are equivalent to Example, found that capacity and service life may be reduced as compared with Example did. Further, in another conventional AB ₅ type hydrogen storage alloy a is Comparative Example 2 alloy, but approximates to an embodiment for volume, that high-rate discharge properties and lifetime is greatly reduced has been confirmed. That is, it was found that by setting the composition range specified in the present example and forming a fine crystal phase, a nickel-hydrogen secondary battery having a high capacity, a long life, and an excellent high-rate discharge property can be obtained. did.

Next, the high-temperature resistance of the nickel-metal hydride secondary batteries using the respective hydrogen storage alloys was examined in Examples 1 to 4 described above.
In addition to the batteries of Example 9 and Comparative Examples 1 and 2, batteries using the hydrogen storage alloys of Example 11 and Comparative Example 3 below were prepared and evaluated.

Examples 11 to 16 and Comparative Example 3 Raw materials were blended so as to have the alloy compositions shown in Table 2, and the obtained raw material mixture was heated and melted in a vacuum furnace to obtain Examples 11 to 16 .
The alloy melts for No. 16 and Comparative Example 3 were respectively prepared. Each alloy melt was quenched by the single roll method in the same manner as in Example 9, and further heat-treated at the temperature and time conditions shown in Table 2.
The average crystal grain size of each alloy powder obtained by further classification was measured, and the results shown in Table 2 were obtained.

Also, using the hydrogen storage alloy powders according to Examples 11 to 16 and Comparative Example 3,
A / 3-A size battery was prepared and its capacity and life were measured. The life evaluation conditions were the same as those in Example 9 except that a condition that the battery was left at a temperature of 90 ° C. for one day every 30 charge / discharge cycles was added. The life measured by this method is shown in Table 2 below as a high-temperature storage life. The batteries of Comparative Examples 1 and 2 were similarly measured, and the results shown in Table 2 below were obtained.

[0084]

[Table 2]

As is clear from the results shown in Table 2 above,
According to the battery according to the embodiment, the high-temperature exposure lifetime becomes higher than the battery of Comparative Example 1-2 using the conventional AB ₅ type hydrogen storage alloys, when used under severe high temperature conditions It was confirmed that excellent life characteristics were exhibited also in

In particular, in the batteries of Examples 1 to 5 in which the atomic ratio a of the R component is 0.05 to 0.25 with respect to the sum of the content of the R component and the amount of the M component, the high temperature storage life is particularly prolonged. It was found to have excellent high temperature resistance. On the other hand, R
In the battery of Comparative Example 3 containing no component and the battery of Example 16 having a relatively large content of the R component, it was found that while the capacity was secured, the lifetime at high temperature was shortened.

Next, the characteristics of a battery using a hydrogen storage alloy in which the atomic ratio a of the R component to the total amount of the R component and the M component is in the range of 0.3 to 0.7 will be described based on the following examples. explain.

Examples 17 to 26 Various raw material powders were blended so as to have the alloy compositions shown in the left column of Table 3, and the raw material powders for Examples 25 to 26 were mechanically treated in a hydrogen atmosphere in the same manner as in Example 1. Alloying (M
A) Processing was performed to obtain powdery alloy samples.

On the other hand, the raw material powders for Examples 17 to 24 were heated and melted in a vacuum furnace to prepare molten alloys (master alloys), and each molten alloy was prepared by the single roll method under the same conditions as in Example 9. A flake-like alloy sample was obtained.

Next, each alloy sample was heat-treated under the conditions shown in Table 3 and then classified to obtain the hydrogen storage alloy powder according to each Example. Similarly, the average crystal grain size was measured to obtain the results shown in Table 3. .

Further, a 4000 mAh secondary battery of 4/3 A size was prepared using the hydrogen storage alloy powder of each embodiment, and the capacity, life and high rate discharge ratio were measured under the same conditions as in the first embodiment. The results shown in Table 3 below were obtained. The measurement results for the batteries according to Comparative Examples 1 and 2 are also shown.

[0092]

[Table 3]

As is clear from the results shown in Table 3 above,
Having a predetermined composition, in the nickel-hydrogen secondary battery according to the embodiments described finer alloy structure, compared with the battery of Comparative Example was formed in AB ₅ type hydrogen storage alloy having a conventional coarse grains , High capacity, long life, and good high rate discharge.

Next, the temperature characteristics of the secondary battery using the hydrogen storage alloy according to the present invention will be described based on the following examples.

Examples 27 to 33 Various raw material powders were blended so as to have the alloy composition shown in the left column of Table 4, and the raw material powder for each example was heated and melted in a vacuum furnace in the same manner as in Example 1 to obtain an alloy. Each molten metal (master alloy) was prepared, and each molten alloy was prepared by the single roll method under the same conditions as in Example 1 to obtain a flake-shaped alloy sample.

Next, each alloy sample was heat-treated under the conditions shown in Table 4 and then classified to obtain a hydrogen storage alloy powder according to each Example, and the average crystal grain size was measured in the same manner to obtain the results shown in Table 4. .

Further, a 4 / 3A size secondary battery of 4000 mAh specification was prepared using the hydrogen storage alloy powder of each of the examples, and the capacity, life and high rate discharge ratio were measured under the same conditions as in Example 1. The results shown in Table 4 below were obtained. Further, a paste-like electrode was prepared using the hydrogen storage alloy powder according to each example. The obtained electrodes were evaluated under the same conditions as the capacity evaluation of Example 1. After reaching the maximum discharge capacity at room temperature (25 ° C.), the evaluation temperature was changed to the high temperature side (60 ° C.) and the low temperature side (−15 ° C.). Similarly, measure the capacitance C by changing
Capacitance changes at high temperature and low temperature with respect to room temperature were measured as temperature characteristics, and the results shown in Table 4 below were obtained. The measurement results for the batteries according to Comparative Examples 1 and 2 are also shown.

[0098]

[Table 4]

As is clear from the results shown in Table 4 above,
Having a predetermined composition, in the nickel-hydrogen secondary battery according to the embodiments described finer alloy structure, compared with the battery of Comparative Example was formed in AB ₅ type hydrogen storage alloy having a conventional coarse grains And high capacity, and high rate discharge property is also good.
Further, the atomic ratio a corresponding to the R component content is set to 0.4 to 0.6.
With the above range, the temperature dependence of the capacity of the alloy of each embodiment is small, and a high capacity secondary battery that is thermally stable over a wide temperature range is obtained.

Next, the characteristics of a battery using a hydrogen storage alloy in which the atomic ratio a of the R component to the total amount of the R component and the M component is in the range of 0.7 to less than 1 will be described based on the following examples. I do.

Examples 34 to 43 Various raw material powders were blended so as to have the alloy compositions shown in the left column of Table 5, and the raw material powders for Examples 42 to 43 were mechanically treated in a hydrogen atmosphere in the same manner as in Example 9. Alloying (M
A) Processing was performed to obtain powdery alloy samples.

On the other hand, the raw material powders for Examples 34 to 41 were heated and melted in a vacuum furnace to prepare molten alloys (master alloys), and each molten alloy was prepared by the single roll method under the same conditions as in Example 1. A flake-like alloy sample was obtained.

Next, each alloy sample was heat-treated under the conditions shown in Table 5 and then classified to obtain a hydrogen storage alloy powder according to each Example, and the average crystal grain size was measured in the same manner to obtain the results shown in Table 5. .

Further, a 4 / 3A size secondary battery of 4000 mAh specification was prepared using the hydrogen storage alloy powder of each example, and the capacity, life and high rate discharge ratio were measured under the same conditions as in the above example 1. The results shown in Table 5 below were obtained. The measurement results for the batteries according to Comparative Examples 1 and 2 are also shown.

[0105]

[Table 5]

As is clear from the results shown in Table 5 above,
Having a predetermined composition, in the nickel-hydrogen secondary battery according to the embodiments described finer alloy structure, compared with the battery of Comparative Example was formed in AB ₅ type hydrogen storage alloy having a conventional coarse grains , High capacity, long life, and good high rate discharge.

Next, the rising characteristics (easiness of initial activation) of a secondary battery using the hydrogen storage alloy according to the present invention will be described based on the following examples.

Examples 44 to 49 Various raw material powders were blended so as to have the alloy composition shown in the left column of Table 6, and the raw material powder for each example was heated and melted in a vacuum furnace in the same manner as in Example 1. Each molten alloy (master alloy) was prepared, and each molten metal was prepared by the single roll method under the same conditions as in Example 1 to obtain a flake-shaped alloy sample.

Next, each alloy sample was heat-treated under the conditions shown in Table 6 and then classified to obtain a hydrogen storage alloy powder according to each Example, and the average crystal grain size was measured in the same manner to obtain the results shown in Table 6. .

Further, a 4 / 3A size secondary battery of 4000 mAh specification was prepared using the hydrogen storage alloy powder of each of the examples, and the capacity, life and high rate discharge ratio were measured under the same conditions as in the example 1. The results shown in Table 6 below were obtained. Also,
After quenching, the hydrogen storage alloy powder according to each of the examples obtained by pulverization was pasted under the same conditions as in Example 1 and subjected to capacity evaluation with a single electrode. Here, as in the case of the above-mentioned capacity evaluation method, the rising characteristics of the capacity were determined as follows: after charging to 400 mAh / g at a current value of 200 mA per gram of alloy (200 mA / g), the above-mentioned current value was applied to the Hg / HgO reference electrode.
The battery was discharged until the potential reached 0.5 V, and the charge and discharge were repeated, and the number of cycles until the amount of discharge reached the maximum was measured as the number of times of activation. The measurement results for the batteries according to Comparative Examples 1 and 2 are also shown.

[0111]

[Table 6]

As is clear from the results shown in Table 6 above,
Having a predetermined composition, in the nickel-hydrogen secondary battery according to the embodiments described finer alloy structure, compared with the battery of Comparative Example was formed in AB ₅ type hydrogen storage alloy having a conventional coarse grains And high capacity, and high rate discharge property is also good.
Further, the atomic ratio a corresponding to the R component content is set to 0.8 to 0.9.
In the alloys in the range, the number of times of activation is small, and a secondary battery having a good capacity rising characteristic is obtained.

[0113]

As described above, according to the hydrogen storage alloy of the present invention, the type of various elements constituting the alloy and the composition ratio thereof are properly set, and the fine crystalline phase excellent in hydrogen storage characteristics is obtained. Is formed in the alloy structure, so that a hydrogen storage alloy having excellent hydrogen storage characteristics and corrosion resistance can be obtained. Therefore, when this alloy is used as a negative electrode material, a nickel-hydrogen secondary battery having a large battery capacity, a long life, and excellent high-rate discharge performance can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the configuration of a hydrogen storage alloy manufacturing apparatus using a single roll method.

FIG. 2 is a cross-sectional view showing a configuration of a hydrogen storage alloy manufacturing apparatus using a twin-roll method.

FIG. 3 is a perspective view showing a configuration example of a nickel-metal hydride secondary battery according to the present invention, partially cut away;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cooling chamber 2 Ladle 3 Hydrogen storage alloy melt 4 Pouring nozzle 5, 5a, 5b Cooling roll 6 Hydrogen storage alloy 7 Melting furnace 8 Tundish 11 Hydrogen storage alloy electrode (negative electrode) 12 Non-sintered nickel electrode (positive electrode) DESCRIPTION OF SYMBOLS 13 Separator 14 Container 15 Hole 16 Sealing plate 17 Insulating gasket 18 Positive electrode lead 19 Positive electrode terminal 20 Safety valve 21 Insulating tube 22 Flange paper d Gap

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22F 1/16 C22F 1/16 A H01M 4/38 H01M 4/38 A 10/30 10/30 Z // B22D 11/06 360 B22D 11/06 360B 360C C22F 1/00 601 C22F 1/00 601 641 641A 661 661A 681 681 682 682 (72) Inventor Fumiyuki Kawashima 8 Shinsugitacho, Isogo-ku, Yokohama-shi, Kanagawa Pref. 72) Inventor Shusuke Inada 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside the Toshiba Yokohama Works Co., Ltd. (72) Inventor Noriaki Sato 8 Shin-Sugita-cho, Isogo-ku, Yokohama-shi Kanagawa Prefecture Inside the Toshiba Yokohama Works Co., Ltd.

Claims (7)

[Claims] 1. General formula (R _a M _1-a ) _100-b T _b (where R is at least one element selected from La, Ce, Pr, Nd, Sm and Y, and M is Ti, Z
r, Hf, V, Nb, Ta, Cr, Mo and W are at least one element selected from the group consisting of Mn, F
e, Co, Ni, Cu, Zn, B, Al, Si and S
n is at least one element selected from n, a is an atomic ratio of 0 <a <1, and b is an atomic% of 30 ≦ b ≦ 80.
It is. A hydrogen storage alloy comprising an alloy represented by the formula (1), wherein a fine crystal phase having a crystal grain size of 10 μm or less is precipitated in at least a part of the alloy structure. 2. The hydrogen storage alloy according to claim 1, wherein the average crystal grain size of the alloy is in the range of 1 nm to 5 μm. 3. The atomic ratio a of the R component contained in the alloy is 0.
The hydrogen storage alloy according to claim 1, wherein <a ≦ 0.3. 4. The hydrogen storage alloy according to claim 1, wherein the atomic ratio a of the R component contained in the alloy satisfies 0.3 <a ≦ 0.7. 5. The hydrogen storage alloy according to claim 1, wherein the atomic ratio a of the R component contained in the alloy satisfies 0.7 <a <1. 6. A general formula (R _a M _1-a ) _100-b T _b (where R is at least one element selected from La, Ce, Pr, Nd, Sm and Y, and M is Ti, Z
r, Hf, V, Nb, Ta, Cr, Mo and W are at least one element selected from the group consisting of Mn, F
e, Co, Ni, Cu, Zn, B, Al, Si and S
n is at least one element selected from n, a is an atomic ratio of 0 <a <1, and b is an atomic% of 30 ≦ b ≦ 80.
It is. An alloy having a composition represented by the formula (1) and having a non-equilibrium phase formed in at least a part of the alloy structure is prepared, and then the obtained alloy is heat-treated to obtain fine crystals having an average crystal grain size of 1 nm to 5 μm. A method for producing a hydrogen storage alloy, comprising precipitating a phase. 7. General formula (R _a M _1-a ) _100-b T _b (where R is at least one element selected from La, Ce, Pr, Nd, Sm and Y, and M is Ti, Z
r, Hf, V, Nb, Ta, Cr, Mo and W are at least one element selected from the group consisting of Mn, F
e, Co, Ni, Cu, Zn, B, Al, Si and S
n is at least one element selected from n, a is an atomic ratio of 0 <a <1, and b is an atomic% of 30 ≦ b ≦ 80.
It is. ), And a positive electrode containing a nickel oxide and a negative electrode containing a hydrogen storage alloy in which a fine crystal phase having a crystal grain size of 10 μm or less is precipitated in at least a part of the alloy structure. A nickel-metal hydride secondary battery, wherein a nickel-hydrogen secondary battery is housed in a sealed container with an insulating separator interposed therebetween, and the sealed container is filled with an alkaline electrolyte.