JP2000265235A - Hydrogen storage alloy, its manufacture, and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain plateau pressure within a practical range, to improve hydrogen occluding/releasing property, to lower initial activation temperature, to facilitate pulverization, and to improve compactibility by providing a specific composition consisting of V, Ti, Ni, and Zr. SOLUTION: The alloy has a composition represented by general formula VxTiaNibZrc (where the symbols (x), (a), (b), and (c) are atomic %; ratios of respective constituent elements and 85<=x<98, 0<a<=7, 0<b<=7, and 1<=c<=7 are satisfied). The blending ratio of V, Ti, Ni, and Zr in a raw material is regulated so that the above composition is obtained, and the raw material is alloyed by using a heating and melting process, or the like. The resultant alloy is heat treated in a hydrogen atmosphere. It is preferable that the heat treatment is carried out by using a high temperature vacuum furnace, evacuating the furnace, introducing high purity hydrogen, raising temperature to >=100 deg.C, and performing holding for 1-2 hr. Then, the alloy is pulverized. It is desirable to regulate the average particle size after pulverization to 20 to 60 μm in the case where the alloy is compacted in the subsequent stage and used for a cathode of a secondary battery.

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 secondary battery, and more particularly, to a hydrogen storage alloy having a plateau pressure within a practical range, excellent hydrogen storage and release characteristics, and an initial activation temperature. The present invention relates to a hydrogen storage alloy which is low in pulverization, easy to pulverize, and excellent in formability, a method for producing the same, and a secondary battery using the hydrogen storage alloy as a negative electrode.

[0002]

2. Description of the Related Art With the development of electronic technology, hydrogen storage alloys have been used as driving battery materials for personal computers, mobile phones, power tools and the like. In the automotive industry, the need for global environmental protection has led to the use of hydrogen storage alloys as electrodes for secondary batteries for electric vehicles powered by electricity, which is a low-pollution, clean energy source. I have.

[0003] In addition, hydrogen storage alloys are being used not only for battery electrodes, but also for thermal energy conversion systems and hydrogen storage systems.

[0004] The characteristics required of the hydrogen storage alloy to satisfy these uses are that the amount of hydrogen that can be stored by the hydrogen storage alloy itself is absolutely large and that hydrogen can be reversibly stored and released.

In recent years, in order to improve these characteristics,
The composition, crystal structure, and manufacturing method of a hydrogen storage alloy have been studied in many aspects.

[0006] The hydrogen storage alloy has AB ₅
Type compound, AB ₂ (Laves) type compound, bcc
Are known A _{x B} y _(BCC alloy) type alloy having a crystalline structure, currently, the hydrogen storage alloy in practical use are AB ₅ type compound is the mainstream.

However, the hydrogen storage capacity of the hydrogen storage alloy of this type are, for example M _m Ni 5 in _(misch metal nickel) type as low as about 1.4 wt%, the practical use of other types of hydrogen storage alloy is Expected.

Among them, a V-based solid solution type hydrogen storage alloy, which is a BCC alloy, has a very large hydrogen storage capacity and is abundant in raw material resources, and is therefore widely used for transporting and storing hydrogen. Is expected.

[0009] Masuo Okada and Kamegawa Atsusoku such as Tohoku University Graduate School of Engineering, in the study group "protium new features" that took place in January 21 and 22, 1999, generally a V in the main component formula V _{x Ti a Ni b Zr c (71} .
4 ≦ x ≦ 80.0; 6.6 ≦ a, b, c ≦ 9.4), and a report has been made that a high hydrogen storage amount was obtained.

V is known as a single metal which is the only metal capable of storing and releasing a large amount of hydrogen at normal temperature and near normal pressure. For example, as shown in JP-A-6-228699 and JP-A-7-268514, A hydrogen storage alloy utilizing the characteristics of V has been proposed.

[0011]

However, in these V-based hydrogen storage alloys, the initial activation temperature increases as the amount of V in the composition increases in order to increase the amount of hydrogen storage. Cannot be used at present, and the maximum content of V is limited.

Further, when the content of V in the V-based hydrogen storage alloy increases, the toughness of the alloy increases, which makes it extremely difficult to pulverize. When the pulverization of the hydrogen storage alloy becomes difficult, it becomes difficult to form the hydrogen storage alloy into a predetermined shape, and its industrial use is limited.

The present invention has been made in view of such circumstances, has a plateau pressure within a practical range, has excellent hydrogen storage and release characteristics, has a low initial activation temperature, is easy to pulverize,
An object of the present invention is to provide a hydrogen storage alloy excellent in formability, a method for producing the same, and a secondary battery using the hydrogen storage alloy as a negative electrode.

[0014]

Means for Solving the Problems] To achieve the above object, the hydrogen storage alloy according to a first aspect of the present invention is represented by the general formula V as a main component V _x Ti _a Ni _b Zr _c A hydrogen storage alloy, wherein x, a, b and c indicating the atomic percentage ratio of V, Ti, Ni and Zr are 85 ≦
x <98, 0 <a ≦ 7, 0 <b ≦ 7, 1 ≦ c ≦ 7.

A method for producing a hydrogen storage alloy according to a first aspect of the present invention is a method for producing a hydrogen storage alloy from a raw material containing V, Ti, Ni and Zr, wherein V is a main component and a general formula V _x Ti _a Ni _b Zr
_c , an alloy represented by V, Ti, Ni and Z
x, a, b and c representing the atomic percent ratio of r are 8
An alloy having a composition ratio of 5 ≦ x <98, 0 <a ≦ 7, 0 <b ≦ 7, and 1 ≦ c ≦ 7 is manufactured.

A hydrogen storage alloy according to a second aspect of the present invention
Is based on the general formula V_xTi_a Ni_bZr_c
A hydrogen storage alloy represented by the formula: V, Ti, Ni and
X, a, b and c indicating the atomic percentage ratio of Zr and Zr
Is 90 ≦ x <98, 0 <a ≦ 7, 0 <b ≦ 7, 1 ≦ c
≦ 7.

A method for producing a hydrogen storage alloy according to a second aspect of the present invention is a method for producing a hydrogen storage alloy from a raw material containing V, Ti, Ni and Zr, wherein V is a main component and a general formula V _x Ti _a Ni _b Zr
_c , an alloy represented by V, Ti, Ni and Z
x, a, b and c representing the atomic percent ratio of r are 9
An alloy having a composition ratio of 0 ≦ x <98, 0 <a ≦ 7, 0 <b ≦ 7, and 1 ≦ c ≦ 7 is manufactured.

The hydrogen storage alloy according to the present invention is a V-based solid solution type hydrogen storage alloy having a body-centered cubic structure, and oxygen contained as an impurity is preferably contained in a total of 10,000 pP.
pm or less, more preferably 7500 ppm or less, particularly preferably 5000 ppm or less. In the present invention, the method for reducing the content of oxygen contained in the hydrogen storage alloy is not particularly limited, a method using a low oxygen content as a raw material to be used, the raw material is covered with zirconium foil, A method such as a method of performing a vacuum heat treatment and a method of purifying a raw material by a zone melt method can be employed.

The hydrogen storage alloy according to the present invention is a conventional hydrogen storage alloy.
Since the V content is much higher than that of the Ti—Ni-based hydrogen storage alloy, the hydrogen storage amount is large, and further, by optimizing the composition of V, Ti, Ni, and Zr, the hydrogenation rate decreases and the initial activation temperature increases. Has solved the problem.

That is, the general formula V _X Ti _a Ni _b
V group solid solution hydrogen storage alloy of body-centered cubic structure represented by Zr _c is practically optimum temperature initial activation is completed at (room temperature), within a few minutes or more of hydrogen 2.0 wt% It can be inserted and released reversibly in a short time.

Also, by changing the composition of the alloy,
The plateau pressure (herein referred to as the dissociation equilibrium pressure) can be set to any value within a practical range of 0.1 to 1.0 MPa. A hydrogen storage alloy having a plateau pressure in such a range is preferable because, when the plateau pressure is too low, there is a tendency that hydrogen release at the use environment temperature becomes difficult, and when the plateau pressure is too high, the operability is reduced. And the pressure resistance of the device containing the alloy is required.

In the present invention, the general formula V _x Ti _a Ni
In the hydrogen-absorbing alloy represented by _b Zr _c, V, T
x, a, indicating the atomic percent ratio of i, Ni and Zr
b and c are 85 ≦ x <98 (preferably 90 ≦ x <
98), 0 <a ≦ 7, 0 <b ≦ 7, 1 ≦ c ≦ 7. However, x + a + b + c does not become 100.
This is because the raw materials used contain impurities other than the above constituent elements. Also, during the production process of the alloy, impurities such as carbon may be mixed.

The reasons for limiting the composition will be described below. In the present invention, if x (V) is too small, the hydrogen storage amount tends to decrease. If it is too large, the initial activation temperature becomes too high, making the initial activation difficult and impractical. According to the present invention, a hydrogen storage amount of 1.75% by weight, preferably 2.0% by weight or more based on the total weight of the alloy can be realized. Further, according to the present invention, initial activation at around normal temperature (25 ° C.) becomes possible.

In the present invention, when a (Ti) is 0, the amount of hydrogen occlusion decreases, and when a (Ti) exceeds 7, the plateau pressure decreases, which is not practical.

In the present invention, when b (Ni) is 0, not only does the plateau pressure decrease, but even if an electrode is formed, the alloy itself has no electrode activity, so that it becomes difficult to use it as an electrode. On the other hand, when b (Ni) exceeds 7, the hydrogen storage amount decreases, which is not practical.

In the present invention, if c (Zr) is less than 1, initial activation is difficult, the hydrogenation rate is slow, and it takes time to absorb hydrogen. Less practical. The higher the hydrogenation rate, the better, and the shorter the time for storing hydrogen, the better. When a hydrogen storage alloy is used as an electrode, the current density decreases when the hydrogenation rate is low. Also, even when applied to hydrogen storage, heat storage, heat pump, and the like, the higher the hydrogenation rate, the better. In the hydrogen storage alloy according to the present invention, the amount of hydrogen in the alloy increases by 8% when equilibrium is reached.
The time required to reach 0% (80% occlusion time) can be shortened within several minutes, preferably within 90 seconds, and more preferably within 60 seconds.

In the present invention, the oxygen contained in the hydrogen storage alloy is preferably not more than 10,000 ppm (more preferably not more than 7,500 ppm, particularly preferably not more than 5000 ppm) of the whole alloy, if the oxygen content is too large. This is because the hydrogen storage amount tends to decrease and the hydrogenation rate tends to decrease as the initialization temperature increases. In particular, in the hydrogen storage alloy according to the present invention having a V content of 90 atomic% or more, oxygen contained in the hydrogen storage alloy is preferably 7500 ppm or less, more preferably 5000 ppm or less in the entire alloy.

By the way, the hydrogen storage alloy according to the present invention is
In order to apply to a battery electrode or a hydrogen storage alloy for a fuel cell, it is necessary to pulverize the hydrogen storage alloy during the manufacturing process. However, when the V content is 85 atomic%, especially 90 atomic% or more, the toughness of the alloy becomes extremely high, and the pulverization becomes difficult.

In order to solve this problem, the present invention proposes a heat treatment method in a hydrogen atmosphere in which a hydrogen storage alloy before pulverization is heat-treated in a hydrogen atmosphere. That is, the method for producing a hydrogen storage alloy according to the present invention includes an alloying step of producing an alloy from a raw material containing V, Ti, Ni, and Zr; and a heat treatment step in a hydrogen atmosphere in which the alloy is heat-treated in a hydrogen atmosphere. Having.

In the present invention, the specific method of the alloying step is not particularly limited, and a method of preparing a molten metal by arc melting or high frequency melting and solidifying the molten metal by cooling, and a method of mechanical alloying Or an electrolytic deposition method from an aqueous solution. Among these, the production method using a molten metal is particularly preferable because the uniformity of the alloy is increased.

The method for producing a hydrogen storage alloy according to the present invention comprises:
A pulverizing step of pulverizing the alloy heat-treated in a hydrogen atmosphere;
A forming step of forming the pulverized alloy into a predetermined shape.

The heat treatment temperature in the heat treatment step under the hydrogen atmosphere is not particularly limited, but is preferably 100 ° C.
The temperature is more preferably at least 200 ° C, particularly preferably at least 300 ° C. If the heat treatment temperature is too low, pulverization is not easy. The upper limit of the heat treatment temperature in the heat treatment step under a hydrogen atmosphere is not particularly limited, but is preferably 900 ° C. or lower, more preferably 600 ° C.
It is as follows. Even if the heat treatment temperature is too high, the effect of facilitating pulverization is small and economical.

Specific applications of the hydrogen storage alloy according to the present invention are not particularly limited, and include a negative electrode for a secondary battery, a hydrogen supply source for a fuel cell, a hydrogen storage container, and a hydrogen fuel tank (for example, for automobiles). It can be widely used in applications such as hydrogen compressors, heat pumps, hydrogen purifiers, isotope separators, refrigeration systems, sensors, actuators, power generation systems, and chemical engines. Above all,
The hydrogen storage alloy according to the present invention is preferably used as a negative electrode for a secondary battery.

A secondary battery according to the present invention is a secondary battery including a negative electrode, a positive electrode, and an electrolyte interposed between the negative electrode and the positive electrode. formula main component _V x _Ti a _Ni b Zr
x, a, b and c containing a hydrogen storage alloy represented by _c and indicating the atomic percentage ratio of V, Ti, Ni and Zr
Is 85 ≦ x <98 (preferably 90 ≦ x <98), 0
<A ≦ 7, 0 <b ≦ 7, 1 ≦ c ≦ 7.

The electrolyte may be a solid electrolyte or a liquid electrolyte. As the liquid electrolyte, for example, a potassium hydroxide electrolyte or the like is used. The electrolyte is
It may be used by impregnating a separator or the like made of a nonwoven fabric or the like. The positive electrode is not particularly limited, but is formed into a paste of nickel hydroxide powder together with a binder and a conductive additive, and after filling into a foamed nickel substrate or nickel fiber substrate having a porosity of 95% or more, pressure molding is performed. An electrode or the like can be preferably used.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments shown in the drawings. 1A and 1B are conceptual diagrams of a secondary battery according to an embodiment of the present invention, FIG. 2 is a block diagram of a sample of a hydrogen storage alloy according to an example of the present invention, and FIG. PC of hydrogen storage alloy according to one embodiment
It is a graph which shows a T line.

Production method of hydrogen storage alloy (1) Preparation of raw materials V, Ti, Ni and Zr are weighed at a predetermined composition ratio. Vanadium (V), titanium (Ti), nickel (Ni) and zirconium (Z
The purity of r) is preferably at least 99% by weight.

[0038] V in the raw material, Ti, mixing ratio of Ni and Zr hydrogen storage alloy obtained after production is represented by the general formula _V x _Ti a _Ni b Zr _c, V, Ti,
X, a, b and c indicating the atomic percentage ratio of Ni and Zr are 85 ≦ x <98 (preferably 90 ≦ x <9
8), 0 <a ≦ 7, 0 <b ≦ 7, and 1 ≦ c ≦ 7. The atomic percentage ratio of V, Ti, Ni, and Zr in the manufactured hydrogen storage alloy can be determined, for example, by X-ray fluorescence composition analysis, high-frequency induction plasma emission (I
CP) It can be measured by a composition analysis method or the like.

(2) Alloying As a method for producing an alloy from a raw material, there are a heat melting method and a synthesis method (reduction diffusion method, chemical synthesis method, mechanical alloying method). Method.

The heating melting method is not particularly limited, and examples thereof include a high frequency melting method and an arc melting method. The high frequency melting method includes a mold casting method, a gas atomizing method, a melt spinning method, and the like. In the present embodiment, the arc melting method is preferable. In order to homogenize the obtained alloy, it is preferable to repeat melting several times or more. At the time of arc melting, it is preferable that the inside of the melting furnace is evacuated, an inert gas is introduced, and the arc melting is performed in an inert gas atmosphere. The inert gas is not particularly limited, but argon gas or the like is preferably used.

(3) Heat treatment in a hydrogen atmosphere The alloy obtained in the alloying step is then heat-treated in a hydrogen atmosphere. The heat treatment in a hydrogen atmosphere is preferably performed in a sealed container, for example, using a high-temperature vacuum furnace. When performing heat treatment in a hydrogen atmosphere in a high-temperature vacuum furnace,
After the inside of the furnace is evacuated to a vacuum pressure of 10 ⁻² Pa or less, high-purity hydrogen of preferably 1 to 10 atm is introduced, and then the temperature is raised to a predetermined temperature (heat treatment temperature). Hold for 1-2 hours. The purity of hydrogen is preferably 99.9999% or more.
The heat treatment temperature in the heat treatment under a hydrogen atmosphere is preferably 100 ° C. or higher.

(4) Pulverization and Forming The hydrogen storage alloy heat-treated in the hydrogen atmosphere as described above can be used as it is depending on the application, but in the present embodiment, it is pulverized. As the grinding method,
Although not particularly limited, a method using a stamp mill, a method using a crusher, and the like are exemplified. The average particle size of the alloy particles after pulverization is determined depending on the use and the like, and is not particularly limited. preferable.

Although the pulverized hydrogen storage alloy may be used as it is depending on the application, in the present embodiment, it is formed into a predetermined shape. The method for forming the pulverized hydrogen storage alloy into a predetermined shape is not particularly limited, but when forming into a block shape, a method using a powder metallurgy method or a method using copper by electroless plating. A method such as microencapsulation is used.
The method for forming the pulverized hydrogen storage alloy into a sheet is not particularly limited, but a doctor blade method, an extrusion method, a calendering method, or the like can be used.

When the hydrogen storage alloy of the present embodiment is used as a negative electrode of a secondary battery, an appropriate amount of a conductive additive may be added to the alloy powder during molding to form a predetermined shape.
Nickel powder, carbon powder, copper powder and the like can be used as the conductive assistant. If necessary, a binder may be added to the alloy powder. The binder is not particularly limited, but fluororesins such as FEP and PTFE are preferably used.

When the hydrogen storage alloy of the present embodiment is used as a negative electrode of a secondary battery, the hydrogen storage alloy powder is formed into a paste together with a thickening aid such as a binder, a conductive aid, and CMC. The negative electrode may be formed by filling the paste into a foamed nickel substrate or nickel fiber substrate and press-molding the paste.

(5) Activation of Electrode When the hydrogen storage alloy of the present embodiment is used as a negative electrode of a secondary battery, the electrode is activated after the battery is assembled. At the time of activation, charging and discharging of the battery are repeated at normal temperature, and when the discharge capacity becomes constant, it is considered that the activation has been completed. In the present embodiment, V _x Ti having the above-described composition is used as the negative electrode material.
due to the use of hydrogen storage alloy consisting of _a Ni _b Zr _c, it is possible activation at room temperature, moreover, the possible activation with a small number of cycles, excellent hydrogen storage characteristics, the secondary battery Performance is improved.

Structure of Secondary Battery The hydrogen storage alloy according to the present invention can be used, for example, as the negative electrode 6 of the secondary battery 2 or 2a shown in FIGS. 1 (A) and 1 (B). Secondary battery 2 shown in FIG.
Has a positive electrode 4 and a negative electrode 6 in an alkaline electrolyte. At the negative electrode 6, charging is performed by absorbing hydrogen atoms of water molecules, and discharging is performed by releasing hydrogen atoms. It can be carried out.

The alkaline electrolyte is not particularly limited, but for example, an aqueous potassium hydroxide solution can be used. The electrolytic solution may be used by impregnating a separator made of a nonwoven fabric or the like. In addition, the positive electrode 4
Although not particularly limited, an electrode or the like which is obtained by forming a nickel hydroxide powder into a paste together with a binder and a conductive aid into a foamed nickel substrate or a nickel fiber substrate having a porosity of 95% or more, and then press-forming. It can be preferably used.

Further, recently, as shown in FIG. 1B, a secondary battery in which the positive electrode 4 and the negative electrode 6 are in solid contact with each other via a solid electrolyte 8a has been developed. As the solid electrolyte 8a, a proton conductive solid electrolyte such as molybdophosphoric acid 29 hydrate, antimony pentoxide hydrate, zirconium oxide 2.3 hydrate, and tetramethyl ammonium hydroxide pentahydrate can be used. .

The present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the present invention. For example, the hydrogen storage alloy according to the present invention can be used for all purposes for storing and releasing hydrogen, other than as a negative electrode for a secondary battery.

[0051]

EXAMPLES Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.

Embodiment 1 FIG. 2 is a block diagram showing the fabrication of a hydrogen storage alloy sample in this embodiment. As shown in FIG. 2, first, commercially available V (purity 99.7% by weight), Ti (purity 99.5% by weight), Ni
(Purity: 99.97% by weight) and Zr (Purity: 99.5% by weight) were weighed at a predetermined composition ratio so that the alloy weight was 20.0 g.

This raw material was arc-melted in a water-cooled copper hearth under a 67 kPa argon atmosphere. Dissolution current is 250
A. The melting time was 2 minutes, and the alloy was turned upside down and melted a total of three times in order to homogenize the alloy.

About half of the produced alloy was heat-treated at 500 ° C. in a hydrogen atmosphere.

The heat treatment under a hydrogen atmosphere uses a high-temperature vacuum furnace.
After degassing to 4 × 10 ⁻³ Pa, 1 atm of high-purity hydrogen (9
9.9999%), and then a predetermined temperature (500
(° C.) and maintained at this temperature for 1 hour.

The alloy heat-treated in a hydrogen atmosphere was pulverized by a stamp mill in an argon atmosphere. The particle size is 1.
4 mm or less and 1.4 mm to 2.0 mm, and for subsequent experiments and tests, 1.4 mm to 2.0 mm.
mm sample was used.

Next, the details of the experiments and tests will be described.
2.0 g of the sample prepared by the above procedure is placed in a stainless steel tube, and the pressure is reduced to 1.3 Pa, and then hydrogen is introduced. The pressure was 9.5 MPa, and the temperature at which hydrogen was absorbed was measured. The initial temperature was room temperature (25 ° C.), but samples not activated at this temperature were heated in an electric furnace. The temperature at which hydrogen was stored while heating was used as the initial activation temperature.

Next, the stainless steel tube was placed in a constant temperature water bath adjusted to 40 ° C., and subjected to stabilization treatment (vacuum state and H of 7 MPa).
(Repeat of ₂ atmosphere states) was performed three times, and then a pressure-composition isotherm (PCT line) was measured at this temperature. The measurement of the PCT line is basically performed according to JIS H7201.
Was performed according to V as a main component and the general formula V _x Ti _a N
The hydrogen-absorbing alloy samples 1-9 represented by i _b Zr _c,
The atomic percent ratio of V, Ti, Ni and Zr (x,
Each was manufactured by the above-mentioned manufacturing method so that a, b, and c) had the composition ratios shown in Table 1. The atomic% ratio is determined by using a composition analyzer based on a fluorescent X-ray method (product number: Simultix3 manufactured by Rigaku Denki Co., Ltd.)
550).

The samples 1 to 9 were tested for hydrogen storage capacity, plateau pressure and initial activation temperature, and the results shown in Table 1 below were obtained. In Table 1, at% indicates atomic%, and wt% indicates weight%. FIG. 3 shows the PCT line of Sample 7. In FIG. 3, a flat portion indicated by a symbol P1 is a plateau pressure on the hydrogen release side, and Tables 1 to 7 show the results of measuring the plateau pressure for each sample. In each of Tables 1 to 7 below, * indicates a sample in a preferred range in each table, and ** indicates a sample in a more preferred composition range.

[0060]

[Table 1]

As shown in Table 1, when the V composition is 85 atomic% or more, preferably 90 atomic% or more, 1.8% by weight or more, preferably 2.0% by weight or more of satisfactory hydrogen storage It was confirmed that the amount was obtained. The larger the V composition, the larger the hydrogen storage amount. However, it was confirmed that at 98 atomic%, the initial activation temperature sharply increased, and the initial activation treatment of the hydrogen storage alloy became difficult.

Although the plateau pressure increased with the V composition, it was practically no problem (0.1-1.
0 MPa).

Next, an experiment was conducted to determine whether these alloys could be used as a negative electrode for an alkaline secondary battery. In the experiments, alloy samples 4 to 4 having preferable compositions shown in Table 1 were used.
8 was classified to a predetermined particle size, mixed with a Cu powder as a current collector, and a plurality of test electrodes were prepared by press molding. Using each test electrode as a negative electrode, a charge / discharge test was performed by a triode cell method, and it was confirmed that these alloys were effective as a battery electrode.

[0064] In the hydrogen-absorbing alloy represented in mainly of Example 2 V in the general formula _{V x Ti a Ni b Zr c} , as shown in Table 2 below, atomic percentage ratio of Ti to (a), 0 From 9.0 to 9.0, samples 10 to 15 were prepared, and the same tests as in Example 1 were performed. The preparation procedure of Samples 10 to 15 is the same as that of Example 1 except that the composition ratio was changed, and thus the description is omitted.

Table 2 shows the test results. When no Ti was contained, the hydrogen storage amount was small, and when the Ti composition exceeded 7 atomic%, the plateau pressure was low. It is presumed that the plateau pressure decreased because the lattice constant of the bcc phase increased due to the large atomic radius of Ti.

[0066]

[Table 2]

[0067] In the hydrogen-absorbing alloy represented in mainly of Example 3 V in the general formula _{V x Ti a Ni b Zr c} , as shown in Table 3 below, atomic percent ratio of Ni to (b), 0 The sample was changed in the range from 9.0 to 9.0, and samples 16 to 19 were produced, and the same test as in Example 1 was performed. The preparation procedure of Samples 16 to 19 is the same as that of Example 1 except that the composition ratio was changed, and thus the description is omitted.

Table 3 shows the test results. When Ni is not contained at all, the plateau pressure is too low and there is no electrode activity, so that it cannot be used as a battery electrode. If the Ni composition exceeds 7 atomic%, the plateau pressure becomes too large,
It was confirmed that the hydrogen storage amount was too low.

It is estimated that the plateau pressure increased because the lattice constant of the bcc phase was reduced due to the small atomic radius of Ni.

[0070]

[Table 3]

[0071] In the hydrogen-absorbing alloy represented in mainly of Example 4 V in the general formula _{V x Ti a Ni b Zr c} , as shown in Table 4 below, atomic% ratio of Zr to (c), 0 From 7.0 to 7.0, samples 20 to 26 were prepared, and the same test as in Example 1 was performed. The preparation procedure of Samples 20 to 26 is the same as that of Example 1 except that the composition ratio was changed, and thus the description is omitted.

Table 4 shows the test results. When Zr is not contained, activation is not sufficiently performed even at 500 ° C., but it was confirmed that activation was performed at room temperature if the Zr composition was 1 atomic% or more. Further, when the Zr composition exceeds 7 atomic%, the hydrogen storage amount decreases, which is not practical, and the plateau pressure decreases with an increase in the Zr composition. did it. Further, the hydrogenation rate decreases with a decrease in the Zr composition (80% occlusion time increases).
If the composition is 1 atomic% or more, the 80% occlusion time is within several minutes, and it has been found that there is no practical problem. Here, since the hydrogenation rate differs depending on each measuring device and measuring method, in this example, the measurement was performed according to JIS-H-7202.

However, in the test of this example, hydrogen was introduced so that the final hydrogenation pressure was about 1 MPa, and the time required for the hydrogen storage amount to reach 80% of the equilibrium state (80% storage time) was compared. did.

[0074]

[Table 4]

[0075] In the hydrogen-absorbing alloy represented in mainly of Example 5 V by the general formula _{V x Ti a Ni b Zr c} , as shown in Table 5 below, by changing the amount of oxygen contained in the alloy, Hydrogen storage capacity,
Tests were performed on plateau pressure, initial activation temperature and hydrogenation rate. Samples 4, 5 and 7 were exactly the same as Samples 4, 5 and 7 used in Example 1, respectively, and the preparation procedure of Samples 27 to 35 was except that a raw material having a relatively high oxygen content was used. Is the same as in the first embodiment, and will not be described.

Table 5 shows the test results. The oxygen content in each sample was determined using a gas analyzer (EMGA-650 series manufactured by Horiba, Ltd.).

As shown in Table 5, the oxygen content was 1000
If it is 0 ppm or less, the initial activation temperature, the hydrogen storage amount and the plateau pressure hardly change, but
When the concentration exceeds ppm, the initial activation temperature increases,
It was confirmed that the hydrogen storage amount was small. Further, it was confirmed that the hydrogenation rate was reduced as the oxygen content was increased.

[0078]

[Table 5]

Example 6 The hydrogen storage alloy was pulverized to have a predetermined particle size.
This is extremely important in the manufacturing process of the hydrogen storage alloy. In the present embodiment, it was examined how efficiently this can be performed.

Samples 36A and 37A shown in Table 6 below
Was performed in the same manner as in Example 1 except that the composition ratio was changed and the heat treatment was not performed in a hydrogen atmosphere.
Samples 36B and 37B were prepared by changing the composition ratio and performing a heat treatment temperature in a hydrogen atmosphere (hydrogenation temperature in the table).
Since this example is the same as Example 1 except for changing, the description is omitted.

In this example, in order to examine the PCT characteristics and the crushability of the alloy samples with and without heat treatment in a hydrogen atmosphere, tests of the hydrogen storage amounts and plateau pressures of these samples 36A, 36B, 37A and 37B were carried out. Performed similarly to 1. In addition, the grindability of each sample was also evaluated.
The grindability was determined by the time required for stamp mill grinding (alloy 10 g).
(The time required to grind the particles to a particle size of 1.4 to 2.0 mm).

Table 6 shows the results. It was confirmed that the amount of hydrogen occlusion and the plateau pressure did not change depending on the presence or absence of heat treatment in a hydrogen atmosphere, but the pulverizability greatly changed. this is,
This is probably because the V solid solution alloy having extremely high toughness expanded and fractured by absorbing hydrogen, and was easily divided into small pieces by a slight force.

[0083]

[Table 6]

[0084] In the hydrogen-absorbing alloy represented in mainly of Example 7 V in the general formula _{V x Ti a Ni b Zr c} , as shown in Table 7 below, changing the heat treatment temperature under the alloy composition and an atmosphere of hydrogen Samples 38A to 38D were prepared in the same manner as in Example 1, except for the amount of hydrogenation, and a test was performed on the hydrogenation amount and the pulverization time after heat treatment in a hydrogen atmosphere.

Table 7 shows the test results. The hydrogenation amount of the sample after the heat treatment in a hydrogen atmosphere was determined by a gas analyzer (EMGA-621 series manufactured by Horiba, Ltd.).

As shown in Table 7, the higher the heat treatment temperature in a hydrogen atmosphere, the easier the hydrogenation and the easier the pulverization.

[0087]

[Table 7]

[0088]

As described above, according to the present invention, a plateau pressure within a practical range, excellent hydrogen storage and release characteristics, a low initial activation temperature, easy pulverization,
A hydrogen storage alloy excellent in formability and a method for producing the same can be provided. Further, according to the present invention, a high-performance secondary battery can be realized by using the hydrogen storage alloy according to the present invention as a negative electrode.

[Brief description of the drawings]

FIGS. 1A and 1B are conceptual diagrams of a secondary battery according to one embodiment of the present invention.

FIG. 2 is a block diagram showing the production of a hydrogen storage alloy sample according to one embodiment of the present invention.

FIG. 3 is a graph showing a PCT line of the hydrogen storage alloy according to one embodiment of the present invention.

[Explanation of symbols]

 2 Secondary battery 4 Positive electrode 6 Negative electrode 8 Alkaline electrolyte 8a Solid electrolyte

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C22F 1/00 682 C22F 1/00 682 687 687 1/02 1/02 1/18 1/18 G H01M 4/38 H01M 4/38 A 8/04 8/04 J 10/30 10/30 Z (72) Inventor Ryo Fukuno 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (72) Inventor Shinichi Yamashita Tokyo 1-13-1 Nihombashi, Chuo-ku, Tokyo F-term in TDK Corporation 4K017 AA04 BA07 BB06 BB09 CA06 DA09 EA05 EA09 EK07 FA01 FB02 5H003 AA01 AA04 BA01 BA04 BB02 BC01 BD00 BD01 BD03 BD06 5H027 AA02 BA14 5H0 BB EE01 HH00 HH01 HH03 HH08

Claims (10)

[Claims] 1. A general formula mainly composed of _V V x _Ti a Ni
A hydrogen storage alloy represented by _b Zr _c, V, T
x, a, indicating the atomic percent ratio of i, Ni and Zr
b and c are 85 ≦ x <98, 0 <a ≦ 7, 0 <b ≦
7, a hydrogen storage alloy having a relationship of 1 ≦ c ≦ 7. 2. A general formula mainly composed of _V V x _Ti a Ni
A hydrogen storage alloy represented by _b Zr _c, V, T
x, a, indicating the atomic percent ratio of i, Ni and Zr
b and c are 90 ≦ x <98, 0 <a ≦ 7, 0 <b ≦
7, a hydrogen storage alloy having a relationship of 1 ≦ c ≦ 7. 3. The hydrogen storage alloy according to claim 1, wherein oxygen contained as an impurity is 10,000 ppm or less of the whole alloy. 4. A secondary battery comprising a negative electrode, a positive electrode, and an electrolyte interposed between the negative electrode and the positive electrode, wherein the negative electrode has V as a main component and a general formula V _x includes a hydrogen storage alloy represented by _{Ti a Ni b Zr c, V} , Ti, x indicating the atomic percent ratio of Ni and Zr, a, b and c is, 85 ≦ x <98,0 <
A secondary battery characterized by a relationship of a ≦ 7, 0 <b ≦ 7, and 1 ≦ c ≦ 7. 5. A secondary battery comprising a negative electrode, a positive electrode, and an electrolyte interposed between the negative electrode and the positive electrode, wherein the negative electrode has V as a main component and a general formula V _x includes a hydrogen storage alloy represented by _{Ti a Ni b Zr c, V} , Ti, x indicating the atomic percent ratio of Ni and Zr, a, b and c is, 90 ≦ x <98,0 <
A secondary battery characterized by a relationship of a ≦ 7, 0 <b ≦ 7, and 1 ≦ c ≦ 7. 6. An alloying step for producing an alloy from a raw material containing V, Ti, Ni and Zr, and a heat treatment step in a hydrogen atmosphere for heat treating the alloy in a hydrogen atmosphere.
Manufacturing method of hydrogen storage alloy. 7. The production of a hydrogen storage alloy according to claim 6, further comprising: a pulverizing step of pulverizing the alloy heat-treated in the heat treatment step in a hydrogen atmosphere; and a forming step of forming the pulverized alloy into a predetermined shape. Method. 8. The method for producing a hydrogen storage alloy according to claim 6, wherein a heat treatment temperature in the heat treatment step in a hydrogen atmosphere is 100 ° C. or higher. 9. A raw material containing V, Ti, Ni and Zr, wherein V is a main component and a general formula V _x Ti _a Ni _b Zr
_c , an alloy represented by V, Ti, Ni and Z
x, a, b and c representing the atomic percent ratio of r are 8
A method for producing a hydrogen storage alloy, comprising producing an alloy having a composition ratio of 5 ≦ x <98, 0 <a ≦ 7, 0 <b ≦ 7, and 1 ≦ c ≦ 7. 10. A raw material containing V, Ti, Ni and Zr, wherein V is a main component and a general formula V _x Ti _a Ni _b Zr
_c , an alloy represented by V, Ti, Ni and Z
x, a, b and c representing the atomic percent ratio of r are 9
A method for producing a hydrogen storage alloy, comprising producing an alloy having a composition ratio of 0 ≦ x <98, 0 <a ≦ 7, 0 <b ≦ 7, and 1 ≦ c ≦ 7.