JPH08319529A - Hydrogen storage alloy and hydrogen storage alloy electrode - Google Patents

Abstract

PURPOSE: To provide a hydrogen storage alloy, in which alloy phase is composed essentially of C15 (MgCu2 ) type Laves phase and which has excellent high temp. retention property, by specifying a composition consisting of Zr, Mn, V, Al, Co, Fe, Cu, Zn, Cr, and Ni. CONSTITUTION: This alloy is a hydrogen storage alloy, which has a composition represented by general formula ZrMna Vb Mx Cry Niz or Zr1.1-w Tiw Mna Vb Mx Cry Niz [where M is Al, Co, Fe, Cu, Zn and the symbols (a), (b), (w), (x), (y), and (z) stand for 0.1-0.4, 0.05-0.3 or 0.1-0.4, 0-0.5, >0-0.2, >0-0.2, and 1.1-1.4, respectively, and 2.0<=a+b+x+y+z<=2.4 or 1.7<=(a+b+x+y+z)/1.1<=2.2 is satisfied and, preferably, 1.3<=x+z is satisfied] and in which alloy phase is composed essentially of C15 (MgCu2 ) type Laves phase, and has excellent high temp. retention property. By using this alloy as an electrode, an alkali storage battery, improved in high temp. retention property and having high reliability, can be obtained.

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 capable of reversibly electrochemically storing and releasing hydrogen, and a hydrogen storage alloy electrode using the same.

[0002]

2. Description of the Related Art A hydrogen storage alloy electrode using a hydrogen storage alloy that reversibly absorbs and releases hydrogen has a theoretical capacity density larger than that of a cadmium electrode and does not cause deformation such as a zinc electrode or dendrite formation. It is expected as a negative electrode for alkaline storage batteries that has a long life, is pollution-free, and has a high energy density. The alloy used for such a hydrogen storage alloy electrode is usually produced by an arc melting method, a high frequency induction heating melting method, or the like. Generally, a Ti-Ni-based and La (or Mm) -Ni-based multi-component alloy is used. well known. The Ti-Ni-based multi-component alloy is classified as an AB type (A: an element having a high affinity for hydrogen such as La, Zr, and Ti, and B: a transition element such as Ni, Mn, and Cr). This type of alloy exhibits a relatively large discharge capacity at the beginning of the charge / discharge cycle, but there is a problem that it is difficult to maintain the capacity for a long time when the charge / discharge is repeated. Also, AB ₅ type La (or Mm)-
Many developments have been made in recent years on Ni-based multi-component alloys as electrode materials, and in particular, Mm-Ni-based multi-component alloys have already been put to practical use. This alloy system has problems such as a relatively small discharge capacity, insufficient life performance as a battery electrode, and high material cost. Therefore, a novel hydrogen storage alloy material having a large discharge capacity and a long life is desired. On the other hand, the AB ₂ type Lavas phase alloy has a relatively high hydrogen storage capacity and is promising as an electrode having a high capacity and a long life. For this alloy system, Zr-Mn-V-Cr-Ni has already been used.
Many alloys including system alloys have been proposed.

However, when an AB ₂ type Larvus phase alloy is used for the electrode, Ti--Ni system or La (or Mm) is used.
Although the discharge capacity is larger than that of the Ni-based multi-component alloy, there is a problem that the discharge characteristics at the beginning of the charge / discharge cycle are very poor. Therefore, by adjusting the composition with a Zr-Mn-VM-Ni-based alloy (M is one or more elements selected from Fe or Co), the initial discharge characteristics are improved while maintaining a high capacity. Was proposed (Japanese Patent Laid-Open No. 5-8
2125). There is also a proposal that the high temperature storage characteristics are improved without impairing the initial discharge characteristics by adding a small amount of Cr (JP-A-5-347156).

[0004]

When a sealed battery is constructed by using the electrodes made of the Zr-Mn-VM-Ni alloy according to the former proposal, the elution of alloy components, especially Mn, into the alkaline electrolyte is achieved. However, the dissolved element is deposited in the form of a conductive oxide or the like to cause a short circuit, and there is a problem that the battery voltage immediately drops when left in a high temperature atmosphere of about 65 ° C. The latter Cr-added alloy improves the high temperature storage properties, but nevertheless 6
If the storage period at 5 ° C. exceeds 30 days, the battery voltage will be lowered. Today, ensuring the reliability of batteries is the most important issue, and the storage period at high temperature is 60
It is required to operate normally even after a lapse of days.
In view of the above, the present invention is further improved high temperature storage characteristics,
It is an object of the present invention to provide a hydrogen storage alloy electrode that provides an alkaline storage battery having high reliability.

[0005]

Means for Solving the Problems] hydrogen storage alloy of the present invention at least has the general formula _{ZrMn a V b M x Cr y} Ni z ( however, M is Al, Co, Fe, selected from the group consisting of Cu and Zn It is a kind of element, and 0.1 ≦ a <0.
4, 0.05 ≦ b ≦ 0.3, 0 <x ≦ 0.2, 0 <y ≦
0.2, 1.0 ≦ z ≦ 1.3, and 2.0 ≦ a + b + x
+ Y + z ≦ 2.4), and the main component of the alloy phase is C15.
It is a (MgCu ₂ ) type Larvus phase. The hydrogen storage alloy of the present invention have the general formula _{Zr 1.1-w Ti w Mn a} V b M x Cr y
Ni _z (where M is Al, Co, Fe, Cu and Z
at least one element selected from the group consisting of n, 0 <w ≦ 0.5, 0.1 ≦ a <0.4, 0.1 ≦ b
≦ 0.4, 0 <x ≦ 0.2, 0 <y ≦ 0.2, 1.1 ≦
z ≦ 1.4 and 1.7 ≦ (a + b + x + y + z) /
1.1 ≦ 2.2) and the main component of the alloy phase is C15
It is a (MgCu ₂ ) type Larvus phase. The above general formula Zr
_{Mn a V b M x Cr y} Ni z and _{Zr 1.1-w Ti w Mn a} V b
In M _x Cr _y Ni _z, it is preferable that 1.3 ≦ x + z.

Furthermore, the hydrogen storage alloy of the present invention have the general formula _{ZrMn a V b M x Cr y} Ni z ( however, M is Al, C
at least one element selected from the group consisting of o, Fe, Cu and Zn, and 0.4 ≦ a ≦ 0.8,0.0
5 ≦ b ≦ 0.3, 0 <x ≦ 0.2, 0.2 ≦ y ≦ 0.
5, 1.0 ≦ z ≦ 1.3 and 2.0 ≦ a + b + x + y
+ Z ≦ 2.4), the main component of the alloy phase is C15 (M
It is a gCu ₂ ) type Larvus phase. The hydrogen storage alloy of the present invention have the general formula _{Zr 1.2-w Ti w Mn a} V b M x Cr y Ni
_z (where M is at least one element selected from the group consisting of Al, Co, Fe, Cu and Zn, and 0
<W ≦ 0.6, 0.4 ≦ a ≦ 0.8, 0.1 ≦ b ≦ 0.
4,0 <x ≦ 0.2, 0.2 ≦ y ≦ 0.5, 1.1 ≦ z
≦ 1.4 and 1.7 ≦ (a + b + x + y + z) / 1.
2 ≦ 2.2), and the main component of the alloy phase is C15 (Mg
It is a Cu ₂ ) type Lavas phase. The general formula ZrMn _a V
_b M _x Cr _y Ni _z and _{Zr 1.2-w Ti w Mn a} V b M x Cr y
In Ni _z , it is preferable that 1.2 ≦ x + z.

In the above, it is preferable that M is Co. Further, it is preferable that homogenizing heat treatment is performed for at least 1 hour in a vacuum at 1000 to 1300 ° C. or in an inert gas atmosphere after alloy production.
The hydrogen storage alloy electrode of the present invention is composed of the above hydrogen storage alloy or a hydride thereof.

[0008]

The hydrogen storage alloy of the present invention is an improvement over the conventional Zr-based Lavas phase alloy or Zr-Ti-based Lavas phase alloy. That is, in the hydrogen storage alloys of claims 1 and 2, the amount of Mn contained in the alloy is reduced, so that the elution of Mn into the alkaline electrolyte is reduced as compared with the conventional alloy. In addition, claim 4
The hydrogen storage alloys of Nos. 5 and 5 have a higher Mn content in the alkaline electrolyte than the conventional alloys by increasing the Cr content.
The amount of elution of is reduced.

1) Zr or Zr-Ti-based Lavas alloy with reduced Mn content: If the Mn content a is made smaller than 0.4, the elution amount of Mn is greatly reduced and a short circuit hardly occurs. However, when the Mn amount a is smaller than 0.1, the electrode activity (activity for electrochemical hydrogen storage-release) is significantly reduced, and the discharge capacity is very small. Therefore, the range of Mn amount a is 0.1 ≦ a <0.4.
Is appropriate. However, by reducing the Mn content, M
Even if the elution of n is suppressed, the elution amount is not zero, so that a short circuit will eventually occur. Therefore, when a sealed battery is constructed, it is necessary to include Cr as an alloy component in order to prevent a short circuit even if left at 65 ° C. for 60 days. C
r forms a passive film in an alkaline electrolyte,
It has the effect of suppressing the elution of Mn. However, forming a passive film in an alkaline electrolyte is
Since the charge / discharge reaction is hindered, the Cr amount y needs to be 0.2 or less because the Mn amount is reduced. Therefore, the range of Cr amount y is 0 <y ≦ 0.2
Is good. As described above, the range of Mn amount a is 0.1 ≦ a <
0.4 and the Cr amount y range is 0 <y ≦ 0.2
By this, short circuit can be prevented even at high temperature storage for 60 days.

The composition range other than Mn and Cr is determined from the viewpoint of maintaining the high capacity of conventional alloys. 1-1) formula _{ZrMn a V b M x Cr y} Zr -based alloy represented by Ni _z: V is a high affinity for hydrogen element, hydrogen storage - contributing to increased emissions. However, if the V amount b is less than 0.05, the effect of V does not appear. Also,
When it exceeds 0.3, the homogeneity of the alloy is deteriorated and conversely the hydrogen storage-release amount is reduced. Therefore, the V amount b is 0.05
≦ b ≦ 0.3 is preferable. Ni contributes to the improvement of electrode activity. However, if the Ni content z is less than 1.0, substantially no electrode activity can be obtained. However, when the amount of Ni increases, the hydrogen storage-release amount decreases. Since the flatness of the plateau region in the PCT curve is improved and the amount of Mn contributing to the increase of the discharge capacity is small, it is necessary to suppress the Ni amount z to 1.3 or less to secure the hydrogen storage-release amount. Therefore,
Appropriate Ni content z is 1.0 ≦ z ≦ 1.3.

Further, M (Al, Co, Fe, Cu, Z
n) is also an element that improves the electrode activity. Since the electrode activity is lowered due to the small amount of Mn, M is required for the alloy composition. This is because if an attempt is made to compensate for the lowered electrode activity by increasing the Ni amount, the hydrogen storage-release amount will decrease, and as a result the discharge capacity will decrease.
However, when the M content x exceeds 0.2, the homogeneity of the alloy is reduced, the plateau pressure is increased, and the discharge capacity is reduced. Therefore, 0 <x ≦ 0.2 is appropriate. Ratio of number of B site atoms to number of A site atoms (a + b + x + y +
When z) is 2.0 or more, the homogeneity of the alloy is greatly improved and the discharge capacity is increased. However, when it is larger than 2.4, the plateau pressure rises because the crystal lattice constant becomes very small, and the discharge capacity decreases. Therefore,
It is suitable that 2.0 ≦ a + b + x + y + z ≦ 2.4.

1-2) General formula Zr _1.1-w Ti _w Mn _a V _b M
Zr-Ti-based alloys represented by _x Cr _y Ni _z: In this alloy, Ti is an element occupying the A site as with Zr. Since the atomic radius of Ti is smaller than that of Zr, the crystal lattice constant becomes very small when the amount of Ti is larger than the amount of Zr, so that the hydrogen storage-release amount is greatly reduced. Therefore, the Ti amount w needs to be equal to or less than the Zr amount. The inclusion of Ti lowers the crystal lattice constant as compared with the case of Zr base. Therefore, in the case of a Zr-Ti-based alloy, the V effect does not appear unless the V amount b is 0.1 or more, but the homogeneity of the alloy is not impaired if the V amount is up to 0.4. Therefore, the V amount b is appropriately 0.1 ≦ b ≦ 0.4. Further, since the corrosion resistant oxide film is formed by containing Ti, the electrode activity is slightly lowered. Therefore, the Ni amount z needs to be 1.1 or more. However, since Ti improves the flatness of the plateau region of the PCT curve, if the Ni amount z is 1.4 or less, the hydrogen storage-release amount can be secured. Therefore, the Ni content z is 1.1 ≦ z ≦ 1.
4 is appropriate.

M is the same as in the case of the Zr-based alloy described above. Regarding the ratio of the number of B-site atoms to the number of A-site atoms (a + b + x + y + z / 1.1),
Since it contains Ti, when it is larger than 2.2, the crystal lattice constant lowers, so 2.2 or less is preferable. The lower limit is 1.7
Since the alloy homogeneity is not significantly reduced even when the temperature is lowered to 0.7, the range is 1.7 ≦ (a + b + x + y + z) /
1.1 ≦ 2.2 is suitable. Regarding the above two alloys, when the amount x + z, which is the sum of the amount of M and the amount of Ni, is 1.3 or more, the electrode activity becomes particularly large and the discharge capacity also becomes large. Therefore, it is preferable that 1.3 ≦ x + z.

2) Zr or Zr-Ti-based Larvous phase alloys with increased Cr content:
Since Cr forms a passive film in an alkaline electrolyte,
When the Cr amount y is 0.2 or more, the elution of Mn is suppressed,
Short circuit is less likely to occur. However, since Cr inhibits the charge / discharge reaction, when the Cr amount y exceeds 0.5, the electrode activity is greatly reduced and the discharge capacity is very small. Therefore, the range of the Cr amount y is appropriately 0.2 ≦ y ≦ 0.5. However, even if the Cr amount is increased, if the Mn amount a exceeds 0.8, the elution of Mn becomes severe and it becomes difficult to suppress the elution. Further, Cr has an adverse effect on the flatness of the plateau region in the PCT curve, so a Mn amount of 0.4 or more is necessary. Therefore, the Mn amount a is 0.4 ≦ a ≦
0.8 is suitable. As described above, when the range of the Mn amount a is 0.4 ≦ a ≦ 0.8 and the range of the Cr amount y is 0.2 ≦ y ≦ 0.5, the high temperature storage is performed for 60 days. Can also prevent a short circuit.

The composition range other than Mn and Cr is determined from the viewpoint of maintaining the high capacity of conventional alloys. 2-1) In formula _{ZrMn a V b M x Cr y} Zr -based alloy represented by Ni _z: V is a high affinity for hydrogen element, hydrogen storage - contributing to increased emissions. However, if the V amount b is less than 0.05, the effect of V does not appear, and if it exceeds 0.3, the homogeneity of the alloy deteriorates and conversely the hydrogen storage-release amount decreases. Therefore, the V amount b is 0.05 ≦ b ≦ 0.
3 is good. Ni contributes to the improvement of electrode activity. But,
When the Ni content z is less than 1.0, the electrochemical activity is poor and the discharge capacity becomes small. However, when the amount of Ni increases, the hydrogen storage-release amount decreases. Since the amount of Cr that reduces the discharge capacity is large, it is necessary to suppress the Ni amount z to 1.3 or less to secure the hydrogen storage-release amount. Therefore,
Appropriate Ni content z is 1.0 ≦ z ≦ 1.3.

Further, M (Al, Co, Fe, Cu, Z
n) is also an element that improves the electrode activity. Since the electrode activity is reduced due to the large amount of Cr, M is required for the alloy composition. This is because if an attempt is made to compensate for the lowered electrode activity by increasing the Ni amount, the hydrogen storage-release amount will decrease, resulting in a decrease in discharge capacity. However, when the M content x exceeds 0.2, the homogeneity of the alloy is reduced, the plateau pressure is increased, and the discharge capacity is reduced.
Therefore, 0 <x ≦ 0.2 is appropriate. When the ratio of the number of B-site atoms to the number of A-site atoms (a + b + x + y + z) is 2.0 or more, the homogeneity of the alloy is greatly improved and the discharge capacity is increased, but when it is more than 2.4, the crystal lattice constant is very small. Therefore, the plateau pressure rises and the discharge capacity decreases. Therefore, 2.0 ≦ a + b + x
Suitably + y + z ≦ 2.4.

2-2) General formula Zr _1.2-w Ti _w Mn _a V _b M
Zr-Ti-based alloys represented by _x Cr _y Ni _z: In this alloy, Ti is an element occupying the A site as with Zr. Since the atomic radius of Ti is smaller than that of Zr, the crystal lattice constant becomes very small when the amount of Ti is larger than the amount of Zr, so that the hydrogen storage-release amount is greatly reduced. Therefore, the Ti amount w needs to be equal to or less than the Zr amount. The inclusion of Ti lowers the crystal lattice constant as compared with the case of Zr base. Therefore, in the case of a Zr-Ti-based alloy, the V effect does not appear unless the V amount b is 0.1 or more, but the homogeneity of the alloy is not impaired if the V amount is up to 0.4. Therefore, the V amount b is appropriately 0.1 ≦ b ≦ 0.4. Further, since the corrosion resistant oxide film is formed by containing Ti, the electrode activity is slightly lowered. Therefore, the Ni amount z needs to be 1.1 or more. However, since Ti improves the flatness of the plateau region of the PCT curve, if the Ni amount z is 1.4 or less, the hydrogen storage-release amount can be secured. Therefore, the Ni content z is 1.1 ≦ z ≦ 1.
4 is appropriate.

M is the same as in the case of the Zr-based alloy described above. Regarding the ratio of the number of B-site atoms to the number of A-site atoms (a + b + x + y + z / 1.2),
Since the content of Ti is larger than 2.2, the crystal lattice constant decreases, so 2.2 or less is preferable. The lower limit is 1.7
Even if the alloy is lowered to a low temperature, the homogeneity of the alloy is not significantly reduced.
Therefore, 1.7 ≦ (a + b + x + y + z) /1.2≦
2.2 is suitable. Regarding the above two alloys, when the amount x + z, which is the sum of the amount of M and the amount of Ni, is 1.2 or more, the electrode activity becomes particularly large and the discharge capacity also becomes large. Therefore, it is preferable that 1.2 ≦ x + z.

In each of the above alloys, Co is particularly rich in the electrode activity among the five elements of M, so that the discharge capacity becomes particularly large by including Co in the alloy composition. Therefore, in any of the above alloys, it is desirable to include Co as M. Furthermore, in any of the above alloys, homogenization heat treatment is performed after the alloy is manufactured, so that the homogeneity and crystallinity of the alloy are improved, so that the discharge capacity becomes particularly large. However, if the heat treatment temperature is lower than 1000 ° C., the heat treatment has no effect. On the other hand, if the temperature is higher than 1300 ° C., a large amount of Mn is evaporated and the alloy composition is largely deviated, so that the discharge capacity is decreased. If the heat treatment time is shorter than 1 hour, the effect of heat treatment does not appear. Further, in order to prevent the alloy from being oxidized, the heat treatment is preferably performed in vacuum or in an inert gas atmosphere. Therefore, after alloy production, 1000 to 130
The homogenizing heat treatment is preferably performed for at least 1 hour in a vacuum at 0 ° C. or in an inert gas atmosphere.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. Example 1 Commercially available Zr, Mn, V, Cr, Ni, A
Alloys having the compositions shown in Tables 1 and 2 were prepared by heating and melting the metals of 1, 1, Co, Fe, Cu, and Zn as raw materials in an arc melting furnace in an argon atmosphere. Next, heat treatment was performed in vacuum at 1100 ° C. for 12 hours to obtain an alloy sample.

[0021]

[Table 1]

[0022]

[Table 2]

Sample No. 1 to 9 are comparative examples, sample N
o. 10 to 25 are some examples of the hydrogen storage alloy of the present invention. First, the sample No. For the alloys 1 to 25, a single cell test was conducted in order to evaluate the electrode characteristics as a negative electrode for an alkaline storage battery by an electrochemical charge / discharge reaction. The alloy was pulverized to a particle size of 200 mesh or less, 1 g of this alloy powder, 3 g of carbonyl nickel powder as a conductive agent and 0.12 g of polyethylene fine powder as a binder were thoroughly mixed and stirred, and the diameter was obtained by pressing. It was molded into a disc shape having a thickness of 24.5 mm and a thickness of 2.5 mm. This was heated in vacuum at 130 ° C. for 1 hour to melt the binder to obtain a hydrogen storage alloy electrode. A nickel wire lead was attached to this hydrogen storage alloy electrode to form a negative electrode. A battery was constructed by using a sintered nickel electrode having an excessive capacity as a positive electrode, a polyamide nonwoven fabric as a separator, and an aqueous potassium hydroxide solution having a specific gravity of 1.30 as an electrolyte. A battery with each hydrogen storage alloy electrode as a negative electrode was heated at 25 ° C. to 100 m per 1 g of hydrogen storage alloy.
The battery was charged with A for 5 hours, and similarly, charging / discharging was carried out by discharging 50 mA per 1 g of the alloy to a final voltage of 0.8 V, and the discharge capacity in each cycle was measured.

Sample No. The discharge capacities of Nos. 1, 3 to 6, 8 and 9 were small and were 220 to 280 mAh / g. Sample No. Since Nos. 3, 4 and 9 had a small hydrogen storage amount, the discharge capacity was also small. Sample No. 1,5 is M for alloy
n, M (Al, Co, Fe, Cu, Zn) is not included, so sample No. Since sample No. 6 has a large amount of Cr, sample No.
It is considered that since No. 8 had a small amount of Ni, the electrode activity (activity for electrochemical hydrogen storage-release) was small, and the discharge capacity was reduced. For these, sample N
o. 2,7,10-25 are all 340-380m
The discharge capacity was Ah / g. That is, the alloy No. It was found that 10 to 25 maintain the high capacity of the conventional alloy. Among them, alloy No. containing Co. 1
2 to 16, 22, and 23 all showed a discharge capacity of 360 mAh / g or more. From this fact, Co
It was also found that a particularly large discharge capacity can be obtained by including.

Next, using these hydrogen storage alloys, a sealed nickel-hydrogen storage battery was prepared by the following method. Sample No. shown in Table 1 and Table 2 1-25
Alloy is crushed to 300 mesh or less and mixed with a dilute aqueous solution of carboxymethyl cellulose to form a paste, which has an average pore size of 150 microns as an electrode support, a porosity of 95%, and a thickness of 1.0 mm of nickel foam. The sheet was filled. This was dried at 120 ° C., pressed by a roller press, and the surface thereof was coated with a fluororesin powder to obtain a hydrogen storage alloy electrode. Each of these electrodes has a width of 3.3 cm, a length of 21 cm, and a thickness of 0.4.
The lead plate was adjusted to 0 mm, and the lead plates were attached at two predetermined places. Then, it was spirally wound in combination with a positive electrode and a separator having a capacity of 3.0 Ah, and housed in an SC size battery case. The positive electrode was a known foaming nickel electrode, and its size was 3.3 cm in width and 18 cm in length. Lead plates were also attached to the positive electrode at two positions. The separator used was a polypropylene nonwoven fabric provided with hydrophilicity, and the electrolyte used was a solution prepared by dissolving 30 g / l of lithium hydroxide in an aqueous solution of potassium hydroxide having a specific gravity of 1.20. The opening of the battery case was sealed to form a sealed battery.
The battery thus produced was measured at 45 ° C. for 0.
Charge to 150% at 5C (2 hour rate), then 0.2C (5
Charge and discharge that discharges to a final voltage of 1.0 V at a time rate of 20
It was cycled and then left in an atmosphere of 65 ° C.

FIG. 1 shows the voltage change of each battery during storage at 65 ° C. The numbers in the figure indicate the sample Nos. In Tables 1 and 2. Is consistent with Sample No. The batteries using the alloys of Nos. 2 and 3 as the negative electrode were stored for 40 days, and the sample No. For the battery using No. 7, the battery voltage drastically dropped after each storage period of 30 days. Sample No. Sample No. 2 has a large amount of Mn with respect to the amount of Cr and therefore lacks the ability to suppress the elution of Mn. 7
It is considered that, since Cr did not contain Cr, the elution of Mn could not be suppressed. In addition, the sample No.
In No. 3, it is considered that the elution of V caused the short circuit due to the large amount of V. For these, the sample No. 1,4 ~
6,8 to 25, the Mn content is less than 0.4, and Cr
As a result of the inclusion of
It was found that the battery voltage drop was very small even on day storage. In addition, the sample N containing a small amount of Mn and containing Cr
o. It was found that 1,4 to 6 and 8 to 25 can maintain stable performance even after 300 cycles. As described above, when the results of the single cell test and the high temperature storage test are combined, the alloy No. It was found that Nos. 10 to 25 maintained the high capacity of the conventional alloy, and the drop in battery voltage was very small even after 60 days of high temperature storage.

Example 2 Commercially available Zr, Ti, Mn,
Using V, Cr, Ni, Al, Co, Fe, Cu, and Zn as raw materials, the materials are melted by heating in an arc melting furnace in an argon atmosphere to produce alloys having the compositions shown in Tables 3 and 4. did. Then, in vacuum, 1100
It heat-processed at 12 degreeC for 12 hours, and it was set as the alloy sample.

[0028]

[Table 3]

[0029]

[Table 4]

Sample No. Sample Nos. 26 to 35 are comparative examples. 36 to 55 are some examples of the hydrogen storage alloy of the present invention. First, as in Example 1, sample Nos. The alloys of Nos. 26 to 55 were subjected to a unit cell test in order to evaluate the electrode characteristics as a negative electrode for an alkaline storage battery by an electrochemical charge / discharge reaction. The test method is the same as in Example 1. Sample No. 26, 28-31, 33
~ 35 has a small discharge capacity and is 230 to 300 mAh /
g. Sample No. Nos. 28, 29, 34, and 35 had a small hydrogen storage capacity, and thus had a small discharge capacity.
In addition, the sample No. 26 and 30 are alloy components with M
n, M (Al, Co, Fe, Cu, Zn) is not included, so sample No. No. 31 has a large amount of Cr, and sample N
o. It is considered that since 33 had a small amount of Ni, the electrode activity was low and the discharge capacity was reduced. For these, the sample No. 27, 32, 36 to 55 all showed a discharge capacity of 340 to 380 mAh / g. That is, the alloy No. It was found that 36 to 55 maintained the high capacity of the conventional alloy. Among them, alloy No. containing Co. 40 to 45, 52, 53 are all 3
The discharge capacity was 60 mAh / g or more. From this, it was also found that a particularly large discharge capacity can be obtained by including Co in the alloy component.

Next, the sample Nos. Shown in Tables 3 and 4 were used. 26 ~
Using the alloy of No. 55, a sealed nickel-hydrogen storage battery was produced in the same manner as in Example 1, and at 45 ° C., 0.5
The battery was charged to 150% at C (2 hour rate) and discharged and discharged at a final voltage of 1.0 V at 0.2 C (5 hour rate) for 20 cycles, and then left at 65 ° C. FIG. 2 shows changes in the voltage of each battery during storage. The numbers in the figure are the sample numbers of Tables 3 and 4. Is consistent with Sample No. 27,
Sample No. 28 has a storage period of 40 days. 32 is retention period 30
After each day, the battery voltage dropped sharply. Sample No. No. 27 has a large Mn content relative to the Cr content, so Mn
Since the elution suppressing force was insufficient, the sample No. It is considered that since 32 did not contain Cr, the elution of Mn could not be suppressed. In addition, the sample No. In No. 28, it is considered that the elution of V caused the short circuit due to the large amount of V. For these, the sample No. 26,29 to 31,3
It was found that 3 to 55, in which the amount of Mn was less than 0.4 and also contained Cr, had a large inhibitory effect on Mn elution and showed a very small decrease in battery voltage even after storage for 60 days. In addition, the sample No. containing a small amount of Mn and containing Cr.
It was found that 26, 29 to 31, 33 to 55 can maintain stable performance even after 300 cycles. As described above, when the results of the single cell test and the high temperature storage test are combined, the alloy No. It was found that Nos. 36 to 55 maintained the high capacity of the conventional alloy, and the decrease in battery voltage was very small even after 60 days of high temperature storage.

Example 3 Commercially available Zr, Mn, V, C
Alloys having the compositions shown in Tables 5 and 6 were prepared by heating and melting the metals of r, Ni, Al, Co, Fe, Cu, and Zn as raw materials in an arc melting furnace in an argon atmosphere. However, if the Mn content is 0.8 or more,
When manufactured in an arc furnace, a large amount of Mn evaporates and it is difficult to obtain the target alloy. Therefore, it was manufactured in an induction heating furnace. Next, heat treatment was performed in vacuum at 1100 ° C. for 12 hours to obtain an alloy sample.

[0033]

[Table 5]

[0034]

[Table 6]

Sample No. 56 to 64 are comparative examples, and sample No. 65 to 82 are some examples of the hydrogen storage alloy of the present invention. First, as in Example 1, the sample Nos. The alloys of Nos. 56 to 82 were subjected to a single cell test in order to evaluate the electrode characteristics as a negative electrode for an alkaline storage battery by an electrochemical charge / discharge reaction. The test method is the same as in Example 1. Sample No. 56-61, 63, 64
Had a small discharge capacity of 200 to 280 mAh / g. Sample No. In sample No. 57, since the amount of Mn was large, the deterioration of the discharge capacity due to the cycle was large. 58, 59,
In No. 64, since the hydrogen storage amount itself is small, the discharge capacity is also small. In addition, the sample No. 56 and 63 are each Mn
Amount and Ni amount are small, sample No. No. 60 does not include M (Al, Co, Fe, Cu, Zn) in the alloy composition,
Sample No. It is considered that since 61 has a large amount of Cr, the electrode activity is low and the discharge capacity is reduced.
For these, the sample No. 62, 65-82 all showed the discharge capacity of 340-380 mAh / g. That is, the alloy No. It was found that 65 to 82 maintain the high capacity of the conventional alloy. Among them, C
Alloy No. including o. 68 to 72, 79 and 80 all showed a discharge capacity of 360 mAh / g or more. From this, it was also found that a particularly large discharge capacity can be obtained by including Co in the alloy component.

Next, the sample Nos. Shown in Tables 5 and 6 were used. 56-
Using the alloy of No. 82, a sealed nickel-hydrogen storage battery was produced in the same manner as in Example 1 and at 45 ° C., 0.5
The battery was charged to 150% at C (2 hour rate) and discharged and discharged at a final voltage of 1.0 V at 0.2 C (5 hour rate) for 20 cycles, and then left at 65 ° C. FIG. 3 shows changes in the voltage of each battery during storage. The numbers in the figure indicate the sample Nos. In Tables 5 and 6. Is consistent with Sample No. Sample No. 57 has a storage period of 20 days and a sample No. 57. Sample No. 62 has a storage period of 30 days. In No. 58, the battery voltage drastically dropped after each storage period of 40 days. Sample No. No. 57 has a large Mn content, and sample No. It is considered that since 62 did not contain Cr, the elution of Mn could not be suppressed. In addition, the sample No. 58 has a large amount of V, so V
It is considered that the elution of the water was the cause of the short circuit. For these, the sample No. 56, 59-61, 63-82
It was found that since the alloy contains a large amount of Cr, it has a large inhibitory effect on Mn elution and the battery voltage drop is very small even after storage for 60 days. In addition, the sample No. 5
It was found that 6, 59 to 61 and 63 to 82 can maintain stable performance even after 300 cycles. As described above, when the results of the single cell test and the high temperature storage test are combined, the alloy No. It was found that Nos. 65 to 82 maintained the high capacity of the conventional alloys, and the drop in battery voltage was very small even after 60 days of high temperature storage.

Example 4 Commercially available Zr, Ti, Mn,
Using V, Cr, Ni, Al, Co, Fe, Cu, and Zn as raw materials, the alloys having the compositions shown in Tables 7 and 8 were prepared by heating and melting in an arc melting furnace in an argon atmosphere. . However, when the amount of Mn is 0.8 or more, a large amount of Mn evaporates when it is manufactured in an arc furnace, and it is difficult to obtain the target alloy, so it was manufactured in an induction heating furnace. Then, heat treatment in vacuum at 1100 ° C. for 12 hours,
An alloy sample was used.

[0038]

[Table 7]

[0039]

[Table 8]

Sample No. 83 to 92 are comparative examples, and sample No. 93 to 112 are some examples of the hydrogen storage alloy of the present invention. First, as in Example 1, Tables 7 and 8
Sample No. With respect to the alloys Nos. 83 to 112, a unit cell test was conducted in order to evaluate the electrode characteristics as a negative electrode for an alkaline storage battery by an electrochemical charge / discharge reaction. The test method is the same as in Example 1. Sample No. 83-88, 90-
92 has a small discharge capacity and is 220 to 280 mAh / g.
Met. Sample No. Sample No. 84 has a large amount of Mn, so that the discharge capacity is greatly deteriorated due to the cycle. 85,8
6, 91, and 92, the hydrogen storage amount itself was small, so the discharge capacity was also small. In addition, the sample No. Nos. 83 and 90 have small amounts of Mn and Ni, respectively. No. 87 does not include M (Al, Co, Fe, Cu, Zn) in the alloy components, and Sample No. It is considered that since 88 had a large amount of Cr, the electrode activity was low and the discharge capacity was reduced. For these, the sample No. 89, 93-
112 all showed a discharge capacity of 340 to 380 mAh / g. That is, the alloy No. 93-11
No. 2 was found to maintain the high capacity of the conventional alloy. Among them, alloy No. containing Co. 97-102,1
Nos. 09 and 110 each showed a discharge capacity of 360 mAh / g or more. From this, it was also found that a particularly large discharge capacity can be obtained by including Co in the alloy composition.

Next, the sample Nos. Shown in Tables 7 and 8 were used. 83 ~
Using the alloy of No. 112, a sealed nickel-hydrogen storage battery was produced in the same manner as in Example 1, and at 45 ° C.
Charge to 150% at 5C (2 hour rate), then 0.2C (5
The charging / discharging was carried out for 20 cycles at a final voltage of 1.0 V at a rate of time), and then left at 65 ° C. FIG.
Shows the voltage change of each battery during storage. The numbers in the figure indicate the sample numbers in Tables 7 and 8. Is consistent with Sample N
o. Sample No. 84 has a storage period of 20 days. 89 is a storage period of 30 days, sample No. The battery voltage of 85 dropped sharply after 40 days of storage. Sample No. No. 84 has a large amount of Mn, and sample No. It is considered that since 89 did not contain Cr, the elution of Mn could not be suppressed. In addition, the sample No. No. 85 is considered to have caused the short circuit due to the elution of V due to the large amount of V. For these, the sample No. 83,86-88,9
It was found that since 0 to 112 contain a large amount of Cr, the ability to suppress Mn elution is large, and the decrease in battery voltage is very small even after storage for 60 days. In addition, the sample No. It was found that 83, 86 to 88, 90 to 112 can maintain stable performance even after 300 cycles. As described above, when the results of the single cell test and the high temperature storage test are combined, the alloy No. 93-112
Maintains the high capacity of conventional alloys and preserves it at high temperatures.
It was found that the battery voltage drop was very small even on a day.

[0042]

As described above, the hydrogen storage alloy of the present invention has a M content higher than that of conventional hydrogen storage alloys in alkaline electrolyte.
The elution of n is reduced. Therefore, the alkaline storage battery using this alloy as the negative electrode can have further improved high-temperature storage characteristics and excellent cycle life characteristics as compared with conventional batteries.

[Brief description of drawings]

FIG. 1 is a diagram comparing changes in voltage during high-temperature storage of batteries using alloy negative electrodes of Examples of the present invention and Comparative Examples.

FIG. 2 is a diagram comparing changes in voltage during high-temperature storage of batteries using alloy negative electrodes of Examples of the present invention and Comparative Examples.

FIG. 3 is a diagram comparing changes in voltage during high-temperature storage of batteries using the alloy negative electrodes of Examples of the present invention and Comparative Examples.

FIG. 4 is a diagram comparing changes in voltage during high-temperature storage of batteries using the alloy negative electrodes of Examples of the present invention and Comparative Examples.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoichiro Tsuji 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. In the company

Claims (9)

[Claims] 1. A general formula _{ZrMn a V b M x Cr y} Ni z ( however, M is at least one element selected Al, Co, Fe, from the group consisting of Cu and Zn, 0.1 ≦
a <0.4, 0.05 ≦ b ≦ 0.3, 0 <x ≦ 0.2,
0 <y ≦ 0.2, 1.0 ≦ z ≦ 1.3, and 2.0 ≦ a
+ B + x + y + z ≦ 2.4), and the main component of the alloy phase is a C15 (MgCu ₂ ) type Larvus phase. 2. A general formula _{Zr 1.1-w Ti w Mn a} V b M x Cr y
Ni _z (where M is Al, Co, Fe, Cu and Z
at least one element selected from the group consisting of n, 0 <w ≦ 0.5, 0.1 ≦ a <0.4, 0.1 ≦ b
≦ 0.4, 0 <x ≦ 0.2, 0 <y ≦ 0.2, 1.1 ≦
z ≦ 1.4 and 1.7 ≦ (a + b + x + y + z) /
1.1 ≦ 2.2) and the main component of the alloy phase is C15
A hydrogen storage alloy that is a (MgCu ₂ ) type Lavas phase. 3. The method according to claim 1, wherein 1.3 ≦ x + z.
The hydrogen storage alloy described. Wherein the general formula _{ZrMn a V b M x Cr y} Ni z ( however, M is at least one element selected Al, Co, Fe, from the group consisting of Cu and Zn, 0.4 ≦
a ≦ 0.8, 0.05 ≦ b ≦ 0.3, 0 <x ≦ 0.2,
0.2 ≦ y ≦ 0.5, 1.0 ≦ z ≦ 1.3, and 2.0
≦ a + b + x + y + z ≦ 2.4), and the main component of the alloy phase is a C15 (MgCu ₂ ) type Larvus phase, a hydrogen storage alloy. 5. The general formula Zr _1.2-w Ti _w Mn _a V _b M _x Cr _y.
Ni _z (where M is Al, Co, Fe, Cu and Z
at least one element selected from the group consisting of n, 0 <w ≦ 0.6, 0.4 ≦ a ≦ 0.8, 0.1 ≦ b
≦ 0.4, 0 <x ≦ 0.2, 0.2 ≦ y ≦ 0.5, 1.
1 ≦ z ≦ 1.4 and 1.7 ≦ (a + b + x + y + z)
/1.2≦2.2), and the main component of the alloy phase is C15
A hydrogen storage alloy that is a (MgCu ₂ ) type Lavas phase. 6. The method according to claim 4, wherein 1.2 ≦ x + z.
The hydrogen storage alloy described. 7. The hydrogen storage alloy according to claim 1, wherein Co is contained as M. 8. After the alloy is produced, at least 1 is applied in a vacuum at 1000 to 1300 ° C. or in an inert gas atmosphere.
The hydrogen storage alloy according to any one of claims 1 to 7, which has been subjected to a homogenizing heat treatment for a time. 9. A hydrogen storage alloy electrode comprising the hydrogen storage alloy according to claim 1 or a hydride thereof.