JPH0639644B2 - Hydrogen storage N-below i-Zr alloy and sealed Ni-hydrogen storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a MgZn ₂ type crystal structure, that is, hexagonal C
The present invention relates to a hydrogen storage Ni-Zr alloy having a 14-type crystal structure, and a sealed Ni-hydrogen storage battery using this hydrogen storage Ni-Zr alloy as a negative electrode active material.

[Conventional technology]

Generally, a sealed Ni-hydrogen storage battery is composed of a negative electrode using a hydrogen storage alloy as an active material, a Ni positive electrode, a separator and an alkaline electrolyte, and a hydrogen storage alloy constituting the negative electrode includes a) Hydrogen storage / release capacity is high near room temperature.

(b) The equilibrium hydrogen dissociation pressure corresponding to the plateau pressure at a temperature near room temperature in the PCT curve is relatively low (5 atm or less).

(c) Corrosion resistance and durability (deterioration resistance) in alkaline electrolyte.

(d) Hydrogen oxidization capacity (catalysis) is large.

(e) It is difficult for pulverization to occur due to repeated storage and release of hydrogen.

(f) No (low) pollution.

(g) Low cost.

It is desired to have the above properties (a) to (g), and further, a sealed Ni-hydrogen storage battery using a hydrogen storage alloy having such properties as an active material of a negative electrode has a large discharge capacity, It is also well known that favorable characteristics such as long charge / discharge cycle life, excellent rapid charge / discharge characteristics, and low self-discharge will be exhibited.

Therefore, particularly, a hydrogen storage alloy suitable for use as an active material constituting a negative electrode of a sealed Ni-hydrogen storage battery has been actively developed, and for example, MgZn ₂ type crystal described in JP-A-61-45563. A number of hydrogen storage alloys have been proposed, including a hydrogen storage alloy having a structure, that is, a hexagonal C14 type crystal structure.

[Problems to be Solved by the Invention]

However, none of the hydrogen storage alloys that have already been proposed satisfy all of the above properties required when used as a negative electrode active material of a sealed Ni-hydrogen storage battery, and further development is desired. The current situation is that it is rare.

[Means for Solving the Problems]

Therefore, the present inventors conducted research to develop a hydrogen storage alloy that is particularly suitable for use as a negative electrode active material of a sealed Ni-hydrogen storage battery from the above viewpoints, and as a result, % Represents% by weight), Ti-5 to 20%, Zr: 10 to 37%, Mn: 5 to 30%, W: 0.01 to 15%, Fe: 1 to 30%, and if necessary. Depending on: Cr: 0.05-6% and Al: 0.01-5%, one of
A hydrogen-storing Ni-Zr alloy having a composition containing Ni or Z, and the balance being Ni and inevitable impurities, has a MgZn ₂ type crystal structure (hexagonal C 14 type crystal structure), and is a sealed Ni-hydrogen. The above required when used as a negative electrode active material of a storage battery
A sealed Ni-hydrogen storage battery, which has the properties (a) to (g) in a sufficiently satisfied state and therefore uses this as a negative electrode active material, has a large energy density and electric capacity and has a long cycle life. In addition to the above, we have obtained the knowledge that self-discharge is reduced, and high-rate charge / discharge characteristics are also excellent, and excellent performance is exhibited together with no pollution and low cost.

The present invention has been made based on the above findings, Ti-5 to 20%, Zr: 10 to 37%, Mn: 5 to 30%, W: 0.01 to 15%, Fe: 1 to 30%, MgZn ₂ having a composition containing Cr, 0.05 to 6% and Al: 0.01 to 5%, one or two of: and the balance Ni and inevitable impurities. Characterized by a hydrogen-storing Ni-Zr-based alloy having a C-type crystal structure (hexagonal C14-type crystal structure) and a sealed Ni-H2 battery using the hydrogen-storing Ni-Zr-based alloy as a negative electrode active material Is.

Next, the reason why the component composition of the hydrogen storage Ni—Zr alloy of the present invention is limited as described above will be explained.

(a) Ti and Zr These components have the effect of lowering the equilibrium hydrogen dissociation pressure (plateau pressure) at room temperature to, for example, 5 atm or less, while coexisting to provide the alloy with desirable hydrogen storage / release characteristics. However, if their contents are less than 5% of Ti and less than 10% of Zr, respectively, the desired effects cannot be obtained. On the other hand, if the content of Ti exceeds 20%, the equilibrium hydrogen dissociation pressure is, for example, 5 atm or more. The high hydrogen dissociation pressure is required to secure a large discharge capacity, which is unfavorable as a storage battery.
Also, if the Zr content exceeds 37%, there is no problem in the dependence of the discharge capacity on the hydrogen dissociation pressure, but the hydrogen storage / release capacity will decrease.
i: 5 to 20%, Zr: 10 to 37%.

(b) Mn The Mn component not only improves hydrogen storage / release capacity and corrosion resistance and durability of the alloy in alkaline electrolyte, but also suppresses self-discharge during practical use as a negative electrode active material for storage batteries. There is an action, but if the content is less than 5%, the desired effect cannot be obtained on the other hand, while the content is
If it exceeds 30%, the hydrogen storage / release characteristics will be impaired, so the content was defined as 5-30%.

(c) The WW component has the effect of further improving the corrosion resistance of the alloy in an alkaline electrolyte and also improving the durability, and further suppressing self-discharge during practical use as a negative electrode active material of a storage battery, If the content is less than 0.01%, the desired effect cannot be obtained, while if the content exceeds 15%, the hydrogen storage / release characteristics will be impaired. It was set at ~ 15%.

(d) Fe The Fe component has a function of further stabilizing the hydride and thus contributing to the stabilization of the storage battery performance, and even if it is used as a partial replacement component of Ni, the function and effect brought about by Ni are impaired. Therefore, if the content is less than 1%, the desired effect cannot be obtained, and if the content exceeds 30%, the hydrogen storage capacity decreases. Therefore, the content is defined as 1 to 30%.

(e) Cr and Al These components have a function of further improving the corrosion resistance in an alkaline electrolyte without lowering the hydrogen storage / release capacity, so they are contained as necessary. If the amounts of Cr: less than 0.05% and Al: less than 0.01%, the desired effect of improving corrosion resistance cannot be obtained, while if their contents exceed Cr: 6% and Al: 5%, respectively, the hydrogen storage / release capacity is reduced. Since the content of Cr decreases, the contents are determined to be Cr: 0.05-6% and Al: 0.01-5%, respectively.

Example Next, the hydrogen storage Ni—Zr alloy of the present invention will be specifically described by way of examples.

Using a normal high frequency induction melting furnace, a Ni alloy melt having the composition shown in Table 1 was prepared in an Ar atmosphere, cast into a copper mold to form an ingot, and the ingot was heated in an Ar atmosphere at 900 Annealed at a predetermined temperature within the range of up to 1000 ° C for 5 hours, then coarsely crushed using a jaw crusher to obtain coarse particles with a diameter of 2 mm or less, and further finely crushed with a ball mill to 350 mesh or less. The hydrogen storage alloys 1 to 20 of the present invention, the comparative hydrogen storage alloys 1 to 9 and the conventional hydrogen storage alloys each having the MgZn ₂ type crystal structure were manufactured by changing the grain size.

Then, various powdery hydrogen storage alloys obtained as a result were used as active materials, and first, a 2% aqueous solution of pyrivinyl alcohol (PVA) was added to form a paste, which had a porosity of 95%. Fill a commercially available Ni whisker non-woven fabric, dry it, and pressurize it to obtain a planar dimension of 42 mm x
The thickness is 35 mm and the thickness is 0.60 to 0.65 mm (active material filling amount: about 2.8 g). A Ni thin plate to be a lead is attached by welding to one side of this to manufacture a negative electrode. Two Ni sintered plates were prepared, placed on both sides of the negative electrode, and charged with a 30% KOH aqueous solution to manufacture a sealed Ni-hydrogen storage battery.

The various storage batteries obtained as a result were all open batteries, and the capacity of the negative electrode was made significantly larger than the capacity of the negative electrode so that the capacity of the negative electrode could be measured.

Further, in the above comparative hydrogen storage alloys 1 to 9, the content of the constituent components (marked with * in Table 1) is out of the range of the present invention.

Next, for these various storage batteries, the charge / discharge rate:
0.2C, amount of electricity charged: 130% of negative electrode capacity Charge / discharge test is performed under the conditions
Cycle, 100 cycles, 200 cycles, and
The discharge capacity after 300 cycles was measured, and each of the above powdery hydrogen storage alloys was used as a negative electrode.
In each case, an AA size (capacity: 1000 mAh) sealed Ni-hydrogen storage battery regulated by the positive electrode was assembled, and a self-discharge test was conducted for each, and the results are shown in Table 1.

Furthermore, in detail, the powdery hydrogen storage alloy powder shown in Table 1 is used, the plane size is 90 mm × 40 mm, the thickness: 0.60 ~
As 0.65 mm, capacity: 1450 to 1500 mAh (active material filling amount:
A negative electrode plate was manufactured under the same conditions as the negative electrode plate of the storage battery used in the above charge / discharge test except that the amount was about 6 g), while the positive electrode plate was a Ni whisker nonwoven fabric having a porosity of 95% and nickel hydroxide. [Ni (OH) ₂ ] is filled as an active material,
After drying and pressing, attach the leads,
Planar dimensions: 70 mm x 40 mm, thickness: 0.65 to 0.70 mm (capacity: 1000 to 1050 mAh), and the resulting negative electrode plate and positive electrode plate were spirally wound through a separator. In this state, a sealed Ni-hydrogen storage battery having a structure of being housed in a case (which also serves as a terminal) together with an electrolytic solution was manufactured.

In addition, in the above various sealed Ni-hydrogen storage batteries, the reason why the negative electrode capacity was made larger than the positive electrode capacity was to configure a storage battery of positive electrode law.

In the self-discharge test, first charge at room temperature 0.2C (200mA) for 7 hours, then open the storage battery in the thermostat with the temperature set to 45 ° C (no load on the battery).
The sample was left for 1 week and 2 weeks, taken out, discharged at room temperature for 0.2 C (200 mA), and the residual capacity ratio was determined.

Furthermore, regarding the above various hydrogen storage alloys, in general, H
Using a method called uey test, cut out the test piece from the above ingot and embed it in plastic resin,
After the corroded surface was polished with Emery Paper # 600, put it in an Erlenmeyer flask equipped with a cold finger type condenser, and perform an alkaline electrolyte corrosion test in a boiling 30% KOH aqueous solution for 144 hours. The corrosion weight loss was measured. The results of these measurements are also shown in Table 1.

〔The invention's effect〕

From the results shown in Table 1, the present hydrogen storage alloys 1 to 20
Are both excellent in corrosion resistance to alkaline electrolytes as compared with conventional hydrogen storage alloys, and storage batteries using this as a negative electrode active material are both high-capacity and conventional hydrogen storage alloys. Compared to storage batteries using
In contrast to the preferable result that the capacity decrease when the discharge cycle is repeated is remarkably small, the content of any one of the constituent components falls within the scope of the present invention as seen in Comparative Hydrogen Storage Alloys 1 to 9. If it is out of the range, it is clear that the corrosion resistance to the alkaline electrolyte decreases, and that if it is used as the negative electrode active material of the storage battery, the discharge capacity and self-discharge of the storage battery will tend to deteriorate.

As described above, the hydrogen-absorbing Ni-Zr alloy of the present invention has excellent corrosion resistance to an alkaline electrolyte, and particularly when used as a negative electrode active material of a sealed Ni-hydrogen storage battery, it is required as a negative electrode active material. It has industrially useful characteristics such as self-discharge of the storage battery is significantly reduced and a large discharge capacity is secured over a long cycle life because it has all the characteristics described above in a state of being sufficiently satisfied. Of.

Claims (4)

[Claims] 1. Ti: 5 to 20%, Zr: 10 to 37%, Mn: 5 to 30%, W: 0.01 to 15%, Fe: 1 to 30%, the rest being Ni and inevitable impurities. A hydrogen storage Ni-Zr-based alloy having a MgZn ₂ type crystal structure, characterized in that it has a composition of (at least by weight). 2. Ti: 5 to 20%, Zr: 10 to 37%, Mn: 5 to 30%, W: 0.01 to 15%, Fe: 1 to 30%, and the balance Ni and inevitable impurities. A sealed Ni-hydrogen storage battery using as a negative electrode active material a hydrogen storage Ni-Zr-based alloy having a MgZn ₂ type crystal structure having a composition of (at least by weight). 3. Ti: 5-20%, Zr: 10-37%, Mn: 5-30%, W: 0.01-15%, Fe: 1-30%, and Cr: 0.05-. 6% and Al: 0.01-5%, one of
A hydrogen-storing Ni-Zr-based alloy having a MgZn ₂ type crystal structure, characterized in that the hydrogen-storing Ni-Zr-based alloy has a composition (containing at least wt. 4. Ti: 5-20%, Zr: 10-37%, Mn: 5-30%, W: 0.01-15%, Fe: 1-30%, and Cr: 0.05-. 6% and Al: 0.01-5%, one of
Sealed type using as a negative electrode active material a hydrogen storage Ni—Zr alloy having a MgZn ₂ type crystal structure having a composition of Ni and unavoidable impurities (above wt%) Ni-hydrogen storage battery.