JPH0639646B2 - Hydrogen storage Ni-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, a hexagonal C14 crystal structure.
The present invention relates to a hydrogen storage Ni-Zr type alloy having a type crystal structure, and a sealed Ni-hydrogen storage battery using the hydrogen storage Ni-Zr type 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 the 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-mentioned 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 for 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), Zr: 10 to 37%, Ti: 5 to 25%, Mn: 4 to 20%, W: 0.01 to 13%, V: 0.1 to 15%, Fe: 0.051 to 5%, al: from 0.01 to 4.5%, containing, if necessary, Cr: 0.05 to 6%, containing, hydrogen-absorbing Ni-Zr based alloy having a composition balance being Ni and unavoidable impurities, MgZn ₂ It has a C-type crystal structure (hexagonal C14-type crystal structure) and is required when used as a negative electrode active material of a sealed Ni-hydrogen 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 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 was made based on the above findings, and Zr: 10-37%, Ti: 5-25%, Mn: 4-20%, W: 0.01-13%, V: 0.1-15%, Fe: 0.01~5%, Al: 0.01~4.5 %, contains, further as necessary, Cr: 0.05 to 6%, containing, MgZn ₂ type crystal having the composition balance being Ni and unavoidable impurities It is characterized by a hydrogen-storing Ni-Zr-based alloy having a structure, that is, a hexagonal C14 type crystal structure, and a sealed Ni-hydrogen storage battery using this hydrogen-storing Ni-Zr-based alloy as a negative electrode active material. .

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

(a) Ti and Zr These components have the effect of making the alloy have desirable hydrogen absorption / desorption characteristics in the coexisting state, and lowering the equilibrium hydrogen dissociation pressure (plateau pressure) at room temperature to, for example, 5 atm or less. However, if the contents thereof are respectively Ti: less than 5% and Zr: less than 10%, the desired effect cannot be obtained. On the other hand, if the content of Ti exceeds 25%, the equilibrium hydrogen dissociation pressure is, for example, 5 atm. As a result, the hydrogen dissociation pressure becomes high in order to secure a large discharge capacity, which is unfavorable as a storage battery, and when the Zr content exceeds 37%, the discharge capacity is increased. Although there is no problem with respect to the hydrogen dissociation pressure dependency, the hydrogen storage / desorption ability decreases, so the contents were set to Ti: 5 to 25% and Zr: 10 to 37%, respectively.

(b) Mn Mn component not only improves hydrogen storage / release capacity, but also improves corrosion resistance and durability of the alloy in alkaline electrolyte, and 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 4%, the desired effect cannot be obtained on the above action, while the content is
If it exceeds 20%, the hydrogen storage / release characteristics will be impaired, so the content was defined as 4 to 20%.

(c) In the WW component, the corrosion resistance to the alkaline electrolyte constituting the storage battery is further improved, and the durability is also improved.
Further, it has an effect of suppressing self-discharge in practical use as a negative electrode active material of a storage battery, but if its content is less than 0.01%, the desired effect cannot be obtained, while if its content exceeds 13%. Since the hydrogen absorption / desorption characteristics will be impaired, the content was set to 0.01-13%.

(d) V As described above, in the sealed Ni-hydrogen storage battery, it is desired that the equilibrium hydrogen dissociation pressure at room temperature is not excessively high (for example, 5 atm or less) and the hydrogen storage / release amount is as large as possible. The V component has an action of contributing to such an increase in hydrogen storage / release amount and optimization of the equilibrium hydrogen pressure, but if the content thereof is less than 0.1%, the desired effect cannot be obtained in the above action. If the content exceeds 15%, the equilibrium hydrogen pressure will become too high, and it will dissolve into the electrolyte and promote self-discharge, so the content should be 0.1-15%. I decided.

(e) The Fe Fe component has a function of sizing the formed powder when powdered such as when used as a negative electrode active material of a storage battery, but if the content thereof is less than 0.01%, it is desirable for the above-mentioned action. The effect is not obtained, and on the other hand, if the content exceeds 5%, the corrosion resistance decreases and the self-discharge of the storage battery is promoted. Therefore, the content was set to 0.01 to 5%.

(f) Al The Al component has the effect of further improving the corrosion resistance of the alloy without lowering the hydrogen storage / release capacity and thus further suppressing the self-discharge of the storage battery, but its content is 0.01
When the content is less than 4.5%, the desired effect cannot be obtained, while when the content exceeds 4.5%, the hydrogen storage / release capacity is conspicuously reduced, so the content is 0.01 to 4.
It was set at 5%.

(g) Cr The Cr component has the effect of further improving the corrosion resistance of the alloy, especially in the coexistence with Al, so it is contained if necessary, but if the content is less than 0.05%, the desired corrosion resistance improving effect is obtained. However, if the content exceeds 6%,
Since the hydrogen storage / release capacity decreases, the content thereof is set to 0.05 to 6%.

〔Example〕

Next, the hydrogen storage Ni--Zr alloy of the present invention will be specifically described with reference to examples.

Using a normal high-frequency induction melting furnace, a Ni-Zr 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 then placed in an Ar atmosphere. , Annealed at a predetermined temperature within the range of 900 to 1000 ℃ for 5 hours, then coarsely crushed using a jaw crusher to obtain coarse particles with a diameter of 2 mm or less, and then finely crushed using a ball mill to 350 mesh. The hydrogen storage alloys 1 to 11 of the present invention, the comparative hydrogen storage alloys 1 to 13, and the conventional hydrogen storage alloy, each having the MgZn ₂ type crystal structure, were produced with the following grain sizes.

Then, various powdered hydrogen storage alloys obtained as a result were used as an active material, and first, a 2% aqueous solution of polyvinyl alcohol (PVA) was added to form a paste, which had a porosity of 95%. Fill a commercially available Ni whisker non-woven fabric, dry, pressurize, plane dimension: 42mm 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 serving as a lead is welded 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 could be measured by making the ease of the positive electrode significantly larger than the capacity of the negative electrode.

Further, in the comparative hydrogen storage alloys 1 to 13, the content of the constituent components (marked with * in Table 1) is outside the scope of the present invention.

Next, these various storage batteries were charged / discharged at a charging / discharging rate of 0.2 C and an amount of electricity charged: 130% of the negative electrode capacity.
Perform a discharge test, one charge and discharge as one cycle, after 100 cycles, The discharge capacities after 200 cycles and after 300 cycles were measured, respectively, and further, the above various powdery hydrogen storage N
The i-based alloy was used as the negative electrode, and a sealed type Ni-hydrogen storage battery of AA size (capacity: 1000 mAh) regulated by the positive electrode was assembled in each case, and a self-discharge test was carried out 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 produced 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 hydrated with Ni whisker nonwoven fabric having a porosity of 95%. Nickel [Ni (OH) ₂ ] is filled as an active material, dried, and further pressed, and then a lead is attached, and a shape of plane dimension: 70 mm × 40 mm, thickness: 0.65 to 0.70 mm (capacity: 1000 to 1050 mAh), and the negative electrode plate and positive electrode plate obtained as a result are wound in a spiral shape with a separator between them and housed in a case (also used as a terminal) together with an electrolytic solution. A sealed Ni-hydrogen storage battery was manufactured.

In addition, in the above various sealed Ni-hydrogen storage batteries, the reason why the negative electrode capacity is made larger than the positive electrode capacity is 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 0.2 C (200 mA) at room temperature, 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 invention hydrogen storage alloys 1-18
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 significantly 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 13. 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 storage Ni--Zr alloy of the present invention is
In addition to being excellent in corrosion resistance to alkaline electrolytes, especially when used as a negative electrode active material of a sealed Ni-hydrogen battery, the negative electrode active material has all the properties required in a sufficiently satisfied state. The self-discharge of the storage battery is remarkably reduced, a large discharge capacity can be secured over a longer cycle life, and the content of expensive V component is relatively low, which contributes to cost reduction in the industry. It has useful properties.

Claims (4)

[Claims] 1. Zr: 10-37%, Ti: 5-25%, Mn: 4-20%, W: 0.01-13%, V: 0.1-15%, Fe: 0.01-5%, Al: 0.01 Hydrogen storage Ni-Zr-based alloy having a MgZn ₂ type crystal structure, characterized in that the hydrogen storage Ni-Zr-based alloy has a composition (up to wt%) of Ni and unavoidable impurities. 2. Zr: 10-37%, Ti: 5-25%, Mn: 4-20%, W: 0.01-13%, V: 0.1-15%, Fe: 0.01-5%, Al: 0.01 to 4.5%, containing, comprising using the remaining hydrogen absorbing Ni -Zr alloy having a MgZn ₂ type crystal structure having a composition (% by weight or more) of Ni and inevitable impurities as a negative electrode active material sealed Ni -Hydrogen storage battery. 3. Zr: 10 to 37%, Ti: 5 to 25%, Mn: 4 to 20%, W: 0.01 to 13%, V: 0.1 to 15%, Fe: 0.01 to 5%, Al: 0.01. to 4.5%, contains further, Cr: 0.05 to 6%, containing, rest with MgZn ₂ type crystal structure and having a composition consisting of Ni and inevitable impurities (% by weight or more) Hydrogen storage Ni-Zr alloy. 4. Zr: 10-37%, Ti: 5-25%, Mn: 4-20%, W: 0.01-13%, V: 0.1-15%, Fe: 0.01-5%, Al: 0.01 Hydrogen storage Ni-Zr having a MgZn ₂ -type crystal structure and containing Cr: 0.05 to 6%, and a balance of Ni and unavoidable impurities (above wt%). A sealed Ni-hydrogen storage battery using a base alloy as a negative electrode active material.