JPH02263944A - Hydrogen storage ni-zr series alloy and closed-type ni-hydrogen storage battery - Google Patents

Abstract

PURPOSE:To obtain the hydrogen storage Ni-Zr series alloy having high hydrogen occluding and discharging capacity and low dissociation pressure of equilibrium hydrogen in the region of room temp. and having excellent alkali resistance at a low cost by specifying the compsn. constituted of Ti, Zr, Mn, W, Fe and Ni. CONSTITUTION:The hydrogen storage Ni-Zr series alloy has the compsn. contg., by weight, 5 to 20% Ti, 10 to 37% Zr, 5 to 30% Mn, 0.01 to 15% W and 1 to 30% Fe, furthermore contg., at need, one or both of 0.05 to 6% Cr and 0.01 to 5% Al and the balance Ni with inevitable impurities and has an MgZn2-type crystal structure, which shows excellent corrosion resistance and durability in an alkaline electrolytic soln., has high hydrogen occluding and discharging capacity and low dissociation pressure of equilibrium hydrogen in the region of room temp., has high hydrogen oxidizing capacity, is hard to pulverize, causes no pollution and is low-cost. Thus, by using the alloy as the active material in the negative electrode, the closed type Ni hydrogen storage battery having high discharging capacity and showing preferable capacity such as prolonged charging discharging cycle life, excellent rapid charging- discharging properties and low self-discharging can be obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is based on MgZn2 type crystal structure, that is, hexagonal C
The present invention relates to a hydrogen-absorbing NlZr alloy having a type 14 crystal structure and a sealed Nl-hydrogen storage battery using this hydrogen-absorbing Ni-Zr alloy as a negative electrode active material.

[Conventional technology]

Generally, a sealed Nl-hydrogen storage battery is composed of a negative electrode using a hydrogen storage alloy as an active material, an Nl positive electrode, a separator, and an alkaline electrolyte, and the hydrogen storage alloy constituting the negative electrode includes: a) High hydrogen absorption and release ability 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 electrolytes.

(d) High hydrogen oxidation ability (catalytic action).

<e> Pulverization due to repeated absorption and release of hydrogen is unlikely to occur.

(r) No (low) pollution.

(g) It is low cost.

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

Therefore, the development of hydrogen storage alloys particularly suitable for use as active materials constituting the negative electrode of sealed Ni-hydrogen storage batteries has been actively carried out. A large number of hydrogen storage alloys have been proposed, including hydrogen storage alloys having a Z-type crystal structure, that is, a hexagonal C14-type crystal structure.

[Problem to be solved by the invention]

However, none of the hydrogen storage alloys that have already been proposed satisfies all of the above properties required for use as negative electrode active materials in sealed Nl-hydrogen storage batteries, and further development is desired. The current situation is that

[Means to solve the problem]

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to develop a hydrogen storage alloy particularly suitable for use as a negative electrode active material of a sealed Ni-hydrogen storage battery. % indicates weight%), TI = 5-20%, Zr: 10-37%, Mn
: 5-30%, W: 0.01-15%, Fe: 1
~30%, and further optionally Cr1.05~6% and Al2: 0.01~59
A hydrogen-absorbing Ni-Zr alloy containing one or two of fi, with the remainder consisting of Nl and unavoidable impurities, is M g Z n 2
type crystal structure (hexagonal C14 type crystal structure), and fully satisfies the above properties (a) to (g) required when used as a negative electrode active material of a sealed Ni-hydrogen storage battery, Therefore, a sealed Ni-hydrogen storage battery using this as a negative electrode active material has high energy density and electric capacity, has a long cycle life, has low self-discharge, and has a high rate of light and discharge. They found that it has excellent characteristics, is non-polluting, and is low cost, and will exhibit excellent performance.

This invention was made based on the above findings, and includes: T1: 5-20%, Zr: 10-37%,
Mn: 5-30%, W: o, ot-15%,
Contains Fe: 1 to 30%, and if necessary, Cr: 0.05 to 6% and J: o, ot to 5%, or 2f! I.

MgZn2 type crystal structure (hexagonal C14 type crystal structure) with a composition containing Nl and unavoidable impurities.
The present invention is characterized by a hydrogen-absorbing Ni-Zr-based alloy having the following characteristics, and a sealed Ni-hydrogen storage battery using this hydrogen-absorbing Ni-Zr-based alloy as a negative electrode active material.

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

(a) TI and Zr These components, when coexisting, provide the alloy with desirable hydrogen storage and release properties, and have the effect of lowering the equilibrium hydrogen dissociation pressure (plateau pressure) at room temperature to, for example, 5 atmospheres or less. However, if the T content is less than 175% and the Zr content is less than 10%, the desired effect cannot be obtained, whereas if the TI content exceeds 20%, the equilibrium hydrogen dissociation pressure may exceed, for example, 5 atm. began to rise,
In order to ensure a large discharge capacity, a high hydrogen dissociation pressure is required, making it undesirable as a storage battery, and if the Zr content exceeds 37%, the dependence of the discharge capacity on the hydrogen dissociation pressure will deteriorate. Although there is no problem, the hydrogen storage and desorption ability decreases, so the contents were determined to be TI+5 to 20% and Zr: 10 to 37%, respectively.

(b) Mn The Mn component not only improves hydrogen storage and desorption ability, but also improves the corrosion resistance and durability of the alloy in alkaline electrolytes, and also has the ability to prevent self-discharge when used as a negative electrode active material for #i batteries. It has a suppressing effect, but if its content is less than 5%, the desired effect cannot be obtained in the said effect, while if its content exceeds 30%, hydrogen storage and release properties will be impaired. , its content was determined to be 5 to 30%.

(e) W The W component has the effect of further improving the corrosion resistance of the alloy in an alkaline electrolyte, improving durability, and suppressing self-discharge when used as a negative electrode active material for storage batteries. If the content is less than 0.015, the desired effect cannot be obtained; on the other hand, if the content is less than 15%
If the content exceeds 0.01% to 15%, the hydrogen storage/release properties will be impaired.

(d) Fe The Fc component has the effect of further stabilizing the hydride and thereby stabilizing the storage battery performance, and even if it is used as a partial substitute for Ni, the effects brought about by Ni will be impaired. However, if the content is less than 1%, the desired effect will not be obtained, while if the content exceeds 3096, the hydrogen storage capacity will decrease. Therefore, the content was determined to be 1 to 30%.

(e) Cr and AI These components have the effect of further improving corrosion resistance in an alkaline electrolyte without reducing the hydrogen storage and desorption ability, so they are included as necessary. Cr: less than 0.05% and l!, respectively. :0.0
If the content is less than 1%, the desired effect of improving corrosion resistance cannot be obtained, and on the other hand, the -am content is Cr: 6% and Af): 5%, respectively.
If the content exceeds Cr: 0.05 to 6%, the hydrogen storage and desorption ability will decrease, respectively.
The resistance was determined to be 20Ω and 1 to 5%.

〔Example〕

Next, the hydrogen-absorbing Ni--Zr alloy of the present invention will be specifically explained with reference to Examples.

Using an ordinary high-frequency induction melting furnace, prepare molten Ni alloys having the compositions shown in Table 1 in an atmosphere of A, and cast them into copper molds to form ingots. Annealed in an atmosphere at a predetermined temperature within the range of 900 to 1000°C for 5 hours, then coarsely crushed using a show crusher to obtain coarse particles with a diameter of 2 mm or less, and then finely crushed using a ball mill. te350n+es
By setting the particle size to h or less, M g Z n
Hydrogen storage alloys 1 to 20 of the present invention having type 2 crystal structure,
Comparative hydrogen storage alloys 1 to 9 and conventional hydrogen storage alloys were each manufactured.

Next, various powdered hydrogen storage alloys obtained as a result are used as active materials, and a 2% aqueous solution of polyvinyl alcohol (PVA) is added thereto to form a paste, which has a porosity of 95%. Commercially available Nl whisker non-woven 6
1, dried, and further pressurized, planar dimension: 4
2mm x 35mm, thickness: 0.60~0.
The shape is 85 m + s (active material filling amount: about 2.8 g),
N is the lead on the - side of this! A negative electrode is manufactured by attaching a thin plate by welding, while two Ni sintered plates of the same size are prepared as positive electrodes and placed on both sides of the negative electrode.
A sealed Nl-hydrogen storage battery was manufactured by charging an OH aqueous solution.

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

Furthermore, the component contents (those marked with * in Table 1) of the Comparative Hydrogen Storage Alloys 1 to 9 are outside the scope of the present invention.

Next, for these various storage batteries, the charging and discharging speed:
A charging/discharging test was conducted under the conditions of 0.2C, charging electricity amount: 130% of the negative electrode capacity, one charge and discharge was one cycle, and after 100 cycles, 200 cycles, and 30
The discharge capacity after 0 cycles was measured, and each of the above-mentioned powdered hydrogen storage alloys was used as a negative electrode.
A sealed type Nl-hydrogen storage battery was assembled and subjected to a self-discharge test, and the results are shown in Table 1.

Furthermore, in detail, using the powdered hydrogen storage alloy powder shown in Table 1, the planar size was 90 mw x 4 (1 mm
Thickness: 0.80-0.65mm, volume u:
The 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 charge was 1450 to 1500 mAh (active material filling amount: approximately 6 g), while the positive electrode plate was manufactured at 95%
A Nl whisker nonwoven fabric with a porosity of 2 is filled with nickel hydroxide (Nl(OH)2) as an active material, dried, and further pressed, and then a lead is attached to the fabric. Planar dimensions: 70nos x 40mm, thickness: 0.65~
0.70mm shape (capacity: 1000-1050rA
The negative tit and positive electrode plate obtained as a result are formed into a spiral shape with a separator interposed between them, and are placed in a case together with an electrolyte (this also serves as the ○ terminal).
A sealed type Ni-hydrogen storage battery was manufactured.

In addition, in the various sealed Ni-hydrogen storage batteries described above, the reason why the negative electrode capacity is made larger than the positive electrode capacity is to configure a storage battery with a positive electrode rule.

In addition, the self-discharge test was first conducted at room temperature [1,2C (200C)
mA) for 7 hours, then the storage battery was set at a temperature of 45°C and left in an open circuit state (no load applied to the battery) in a thermostatic oven for one week and then for two weeks. The battery was discharged at 0.2 C (200 mA) at room temperature, and the remaining capacity was determined.

Furthermore, regarding the various hydrogen storage alloys mentioned above, generally H
Using a method called the Uey test, a test piece was cut from the above ingot, embedded in plastic resin, the corroded surface was polished with Emery Vapor #600, and then placed in an Erlenmeyer flask with a cold finger condenser. , 144 in a boiling 30% aqueous KOH solution.
An alkaline electrolyte corrosion test was carried out under the condition of holding time, and the corrosion loss after the test was measured. The results of these measurements are also shown in Table 1.

〔Effect of the invention〕

From the results shown in Table 1, hydrogen storage alloys 1 to 2 of the present invention
0 exhibits superior corrosion resistance to alkaline electrolytes compared to conventional hydrogen storage alloys, and furthermore, storage batteries using these as negative electrode active materials have high capacity and are superior to conventional hydrogen storage alloys. Compared to storage batteries using alloys, charging and
On the other hand, as seen in Comparative Hydrogen Storage Alloys 1 to 9, even if the content of any of the constituent components is within the scope of the present invention, It is clear that if the material is removed from the surface, the corrosion resistance against alkaline electrolytes will decrease, and if it is used as a negative electrode active material in a storage battery, there will be a tendency for the storage battery's discharge capacity and self-discharge to deteriorate.

As mentioned above, the hydrogen-absorbing Ni-Zr alloy of the present invention has excellent corrosion resistance against alkaline electrolytes, and
In particular, when used as a negative electrode active material in a sealed Nl-Hydrogen storage battery, it fully satisfies all the characteristics required for a negative electrode active material, significantly reducing self-discharge of the storage battery and resulting in a longer cycle time. It has industrially useful characteristics, such as ensuring a large discharge capacity throughout its life.

Claims (4)

[Claims] (1) Ti: 5-20%, Zr: 10-37%, Mn:
5-30%, W: 0.01-15%, Fe: 1-30%
A hydrogen-absorbing Ni-Zr alloy having a MgZn_2 type crystal structure, characterized in that it has a composition (by weight %) of the following, with the remainder consisting of Ni and unavoidable impurities. (2) Ti: 5-20%, Zr: 10-37%, Mn:
5-30%, W: 0.01-15%, Fe: 1-30%
A sealed Ni-hydrogen storage battery using, as a negative electrode active material, a hydrogen-absorbing Ni-Zr alloy having a MgZn_2 type crystal structure having a composition (by weight %) of Ni and unavoidable impurities. (3) Ti: 5-20%, Zr: 10-37%, Mn:
5-30%, W: 0.01-15%, Fe: 1-30%
, and further contains one or two of Cr: 0.05-6% and Al: 0.01-5%, with the remainder consisting of Ni and unavoidable impurities (more than %) having a MgZn_2 type crystal structure. (4) Ti: 5-20%, Zr: 10-37%, Mn:
5-30%, W: 0.01-15%, Fe: 1-30%
, and further contains one or two of Cr: 0.05-6% and Al: 0.01-5%, with the remainder consisting of Ni and unavoidable impurities (more than A sealed Ni-hydrogen storage battery using a hydrogen-absorbing Ni-Zr alloy having a MgZn_2-type crystal structure with %) as a negative electrode active material.