JPH07103435B2 - Hydrogen storage Ni-based alloy and sealed Ni-hydrogen storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a hydrogen storage Ni-based alloy having an MgZn ₂ type crystal structure, that is, a hexagonal C14 type crystal structure, and the hydrogen storage
The present invention relates to a sealed Ni-hydrogen storage battery using a Ni-based alloy as a negative electrode active material.

[Conventional technology]

In general, a sealed Ni-hydrogen storage battery, a negative electrode using a hydrogen storage alloy as an active material, a Ni positive electrode, and further composed of a separator and an alkaline electrolyte, and the hydrogen storage alloy constituting the negative electrode, a) Large hydrogen storage / release capacity near room temperature.

(B) The equilibrium hydrogen dissociation pressure corresponding to the plateau pressure 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 oxidizing ability (catalytic action) 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 a sealed Ni-hydrogen storage battery using a hydrogen storage alloy having such properties as the negative electrode active material 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 the negative electrode of a sealed Ni-hydrogen storage battery has been actively developed, for example, MgZn ₂ type crystal described in JP-A-61-45563. Many 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 the 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, from the above viewpoints, as a result of conducting 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, as a result of weight% (hereinafter % Indicates weight%), Ti: 5 to 20%, Zr: 10 to 37%, Mn: 4 to 18%, V: 0.1 to 15%, Cu: 0.1 to 7%, Al: 0.01 to 3.5%, Fe: 0.01 to 5%, and, if necessary, Cr: 0.05 to 6%, with the balance being Ni and inevitable impurities, a hydrogen storage Ni-based alloy is a MgZn ₂ type crystal. It has a structure (hexagonal C14 type crystal structure) and has the above-mentioned properties (a) to (g) required when it is used as a negative electrode active material of a sealed Ni-hydrogen storage battery in a sufficiently satisfied state. The sealed Ni-hydrogen storage battery used as the negative electrode active material has a large energy density and electric capacity, and has a long cycle life. In addition, we have obtained the knowledge that self-discharge is reduced, high-rate discharge and excellent discharge characteristics are also exhibited, and excellent performance is exhibited together with no pollution and low cost.

The present invention was made based on the above findings, and Ti: 5 to 20%, Zr: 10 to 37%, Mn: 4 to 18%, V: 0.1 to 15%, Cu: 0.1 to 7%, MgZn ₂ type crystal having a composition containing Al: 0.01 to 3.5%, Fe: 0.01 to 5%, and optionally Cr: 0.05 to 6%, and the balance of Ni and inevitable impurities. It is characterized by a hydrogen storage Ni-based alloy having a structure (hexagonal C14 type crystal structure) and a sealed Ni-hydrogen storage battery using this hydrogen storage Ni-based alloy as a negative electrode active material.

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

(A) Ti and Zr These components have the effect of providing the alloy with 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 content of Ti is less than 5% and Zr is less than 10%, the desired effect cannot be obtained, while if the content of Ti exceeds 20%, the equilibrium hydrogen dissociation pressure is, for example, 5 atm. As a result, the high hydrogen dissociation pressure is required to secure a large discharge capacity, which is unfavorable as a storage battery.
When the content of Zr exceeds 37%, there is no problem in terms of the hydrogen dissociation pressure dependence of the discharge capacity, but since the hydrogen storage / release capacity decreases, the content of Ti: 5 to 20
%, Zr: 10 to 37%.

(B) Mn 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 effect, but if the content is less than 4%, the desired effect cannot be obtained on the other hand, while the content is 18
If the content exceeds%, the hydrogen storage / release characteristics will be impaired, so the content was defined as 4-18%.

(C) V For the sealed Ni-hydrogen storage battery as described above, 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 V component content 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 leach into the electrolyte and promote self-discharge, so the content should be 0.1-15%. I decided.

(D) Cu The Cu component has the effect of further promoting the increase in the amount of hydrogen absorption / desorption and the optimization of the equilibrium hydrogen pressure in the coexistence with V, but if the content is less than 0.1%, it is desirable for the above action. However, if the content exceeds 7%, the hydrogen absorption / desorption amount is reduced, and the discharge capacity is reduced. Therefore, the content is defined as 0.1 to 7%. .

(E) Al Al component does not decrease hydrogen storage / release capacity,
It has the effect of further improving the corrosion resistance of the alloy and thus further suppressing the self-discharge of the storage battery, but if its content is less than 0.01%, the desired effect cannot be obtained on the other hand, while its content exceeds 3.5%. And the hydrogen storage / release capacity will be significantly reduced, so the content should be 0.01-3.5%.
I decided.

(F) Fe The Fe component has an effect of sizing the formed powder during powdering such as when it is used as a negative electrode active material of a storage battery, but if its content is less than 0.01%, it is desirable for the above effect. 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%.

(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%, the hydrogen storage / release capacity will decrease, so the content was defined as 0.05-6%.

〔Example〕

Next, the hydrogen storage Ni-based alloy of the present invention will be specifically described by way of examples.

Using a normal high frequency induction melting furnace, prepare Ni alloy melts having the composition shown in Table 1 in Ar atmosphere, cast into copper molds to make ingots, and then use this ingot.
Anneal in an Ar atmosphere at a predetermined temperature within a range of 900 to 1000 ° C. for 5 hours, then use a jaw crusher,
Coarse crushed to a diameter of 2 mm or less to coarse particles, and further finely crushed using a ball mill to a particle size of 350 mesh or less, and the present invention hydrogen storage Ni having MgZn ₂ type crystal structure.
Base alloys 1 to 18, comparative hydrogen storage Ni base alloys 1 to 12, and conventional hydrogen storage Ni base alloys were manufactured, respectively.

Then, various powdered hydrogen storage Ni-based alloys obtained as a result were used as an active material. First, a 2% aqueous solution of polyvinyl alcohol (PVA) was added to form a paste, and then a porosity of 95% was obtained. Filled with commercially available Ni whiskers non-woven fabric with, dried, and further pressed, plane dimensions: 42mm × 35m
Shape in m, thickness: 0.60 to 0.65 mm (active material filling amount: approx.
2.8 g), and a thin Ni plate to be the lead is attached to one side of this by welding to manufacture the negative electrode, while the positive electrode is made of Ni of the same size.
Prepare two sintered plates, place them on both sides of the negative electrode,
An open Ni-hydrogen storage battery was manufactured by charging a 30% KOH aqueous solution.

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 comparative hydrogen storage Ni-based alloys 1 to 12, the content of the constituent components (marked with * in Table 1) is out of the range of the present invention.

Next, for each of these various storage batteries, a charge / discharge test was carried out under the conditions of charge / discharge speed: 0.2 C, quantity of electricity charged: 130% of negative electrode capacity, and one charge / discharge cycle was defined as one cycle.
300 cycles after 100 cycles The discharge capacities after icicle and after 500 cycles were measured, and each of the above powdery hydrogen storage Ni-based alloys was used as the negative electrode. Both were positive electrode regulated AA size (capacity: 1000mAh) sealed Ni-hydrogen. Each of the storage batteries was assembled, and a self-discharge test was carried out for each, and the results are shown in Table 1.

Further, in detail, powdery hydrogen storage Ni shown in Table 1
Using alloy powder, plane size 90mm x 40mm, thickness: 0.60
~ 0.65mm, capacity: 1450 ~ 1500mAh (active material filling amount:
A negative electrode plate is 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 is approximately 6 g), while the positive electrode plate is a Ni whisker non-woven fabric with 95% porosity. Nickel [Ni (OH) ₂ ] was filled as an active material, dried, and further pressed, and then a lead was attached, and a flat dimension: 70 mm × 40 mm, thickness: 0.65 to 0.70 mm (capacity: 100
0 to 1050 mAh), and the negative electrode plate and positive electrode plate obtained as a result were housed in a case (which also serves as a terminal) together with the electrolytic solution in a spiral shape. A sealed Ni-hydrogen storage battery having a structure 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 addition, the self-discharge test starts with 0.2C (200mA) at room temperature for 7
Charged for an hour, then open the storage battery in a thermostatic chamber with the temperature set to 45 ° C (no load on the battery)
Then, the sample was allowed to stand for 1 week and 2 weeks, then taken out and discharged at room temperature for 0.2 C (200 mA) to determine the capacity remaining rate.

〔The invention's effect〕

From the results shown in Table 1, the present invention hydrogen storage Ni-based alloy 1
Each of the storage batteries using ~ 18 as the negative electrode active material has a high capacity, and the capacity decreases when the charge / discharge cycle is repeated as compared with the conventional storage battery using the hydrogen storage Ni-based alloy as the negative electrode active material. In contrast to the preferable result of being extremely small, the hydrogen-absorbing Ni-based alloys 1 to 12 of the comparative hydrogen-absorbing Ni-based alloys 1 to 12 are used as the negative-electrode active material.
It is clear that if the content of the constituent components of the Ni-based alloy deviates from the range of the present invention, the storage battery will not exhibit satisfactory performance in at least one of discharge capacity and self-discharge.

As described above, the hydrogen storage Ni-based alloy of the present invention, particularly when used as a negative electrode active material of a sealed Ni-hydrogen storage battery,
Since the negative electrode active material is sufficiently satisfied with the required characteristics, the self-discharge of the storage battery is significantly reduced, and a large discharge capacity can be secured over a long cycle life. Since the content of the V component is relatively low, it has industrially useful properties such as contributing to cost reduction.

Claims (4)

[Claims] 1. Ti: 5 to 20%, Zr: 10 to 37%, Mn: 4 to 18%, V: 0.1 to 15%, Cu: 0.1 to 7%, Al: 0.01 to 3.5%, Fe: 0.01 A hydrogen storage Ni-based alloy having a MgZn ₂ type crystal structure, characterized in that the content of MgZn ₂ is -5%, and the balance is Ni and unavoidable impurities (above weight%). 2. Ti: 5 to 20%, Zr: 10 to 37%, Mn: 4 to 18%, V: 0.1 to 15%, Cu: 0.1 to 7%, Al: 0.01 to 3.5%, Fe: 0.01 Hydrogen storage Ni with a MgZn ₂ type crystal structure containing ~ 5%, and the balance of Ni and unavoidable impurities (more than wt%)
A sealed Ni-hydrogen storage battery that uses a base alloy as a negative electrode active material. 3. Ti: 5 to 20%, Zr: 10 to 37%, Mn: 4 to 18%, V: 0.1 to 15%, Cu: 0.1 to 7%, Al: 0.01 to 3.5%, Fe: 0.01 5%, containing 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-based alloy. 4. Ti: 5 to 20%, Zr: 10 to 37%, Mn: 4 to 18%, V: 0.1 to 15%, Cu: 0.1 to 7%, Al: 0.01 to 3.5%, Fe: 0.01 Hydrogen storage Ni having a MgZn ₂ type crystal structure with a composition of (5% to 5%), Cr: 0.05 to 6%, and a balance of Ni and unavoidable impurities (more than wt%).
A sealed Ni-hydrogen storage battery that uses a base alloy as a negative electrode active material.