JPH0675398B2 - Sealed alkaline storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a sealed alkaline storage battery that uses a material that electrochemically occludes and releases hydrogen as a negative electrode active material, in other words, uses a hydrogen storage alloy as the negative electrode. The present invention relates to a sealed nickel-hydrogen storage battery.

[Prior Art] In general, a sealed nickel-hydrogen storage battery is composed of a negative electrode composed of a hydrogen storage alloy, a nickel positive electrode, a separator and an alkaline electrolyte, and the negative electrode constituting the structure includes (a) Has 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).

(C) It has corrosion resistance and durability (deterioration resistance) in an alkaline solution.

(D) Hydrogen oxidation 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-mentioned properties (a) to (g), and a sealed nickel-hydrogen storage battery using a hydrogen storage alloy having such properties as a negative electrode has a large discharge capacity and a long charge / discharge cycle. Longevity, excellent rapid charge / discharge characteristics,
It is well known that it exhibits favorable performances such as low self-discharge, and a sealed nickel-hydrogen storage battery using a large number of hydrogen storage alloys as a negative electrode along these lines has been proposed. No. 61-45563.

Ti: 15 to 20%, V: 15 to 40%, Zr: 10 to 20%, and the balance 30 to 55% of Ni and inevitable impurities (above atomic%, below% atomic% The hydrogen storage alloy having (shown below) (hereinafter referred to as a conventional hydrogen storage alloy) has the following properties (a) to (g) required for a storage battery negative electrode:
Since it has properties excluding (c) and (g), it is used as a negative electrode for a storage battery, and thus the storage battery has a large energy density and electric capacity and a long cycle life, and is useful in combination with pollution-free. It has characteristics.

[Problems to be Solved by the Invention]

However, the above conventional hydrogen storage alloy, among the above properties,
In particular, since the property of (c) is not sufficient, when this is used as the negative electrode, the storage battery has a large self-discharge, and further, the manufacturing cost of the storage battery for containing a large amount of extremely expensive V increases accordingly. It has problems.

[Means for Solving the Problems]

Therefore, the present inventors, from the above viewpoint, pay attention to the above conventional hydrogen storage alloy used as the negative electrode of the sealed nickel-hydrogen storage battery, without impairing the excellent characteristics that it has, That is, as a result of carrying out research to develop a sealed nickel-hydrogen storage battery that has these characteristics and further has small self-discharge and low cost, Ti: 13 to 18%, Zr: 15 to 20%, Mn: 10 to 15%, V: 5 to 12%, Cu: 3 to 6%, and the remaining 33 to 45% of Ni and unavoidable impurities are hydrogen storage alloys that are sealed nickel- In addition to having all of the above-mentioned properties required for the negative electrode of the hydrogen storage battery, when it is used as the negative electrode of the storage battery, the storage battery has a large energy density and electric capacity and exhibits a long cycle life. , Self-discharge becomes smaller, Furthermore, we have obtained the knowledge that it has excellent high-rate charge / discharge characteristics, and that it will exhibit excellent performance in combination with pollution-free and low cost.

The present invention has been made based on the above findings, and the reason why the component composition of the hydrogen storage alloy is limited as described above will be described below.

(A) Ti and Zr These components have the effect of providing the alloy with desirable hydrogen absorption / desorption characteristics in the coexisting state.
When the atomic ratio of hydrogen is 45/55, it exhibits excellent hydrogen absorption / desorption characteristics, and it has a relatively low equilibrium hydrogen dissociation pressure (plateau pressure) at room temperature, for example, 5 atm or less, which is preferable for negative electrodes. However, if the Ti content is less than 13% and the Zr content is less than 15%, the desired hydrogen absorption / desorption characteristics cannot be secured.
It is necessary to contain Ti: 13% or more and Zr: 15% or more, and in this case, if the atomic ratio of Ti / Zr is 55/45 or more, the dissociation pressure increases to 5 atm or more, and a large discharge capacity In order to secure a high hydrogen pressure, it becomes unfavorable for a storage battery, and when it is 40/60 or less, there is no problem in the dependence of the discharge capacity on the hydrogen pressure, but the hydrogen storage / release capacity is low. Since it will decrease, Ti
It is desirable to maintain the atomic ratio of / Zr between 40/60 and 55/45, so that the Ti and Zr contents are respectively Ti: 18
%, Zr: 20% must not be exceeded.

(B) Mn The Mn component increases hydrogen storage / release capacity, and improves the corrosion resistance and durability of the alloy in an alkaline electrolyte,
Especially when used as a negative electrode of a sealed type storage battery, it has an effect of suppressing self-discharge, but if its content is less than 10%, the desired effect cannot be obtained, while its content is 15%.
If the content exceeds the range, the hydrogen absorption / desorption characteristics will be impaired, so the content was defined as 10 to 15%.

(C) V and Cu As described above, in the nickel-hydrogen storage battery, it is desired that the equilibrium 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. And Cu components have the effect of contributing to such an increase in hydrogen storage / release amount and optimization of the equilibrium hydrogen pressure, but if their contents are V: less than 5% and Cu: less than 3%, the above-mentioned action occurs. On the other hand, when the content of V exceeds 12%, the equilibrium hydrogen pressure becomes too high, and V dissolves into the electrolytic solution.
Self-discharge is promoted, and with Cu, 6
If the content exceeds V, the hydrogen absorption / desorption amount will decrease, and the discharge capacity will decrease.
2%, Cu: 3-6%.

(D) Ni As the Ni component, oxygen generated in the positive electrode at the time of overcharging reacts with hydrogen on the surface of the negative electrode to become water as the performance of the storage battery.
It has a catalytic action for hydrogen oxidation and is an essential component as a negative electrode constituent component of a sealed nickel-hydrogen storage battery, but if its content is less than 33%, the above action is not sufficiently exhibited, and further the hydrogen storage / release capacity is also high. On the other hand, if the content exceeds 45%, the equilibrium hydrogen pressure will rise, resulting in a decrease in the discharge capacity of the storage battery.
It was set at 33 to 45%.

In the sealed nickel-hydrogen storage battery of the present invention, in order to manufacture a negative electrode using the above hydrogen storage alloy, generally, a Ni alloy molten metal having a predetermined composition is first prepared by a usual melting method, and this is cast. After casting into a lump, coarse pulverization and fine pulverization are added to make powder, and a binder etc. is added to this powder,
A well-known method is used in which after kneading well to make a paste, the nickel whisker nonwoven fabric is uniformly filled and dried.

〔Example〕

Next, the sealed nickel-hydrogen storage battery of the present invention will be specifically described by way of Examples.

Using an argon arc melting furnace, a water-cooled copper crucible was used to prepare molten Ni alloys each having the composition shown in Table 1, and after casting into ingots, the ingots were heated in an argon gas atmosphere at a temperature of 1050. Annealed at 10 ° C. for 10 hours, then coarsely crushed using a stamp mill and jaw crusher to a diameter of 2 mm or less, then finely pulverized with an attritor to a particle size of 350 mesh or less, Then, using the various hydrogen storage alloy powder obtained as a result,
First, after adding a 2% aqueous solution of polyvinyl alcohol (PVA) to form a paste, it is filled into a commercially available nickel whisker non-woven fabric having a porosity of 95% and dried.
Further pressurize it to a plane size of 42 mm x 35 mm and thickness: 0.
The shape of 60-0.65mm (filling amount of active material: about 2.8g) is used to manufacture a negative electrode plate by welding a thin nickel plate to be a lead on one side, while a positive electrode plate of the same size sintered nickel Two positive electrodes were prepared, placed on both sides of the negative electrode plate, charged with a 30% KOH aqueous solution, and the storage battery 1 of the present invention was prepared.
.About.9, comparative storage batteries 1 to 9, and conventional storage batteries, respectively.

Regarding the various storage batteries obtained as a result, all of them were used as open batteries and the capacity of the positive electrode was made significantly larger than that of the negative electrode in order to make it possible to measure the capacity of the negative electrode (negative electrode regulation). Rule).

Further, in the above-mentioned comparative storage batteries 1 to 9, in the hydrogen storage alloy used for the negative electrode, the content of any one of the constituent components thereof (marked with * in Table 1) is within the range of the present invention. Further, in the conventional storage battery, an alloy having a composition corresponding to the above conventional hydrogen storage alloy is used for the negative electrode that constitutes the conventional storage battery.

Next, for these storage batteries, charge / discharge rate: 0.2C,
Charging electricity quantity: A charge / discharge test was conducted under the condition of 130% of the negative electrode capacity, and one charge and discharge were regarded as one cycle, and the discharge capacity after 100 cycles, 300 cycles, and 500 cycles was measured, respectively. The results are shown in Table 1.

Furthermore, from the various hydrogen-absorbing alloy powders shown in Table 1, those shown in Table 2 were selected and used as the negative electrode, and the present invention sealed nickel of AA size (capacity: 1000 mAh) regulated by the positive electrode. -Hydrogen storage batteries a to d (hereinafter referred to as the present invention storage batteries a to d), comparative sealed nickel-hydrogen batteries a and b (hereinafter referred to as comparative storage batteries a and b), and conventional sealed nickel-hydrogen storage batteries (hereinafter referred to as (As for conventional storage battery), each is assembled, self-discharge test is performed for this,
The results are shown in Table 2.

More specifically, the hydrogen storage alloy powder having the composition shown in Table 2 is used, the plane size is 90 mm × 40 mm, the thickness: 0.60 to
0.65mm, capacity: 1450 ~ 1500mAh (active material Filling amount: about 6 g) except that the negative electrode plate is manufactured under the same conditions as the negative electrode plate of the storage battery used in the above charge and discharge test, while the positive electrode plate is a nickel whisker non-woven cloth having a porosity of 95%. Filled with nickel hydroxide {Ni (OH) ₂ } as the active material, dried, and further pressed, and then attached with leads, with plane dimensions: 70 mm × 40 mm, thickness: 0.65 to 0.70 mm (capacity: capacity : 1000 to 1050mAh) and obtained as a result A sealed nickel-hydrogen storage battery having a structure in which it is housed in a case (which is also used as a terminal) together with an electrolytic solution in a spiral shape via a separator, that is, the storage batteries a to d of the present invention and comparative storage batteries a and b. , And a conventional storage battery were manufactured respectively.

In addition, in the above various sealed nickel-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, all of the storage batteries 1 to 9 of the present invention have a high capacity and show a preferable result that the capacity decrease is small when the charge and discharge cycles are repeated, whereas the negative electrodes Comparative storage batteries 1 to 5, 8 and 9 whose composition of the hydrogen storage alloy constituting
Is a comparatively low discharge capacity, and a large degree of capacity decrease due to repeated charge and discharge cycles, while the composition of the hydrogen storage alloy that also constitutes the negative electrode is outside the scope of the present invention. In the case of, the discharge capacity is almost at the same level, but there is a problem in terms of self-discharge described later, and even if the content of any one of the constituent components of the hydrogen storage alloy constituting the negative electrode is If the value deviates from the range, one of the properties required for the above-mentioned storage battery negative electrode will be deteriorated, and therefore, performance sufficiently satisfactory in at least one of the discharge capacity and self-discharge of the storage battery will be exhibited. Obviously not.

That is, as shown in Table 2, the comparative storage batteries a and b exhibiting a high capacity and the conventional storage battery also have poor self-discharge characteristics,
On the other hand, each of the storage batteries a to d of the present invention has a significantly low self-discharge and a high remaining capacity.

As described above, in the sealed nickel-hydrogen storage battery of the present invention, the hydrogen storage alloy that constitutes the negative electrode of this battery has excellent corrosion resistance and durability as compared with the conventional hydrogen storage alloy, and thus self-discharge. Is significantly reduced, a large discharge capacity can be secured over a longer cycle life, and the content of expensive V component is relatively low, resulting in low cost and required for the negative electrode of the storage battery. Since it has all the properties, it exhibits excellent performance over a remarkably long period of time.

Claims (1)

[Claims] 1. The negative electrode contains Ti: 13 to 18%, Zr: 15 to 20%, Mn: 10 to 15%, V: 5 to 12%, Cu: 3 to 6% in atomic%. A sealed alkaline storage battery, characterized in that the remainder is composed of a hydrogen storage alloy having a composition of 33 to 45% Ni and inevitable impurities.