JPH0689711A - Sealed alkaline storabe battery - Google Patents

Abstract

PURPOSE:To provide a sealed alkaline storage battery whose internal resistance is free from risk of rising excessively and whose range of electrolyte having a high oxygen gas absorbing performance at the negative electrode is much larger than a conventional sealed alkaline storage battery. CONSTITUTION:A sealed alkaline storage battery includes a separator consisting of nonwoven cloth wherein the fibers at the surface confronting the negative electrode are thicker than the fibers situated inside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an aqueous solution of potassium hydroxide or sodium hydroxide as an electrolytic solution, nickel hydroxide, silver (I) oxide, silver (II) oxide, etc. as the main active material of the positive electrode, and uses cadmium. The present invention relates to a sealed alkaline storage battery used as a storage battery using a hydrogen storage alloy, zinc or the like as a main active material of a negative electrode.

[0002]

2. Description of the Related Art In a sealed alkaline storage battery, the amount of electrolyte is reduced and a non-woven fabric is used as a separator. Then, the capacity of the uncharged active material of the negative electrode is made larger than the capacity of the uncharged active material of the positive electrode, and at the end of charging of the battery, charging of the positive electrode ends before charging of the negative electrode, and oxygen gas is discharged from the positive electrode. Configure the battery to generate. By doing so, the oxygen gas generated from the positive electrode at the end of charging reaches the negative electrode through the pores between the fibers of the nonwoven fabric separator, is electrochemically reduced and consumed on the surface of the negative electrode, It is returned to the electrolyte. In this way, the accumulation of gas is prevented and the internal pressure in the sealed battery is prevented from rising significantly,
It prevents the electrolyte from decreasing. In such a battery, the alkaline electrolyte held between the fibers of the separator is responsible for ionic conduction between the positive and negative electrodes.

[0003]

As described above, in the conventional alkaline storage battery, when the amount of the electrolytic solution is reduced, the oxygen gas absorption performance of the negative electrode is improved and the internal pressure of the battery is lowered. When the battery is charged with a large current in a short time, the rate of generation of oxygen gas during overcharge increases, so in order to prevent the internal pressure of the battery from rising, the amount of electrolyte should be reduced as much as possible. It is necessary to improve the absorption performance.

On the other hand, when the amount of the electrolytic solution is reduced, the internal resistance of the battery increases and the polarization at the time of high rate discharge increases.

Therefore, the range of the electrolytic solution is selected so that the internal resistance does not significantly increase and the oxygen gas absorption performance in the negative electrode is high.

However, in the conventional sealed alkaline storage battery, when the charging current is large and the discharging current is large, the range of the amount of the electrolytic solution for suppressing the increase of the internal pressure and reducing the polarization during discharging is remarkably narrow. There was an inconvenience. In such a case, due to variations in the manufacturing process of the battery, there is a great risk that a battery having a high internal pressure rise or a battery having a large polarization at the time of high rate discharge is generated.

Therefore, there has been a demand for a sealed alkaline storage battery in which the internal resistance does not significantly increase and the range of the electrolyte having a high oxygen gas absorption performance in the negative electrode is wide.

[0008]

In order to solve the above problems, the present invention provides a sealed alkaline storage battery comprising a separator made of a non-woven fabric in which the fibers on the surface facing the negative electrode are thicker than the fibers inside.

[0009]

When the configuration of the present invention is adopted, the following action is obtained.

That is, in this sealed alkaline storage battery, since the fibers inside the separator are thinner than the fibers on the surface facing the negative electrode, the capillary force inside the separator is higher than the capillary force on the surface facing the negative electrode. As a result, the electrolytic solution of the separator of this battery tends to collect inside the separator rather than the surface facing the negative electrode, and even if the amount of the electrolytic solution of the separator is large, the amount of the electrolytic solution on the surface of the negative electrode is small, The oxygen gas absorption performance on the surface of the is improved. Moreover, since the amount of the electrolytic solution is not extremely reduced, the internal resistance is not increased.

Therefore, it is possible to obtain a sealed alkaline storage battery in which the internal resistance does not remarkably increase and the range of the electrolyte solution having a high oxygen gas absorption performance in the negative electrode is wide.

[0012]

EXAMPLES The present invention will be described in detail with reference to Examples. [Battery A] (Invention Product) This battery was manufactured as follows.

A basis weight (weight per unit area) of a polyamide fiber having a length of about 4 mm and a thickness of 2 denier 20
A non-woven fabric of g / m ^{2 and} a non-woven fabric having a basis weight of 40 g / m ^{2 made} of a polyamide fiber having an average denier of about 0.1 produced by the melt-blowing method are attached to each other to give a thickness of 0.15
A separator made of non-woven fabric having a weight per unit area of 60 g / m ² was manufactured.

Next, using the above separator, an alkaline storage battery was manufactured as follows.

That is, one known strip-shaped sintered nickel hydroxide electrode and one known cadmium sintered electrode are used as the positive electrode and the negative electrode, respectively, and one separator is interposed between these electrodes, The separator was wound while being pulled. In the separator, the surface having the 2-denier fiber was opposed to the negative electrode, and the surface having the thin fiber produced by the melt-blowing method was opposed to the positive electrode.

Then, this is housed in a cylindrical metal case, an alkaline electrolyte mainly composed of potassium hydroxide is injected, a battery lid with a safety valve is attached and sealed, and an AA type with a nominal capacity of 0.7 Ah. A sealed nickel-cadmium battery was manufactured.

The amount of electrolyte is 1.2 ml, 1.3 ml,
1.4 ml, 1.5 ml, 1.6 ml and 1.7 ml
I made one. [Battery B] (Comparative Example) In this battery, the same separator as in the battery A was made to face the positive electrode instead of facing the thick fiber surface to the negative electrode, and the thin fiber was made to face the negative electrode instead of facing the positive electrode. The other structure was the same as that of the battery A. [Battery C] (Comparative Example) In this battery, a non-woven fabric having a length of about 4 mm and a polyamide fiber of 2 denier having a thickness of 0.15 mm and a basis weight of 60 g / m ² was used instead of the separator of the battery A. Other configurations were the same as those of Battery A. [Battery D] (Comparative Example) In this battery, instead of the separator of the battery A, a thickness of 0.15 mm made of a polyamide fiber having an average denier of about 0.1 manufactured by a melt-blowing method and a basis weight of 60 g
A non-woven fabric of / m ² was used as the separator, and other configurations were the same as those of the battery A. <Experiment> The above four types of batteries were 0.7A at 25 ° C.
The battery was charged with a current of (1 hour rate), and the internal pressure of the battery was measured after 1.5 hours. The relationship between the internal pressure and the amount of electrolytic solution is shown in FIG.

The following can be seen from FIG.

That is, the batteries (B), (C) of the comparative example,
And (D), the amount of electrolyte is about 1.51 ml to about 1.
While the internal pressure exceeds 2 atm over 53 ml,
In the battery (A) of the present invention, the amount of electrolyte becomes a large value of 1.7 ml, and the internal pressure finally reaches 2 atm.
Therefore, it can be said that the battery of the present invention has a high oxygen gas absorption rate even when the amount of the electrolyte is large.

Further, these batteries were discharged with a current of 3.5 A (1/5 hour rate) until the terminal voltage became 0.8 V,
The terminal voltage at the 6th minute was measured. The relationship between the terminal voltage and the amount of electrolytic solution at the 6th minute is shown in FIG.

The following can be seen from FIG.

That is, each battery has an electrolytic solution amount of 1.4.
When it is less than ml, the discharge voltage is significantly reduced.

By combining FIG. 1 and FIG. 2, the following can be said. That is, in the battery (A) of the present invention, the range of the amount of the electrolytic solution in which the internal pressure at the time of rapid charging is lower than 2 atm and the voltage drop at the time of high rate discharging is not significant is 1.4 to 1.7 ml. In contrast to the wide range, the batteries (B), (C), and (D) of the comparative examples have an extremely narrow range from 1.4 ml to about 1.5 ml.

Therefore, in the sealed alkaline storage battery of the present invention, the internal resistance does not remarkably increase, and the range of the electrolyte having a high oxygen gas absorption performance in the negative electrode is higher than that of the conventional sealed alkaline storage battery. It can be said that it is extremely wide.

In the above embodiment, the nickel-cadmium battery was used as the alkaline storage battery. However, an aqueous solution of potassium hydroxide or sodium hydroxide was used as the electrolytic solution to obtain nickel hydroxide, silver (I) oxide, and oxide. Similar effects can be obtained also in the case of a storage battery in which secondary silver or the like is used as the main active material of the positive electrode and cadmium, zinc, hydrogen storage alloy or the like is used as the main active material of the negative electrode.

In the above embodiment, the case where the denier ratio of the thick fiber and the thin fiber is about 20 is used. However, if the denier ratio is about 4 or more, the same operation as the above embodiment is performed. The effect is obtained. In the above example, the case where the weight weight ratio of the thick fiber non-woven fabric and the thin fiber non-woven fabric is 0.5 has been described, but the weight weight ratio is in the range of 0.05 or more and 2.0 or less. If so, the same effects as those of the above-described embodiment can be obtained.

Further, in the above-mentioned embodiment, the case where the polyamide non-woven fabric is used for the separator has been described. In addition to this, for example, polyolefin or polystyrene is sulfonated, polyolefin is fluorinated, or the side chain of the polyolefin is used. Even when using a non-woven fabric made of hydrophilic and alkali-resistant fibers such as those having a hydrophilic group bonded, if the fiber-based structure is as described above, the same effect as in the above-mentioned examples can be obtained. To be

[0028]

EFFECTS OF THE INVENTION By using the constitution of the present invention, the range of the electrolyte having a high oxygen gas absorption performance in the negative electrode is remarkably higher than that of the conventional sealed alkaline storage battery without the internal resistance being remarkably increased. A wide sealed alkaline storage battery can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the internal pressure of a battery and the amount of electrolyte when it is charged for 1.5 hours at a current of 1 hour rate.

FIG. 2 is a graph showing the relationship between the terminal voltage and the amount of electrolytic solution at the 6th minute after discharging at a current of 1/5 hour rate.

[Explanation of symbols]

 (A) Battery of the present invention (B), (C), (D) Battery of Comparative Example

Claims (1)

[Claims] 1. A sealed alkaline storage battery comprising a separator made of a non-woven fabric in which the fibers on the surface facing the negative electrode are thicker than the fibers inside.