JPS61151965A - alkaline storage battery - Google Patents

Abstract

PURPOSE:To improve the gas permeability and the liquid retention rate of a separator, so as to reduce the internal pressure during high rate charging of the battery stated in the headline by making the separator to have a through hole inside its fiber as well as fine pores provided at the fiber surface, and penetrating into the fiber inside. CONSTITUTION:A separator is composed of unwoven fabric made of irregularly arranged fibers, and the fiber 1 is a hollow fiber providing an inside hole 2 presenting 20-30% volumetric ratio as well as providing on its surface fine pores 3 penetrating into the fiber inside. The liquid retention rate of the separator is increased because of an electrolytic solution is retained in the inside hole. And, since a part of the electrolytic solution being retained on the fiber surface can also be retained in the fiber inside, the quantity of the electrolytic solution existing among the fibers is reduced relatively, and the gas permeability is made to increase. By the result, it is possible to generate the oxygen absorbing reaction at the negative electrode more speedily by the improvement of the liquid retention rate and the gas permeability of the separator.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a separator for an alkaline storage battery having a spiral electrode body.

Conventional technology In general, separators for alkaline batteries are placed in an alkaline electrolyte and are interposed between positive and negative electrodes to prevent contact between the two, as well as to sufficiently hold the electrolyte and allow the electromotive reaction to proceed smoothly. Must. Therefore, separators for alkaline batteries are required to have high alkali resistance and high electrolyte retention capacity. In particular, in sealed alkaline storage batteries, in order to ensure rapid charging performance, the amount of electrolyte is set to the minimum required amount, and a separator with good ion conductivity can be obtained with a small amount of electrolyte and has good liquid retention. is necessary.

Conventionally, as this type of separator, a nonwoven fabric mainly made of nylon or polypropylene fibers has been generally used.

Among these, nylon fiber nonwoven fabric separators, which have sufficient liquid retention due to the hydrophilic nature of the fibers themselves and have excellent gas permeability when containing an electrolyte, are used for this type of sealed alkaline storage batteries, such as nickel and Commonly used in cadmium storage batteries. In recent years, improvements have been made to the positive electrode, negative electrode, and electrolyte to enable more rapid charging, and various improvements to the separator have also been reported.

Improvements to nylon separators include: ■ Polymerization of caprolactam in the presence of oxidation products of polyethylene glycol ■ Post-treatment with ethylene oxide, potassium hydroxide, and maleic acid copolymers ■ Squash There are processing methods, etc., and there is also a hollow system in which holes are created inside the fiber, apparently to lower the specific gravity. As for products with improved high moisture absorption, their alkali resistance is slightly inferior to conventional products, and hollow fibers currently have no improvement in liquid retention because there are no through holes between the hollow part and the outside. Ta.

On the other hand, in order to overcome the problem of alkali resistance of nylon fibers at high temperatures, some nonwoven fabrics mainly made of polyprolene fibers, which have greater chemical stability than -nylon in a wider temperature range, have been put into practical use. However, since polypropylene am itself is chemically stable, there is a problem in that its hydrophilicity and liquid retention properties are significantly deteriorated compared to nylon.

Improvements in this problem include (1) significant improvement in porosity and pore volume in the nonwoven fabric state; ■Add surfactant to improve hydrophilicity. ■Conventions such as blending with nylon fibers and making use of the advantages of each in a mixed paper state are being carried out.0 Although these methods apparently improve liquid retention in the initial stage, they do not provide permanent maintenance. The current situation was that the liquid properties were not improved.

Problems to be Solved by the Invention In a sealed alkaline storage battery that has a group of electrode plates in which a nonwoven fabric of nylon or polypropylene fibers is used as a separator and is interposed between the positive and negative electrode plates, the conventional charging rate is up to 1G. Today, although it is desired to charge at a higher rate with a constant discharge capacity or to improve the discharge capacity with a constant charging rate, it is not possible to keep the internal pressure of the battery low during charging, so it is difficult to maintain the above characteristics. In order to solve this problem, the present invention has a method of interposing a band-shaped separator between the positive and negative electrode plates and winding them in a spiral shape. In a sealed alkaline storage battery having a group of electrode plates, the separator is made of a non-woven fabric in which fibers are arranged irregularly, and the fibers are hollow fibers with 2Q to 30 holes inside, and the surface has internal and external holes. It is characterized in that it has microscopic holes that penetrate through it. In the case of nylon fiber, the apparent specific gravity is 0.60 to 0.70. In the case of polypropylene fibers, the apparent specific gravity is 0.40 to 0.6o.

In a sealed alkaline storage battery in which an electrolyte is contained in a group of spirally wound electrode plates with a band-shaped separator interposed between the positive and negative electrode plates, the electrolyte content distribution is based on the hydrophilicity of the positive electrode, negative electrode, and separator. It is determined by the properties and porosity, and when the amount of electrolyte exceeds the saturation amount of these liquids, it exists in a free state.

In order to improve the oxygen absorption reactivity at the negative electrode during charging, (1) Improve the gas permeability of the separator.

By increasing the liquid retention capacity of the reseparator and reducing the amount of electrolyte in the positive and negative electrode plates, especially the amount of electrolyte in the negative electrode, the total oxygen absorption reaction interface of the negative electrode is increased.

When using a nonwoven fabric made of fibers having pores inside the fibers and having fine pores penetrating the inside of the fibers on its surface by means of the above-mentioned method of the present invention, compared to conventional nylon fibers, Whereas the electrolyte was held only by the hydrophilic groups on the surface, the electrolyte is also held in the pores within the fibers, increasing the liquid retention rate of the separator. Furthermore, since a portion of the electrolytic solution held on the fiber surface is retained inside the fiber, the amount of electrolytic solution existing between the fibers is relatively reduced, thereby improving gas permeability. As a result, the liquid retention rate and gas permeability of the separator are improved, so that the oxygen absorption reaction at the negative electrode occurs more quickly.

Example The present invention will be explained in detail below.

The first figure shows an enlarged view of the fiber, in which 1 is the fiber, 2 is the hole provided inside the fiber, and 3 is the micropore provided on the surface.

Now, in a nonwoven fabric with a thickness of 0.22 mm using nylon fibers with a fiber diameter of 2 to 3 deniers, a smooth surface without micropores, and a fiber length of about 6 to 10 m + n, the porosity inside the fibers and the specific gravity are 1.30. The relationship between potassium hydroxide retention rate and potassium hydroxide retention rate is the second
As shown in Figure A, the liquid retention rate increased when the porosity was 16 cm or more, but the effect was small.

Further, even when a concave portion was formed on the outer surface of the fiber by post-treatment and the apparent specific gravity of the fiber was changed from 0.70 to 1.14, the liquid retention rate did not change at all.

Next, in a nonwoven fabric using the fibers shown in Figure 1, in which a large number of micropores with a porosity of about 25 mm were provided on the fiber surface, and all of the pores penetrated through the fibers, the pores in the fibers were The relationship between the liquid retention rate and the porosity is 20 to 30, as shown in Figure 2.
It has been confirmed in experiments that the liquid retention rate increases significantly in the above cases. Moreover, the apparent specific gravity in this range is 0.
It was confirmed by measurement that it was 60 to 0.70. In addition, polypropylene fibers have similar effects,
The apparent specific gravity was 0.40 to 0.60.

A sintered nickel positive electrode plate and a paste-type cadmium negative electrode plate are interposed with a nylon fiber non-woven fabric ladle, and the spirally wound electrode plates contain an electrolyte mainly composed of potassium hydroxide. In a sealed nickel-cadmium storage battery, the amount of electrolyte is 62.8 Co, the amount of electrolyte is constant at 4 mm, and the above-mentioned clarifier is used with a fiber diameter of 2 to 3 deniers and a fiber length of about 5 to 1 mm. When using fiber (a)
The fiber diameter is 2 to 3 denier (the denier here refers to the general fiber diameter), the fiber length is about 6 to 10111!11, and the fiber has 20 to 30% pores inside. A fiber with an apparent specific gravity of 0.60 to 0.70 that has fine pores on its surface that penetrate into the internal pores: When used ←)
As a result of measuring the internal pressure during 2G charging at an ambient temperature of 0°C, good results were obtained as shown in Figure 3.
I was attacked. Also, charging is 4G at 2G at an ambient temperature of 0°C.
As a result of carrying out a cycle life test with a discharge current of 1 G for 6 minutes, good results were obtained as shown in FIG.

Furthermore, using a conventional separator, the amount of electrolyte was reduced to 2.80
0/IIAkL (c) and when the electrolyte amount is 3.2 cc/mAh using the separator of the present invention)
As a result of measuring the internal pressure during 1G charging at an ambient temperature of 0°C, the internal pressure was approximately 3 kg/af for both batteries at 200% charging electricity, which was the same (9). Further, as shown in FIG. 6, the capacity at 1G discharge at this time was better when the separator of the present invention was used and the amount of electrolyte was increased.

As a result, it was found that when the separator according to the present invention was used, the discharging performance was improved without impairing the charging performance even when the amount of electrolyte was increased.

The results were as follows.

Effects of the Invention As described above, according to the present invention, 20 to 30% of
By having micropores that penetrate inside the fiber surface, the gas permeability and liquid retention properties of the separator are improved, and the internal pressure during high-rate charging can be reduced.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the fibers used in the nonwoven fabric in an example of the present invention, Figure 2 is a diagram showing the relationship between nylon fiber internal porosity and liquid retention rate, and Figure 3 is a diagram showing the relationship between nylon fiber internal porosity and liquid retention rate. FIG. 4 is a diagram showing the internal pressure during charging; FIG. 4 is a diagram showing the cycle life of the nickel cadmium battery in the embodiment of the present invention; FIG.
The figure shows the 1G discharge voltage in an embodiment of the present invention.0 Name of agent: Patent attorney Toshio Nakao and one other person 3 figure o 4otoo tbo
eo. Charging electricity amount (-'/,) Fig. 4 Cycle role (Turning Fig. 5 Travel electricity amount r, x)

Claims (3)

[Claims] (1) A sealed alkaline storage battery having a group of electrode plates wound in a spiral manner with a band-shaped separator interposed between the positive and negative electrode plates, the separator being made of a non-woven fabric in which fibers are arranged irregularly, The fibers are hollow fibers with 20 to 30% pores inside, and the alkaline storage battery has fine pores on the surface that penetrate the inside. (2) The fiber is made of nylon and its apparent specific gravity is 0.
60 to 0.70, the alkaline storage battery according to claim 1. (3) The alkaline storage battery according to claim 1, wherein the fibers are made of polypropylene and have an apparent specific gravity of 0.40 to 0.60.