JPS60170159A - Seald type alkaline storage cell - Google Patents

Abstract

PURPOSE:To obtain a stable performance over a long time, in particular in a high temperature by constituting a separator using polypropylene fiber having two different diameters. CONSTITUTION:The cell uses a beltlike separator consisting of a No.1 non woven fabric 1 of polypropylene fiber 0.3-1.0 denier and a No.2 non woven fabric 2 of polypropylene fiber 2-3 denier press fitted on one or both sides of the No.1 non woven fabric. For example, the No.1 non woven fabric 1 is formed to the thickness of 0.2mm. in a fabric density of 50g/cm<2> using polypropylene fiber 0.3-1.0 denier in fiber diameter. Different from the above separator a No.2 non woven fabric 2 is formed in the fabric density of 20g/cm<2> using polypropylene fiber 2-3 denier in fiber diameter and is press fitted on both sides of the No.1 non woven fabric 1 to make a multilayer separator 3 of 0.22mm. thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to sealed alkaline storage batteries, and particularly to improvements in separators thereof.

- Conventional structure and its problems In general, an alkaline storage battery separator is placed between the positive and negative electrodes in an alkaline electrolyte to prevent contact between the two and to hold sufficient electrolyte to cause an electromotive reaction. must be able to proceed smoothly. Therefore, separators for alkaline storage batteries are required to have high alkali resistance, large electrolyte retention capacity, and sufficient resistance to external impact. In particular, in sealed alkaline storage batteries, the amount of electrolyte is set to the minimum necessary amount to ensure rapid charging performance, so a separator that can provide sufficient ionic conductivity with a small amount of electrolyte is required.

Conventionally, this type of separator is made of nylon.

Alternatively, a non-woven fabric made mainly of polypropylene fibers has been used.

Of these, nylon fiber nonwoven separators have been most commonly used in this type of sealed alkaline storage batteries, such as Hl-Cid storage batteries.

Its advantages include sufficient liquid retention due to the hydrophilic nature of the nylon fiber itself, as well as excellent gas permeability when electrolyte is present, as well as alkali resistance and oxidation resistance at high temperatures. However, it also had the disadvantage of being the main cause of deterioration of battery life.

In order to overcome the above-mentioned drawbacks of nylon nonwoven fabrics, some nonwoven fabrics based on polypropylene fibers, which have greater chemical stability than nylon over a wider temperature range, are being put into practical use. However, when polypropylene fibers are used as a constituent material of a separator, it has been said that hydrophilicity and liquid retention properties are significantly worse than those of nylon because polypropylene fibers themselves are chemically stable. In order to address this issue, (1) significantly improve the porosity and pore volume of the nonwoven fabric; (2) Adding a surfactant to improve hydrophilicity.

■By blending with nylon fiber and making a blended paper, only the advantages of each can be utilized. Such efforts are being made.

However, method (2) of increasing the pore volume of a nonwoven fabric requires that if the thickness of the nonwoven fabric is constant, the fiber density decreases, the contact area of the fiber surface with the electrolyte decreases, and the amount of electrolyte contained appears to increase, but since the holding force is small, the electrolyte may become unevenly distributed depending on charging/discharging conditions, and the probability of internal short circuiting also increases.

Furthermore, polypropylene fiber has a lower specific gravity than nylon, so if it is set to the same weight density as nylon,
As bulk density increases, gas permeability decreases. Therefore, in order to ensure gas permeability equivalent to that of nylon, the fiber weight density must be significantly lowered.Such nonwoven fabrics have extremely low strength and tend to have uneven fiber density, which can lead to internal short circuits. It was not something that could be easily done and put into practical use.

Addition of surfactant (2) makes it hydrophilic at the initial stage.

It only improves the liquid absorbency and does not completely eliminate the inherent drawbacks of polypropylene fibers.

(2) Blending with nylon fiber or mixed papermaking brings out the disadvantages of both rather than the advantages.

In other words, the liquid retention and hydrophilicity are slightly improved compared to the case of using only polypropylene fibers, but the chemical stability is rather dominated by the nylon fibers, and the advantages of polypropylene fibers are not fully utilized.

OBJECTS OF THE INVENTION The present invention aims to overcome the above-mentioned conventional drawbacks by completely improving the separator, thereby achieving stable life performance over a long period of time, especially at high temperatures.

Structure of the Invention In the present invention, a separator is constructed using two types of polypropylene fibers with different fiber diameters, and a liquid retention property equivalent to that of a nylon fiber nonwoven fabric is ensured without reducing the fiber density. That is, specifically, a first nonwoven fabric with a uniform fiber density made of ultrafine fibers of 0.3 to 1.0 denier is added to a first nonwoven fabric made of ultrafine fibers of 2 to 3 denier with a fiber density lower than that of the first nonwoven fabric made of fibers of 2 to 3 denier. This is a multi-layered separator in which the image-reduced second nonwoven fabric is integrated by pressure bonding.

Examples of stomach and light The present invention will be explained below based on Examples.

A first nonwoven fabric 1 having a thickness of 0.20 mm is formed at a fiber density of 50 ii'/m'' using polypropylene fibers with a fiber diameter of α3 to 1.0 deniers.
20 y / using 3 denier polypropylene fiber
Yy? A second non-woven fabric 2 with a fiber density of
The multilayer separator 3 shown in FIG.

The liquid retention properties and tensile strength of this separator 3 were measured and the results are shown in the following table.

In this table, nylon fiber-fed navy blue for comparison: Fabric B
, and the conventional polypropylene fiber nonwoven fabric C each have a fiber diameter of about 2 to 3 deniers.

In the table, the conventional polypropylene non-woven fabric of C is
Due to the difference in specific gravity with nylon fibers, the fiber density is reduced by approximately 16% to maintain the same porosity.

Although the Kibunmei product had a fiber weight density equivalent to that of the nylon fiber nonwoven fabric, it showed good liquid retention and Ganu permeability.

The reason why the separator of the present invention has good liquid retention properties is considered to be as follows.

That is, the liquid retention property of this type of separator depends on the inter-fiber spacing and tracheal phenomena, and is specifically determined by the fiber size and fiber density. The relationship between fiber density and liquid retention rate is shown in Figure 2, where the fiber density is 5of/yy? f changes as an inflection point.

In addition, in FIG. 2, fibers having a fiber diameter of 2 to 3 deniers were used.

The results of measuring the liquid retention rate by changing the fiber diameter of polypropylene P at this fiber density of 5oy/ynF are the third results.
It is a diagram.

As is clear from Figures 2 and 3, by setting the fiber diameter of polypropylene P to 0.2 to 1.0 denier at the fiber density of tsofli, it has a liquid retention property greater than that of nylon fiber nonwoven fabric B. .

However, the tensile strength of the nonwoven fabric C made of such polypropylene fibers is extremely low, as shown in FIG.
It is not practical. Therefore, a second non-woven fabric made of polypropylene fibers with a fiber diameter of 2 to 3 deniers is crimped to both sides of the first non-woven fabric made of polypropylene fibers of 0.2 to 1.0 denier to increase the tensile strength. The aim was to improve the

10 to 4 of this second polypropylene fiber nonwoven fabric
Fig. 6 shows the results of measuring the liquid retention property and tensile strength of the fibers by pressing them onto the first nonwoven fabric while changing the fiber density within the range of /m'.
FIG.

As is clear from FIG. 5, if the fiber density of the second nonwoven fabric is 25 f /772'' or less, it has liquid retention in the same range as the nylon fiber nonwoven fabric B.

As is clear from FIG. 6, the tensile strength was equivalent to that of nylon fiber nonwoven fabric B when the fiber density was 10 f/m' or less. In addition, the inside of the figure shows the tensile strength range of a nonwoven fabric made only of polypropylene fibers having a fiber diameter of 0.2 to 1.0 denier.

The separator of the present invention is treated with hydroxide, Ni, (OH
) 2 and a negative electrode plate mainly composed of cadmium oxide CaO and wound spirally to form a sealed *t-Ca storage battery with a capacity of 1.8 Ah.

This battery (1) has a battery port using a nylon non-woven fabric upper pallet, and a battery (3) that uses a conventional polypropylene non-woven fabric at an ambient temperature of 70°C and charges at 0.1C771A.
A cycle life test was conducted using IC771J for 16 hours and discharge, and as a result, good results as shown in FIG. 7 were obtained.

In addition, 1. It has been experimentally confirmed that a weight ratio of 2:1 to 5:1 is preferable when the second two-handed woven fabric is crimped and integrated.

In this example, the second nonwoven fabric was crimped on both sides of the first separator, but the same effect was observed even when the second nonwoven fabric was crimped on only one side.

Effects of the Invention As described above, the sealed alkaline storage battery using the separator according to the present invention can maintain good life characteristics at high temperatures.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view of a separator used in a sealed alkaline storage battery according to an embodiment of the present invention, Figure 2 is a diagram showing the relationship between fiber density and liquid retention rate in the separator, and Figure 3 is the fiber diameter of the separator. FIG. 4 is a diagram showing the relationship between fiber diameter and tensile strength. FIG. 6 is a diagram showing the relationship between fiber density and liquid retention rate of the second nonwoven fabric. 6
The figure is a diagram showing the relationship between fiber density and tensile strength of the second nonwoven fabric. FIG. 7 is a diagram showing the cycle life characteristics of a sealed alkaline storage battery using the same separator. 1...First polypropylene fiber nonwoven fabric, 2...
...Second polypropylene fiber nonwoven fabric, 3...
Separator. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 1 Figure 2, Mt. J! Ryoso 1chonomachi ('J/ga) 1m, daughter a,
Article 7 (Tenirun Figure 4) Rei 1τ counterfeit (V Rei 7th Recycle Maki (time

Claims (2)

[Claims] (1) A sealed alkaline storage battery having a group of spirally wound electrode plates with a band-shaped separator interposed between the positive and negative electrodes, the separator being made of polypropylene fibers of 0.3 to 1.0 denier. A sealed alkaline storage battery comprising a first nonwoven fabric and a second nonwoven fabric made of 2 to 3 denier polypropylene fiber, the second nonwoven fabric being crimped to at least one side of the first nonwoven fabric. . (2) The sealed alkaline storage battery according to claim 1, wherein the separator has a weight ratio of the first nonwoven fabric to the second nonwoven fabric of 2:1 to 5:1.