JPH06181068A - Sealed type alkaline storage battery - Google Patents

Abstract

PURPOSE:To improve gas absorptive characteristics by constituting a sealed type alkaline storage battery of a separator obtained by adding a surface active agent to a polyolefine porous body processed by acid having sulfate radical and a negative electrode obtained by applying water repellent resin powder to the surface when the sealed type alkaline storage battery 15 manufactured. CONSTITUTION:Polypropylene nonwoven fabric is used as a polyolefine porous body, and either one of fuming sulfuric acid, strong sulfuric acid or sulfuric anhydride is used as acid having sulfate radical, and tetrafluoroethylene- propylene hexafluoride copolymer powder is used as water repellent resin powder. Here, when the porous body is processed by the fuming sulfuric acid or the like, an electrolyte affinitive property is improved. Though a surface active agent is used in the nonwoven fabric in a manufacturing process, since this happens to be removed in the manufacturing process, an activator is added further. When electrolyte is contained in a separator abundantly, since gas absorption becomes insufficient, resin is applied, and deterioration of absorptive characteristics is restrained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline storage battery such as a sealed nickel-hydrogen storage battery or a nickel-cadmium storage battery.

[0002]

2. Description of the Related Art Alkaline storage batteries, which are widely used as various power sources, can be expected to have high reliability and can be made compact and lightweight. For this reason, small ones are used for various portable devices and large ones are used for industrial purposes. It has been used for business.

In this alkaline storage battery, an air electrode, a silver oxide electrode and the like are also taken as positive electrodes, but most of them are nickel electrodes. In addition, the characteristics of the positive electrode have been improved from the pocket type to the sintered type, and the sealing has become possible and the applications have expanded.

On the other hand, for the negative electrode, zinc, iron, hydrogen and the like are targeted in addition to cadmium as a constituent material. At present, the cadmium electrode is mainly used, but in order to achieve a higher energy density, a metal hydride, that is, a nickel-hydrogen storage battery using a hydrogen storage alloy electrode has been attracting attention,
Many proposals have been made for manufacturing methods.

As a manufacturing method for nickel electrode, cadmium electrode, hydrogen storage alloy electrode, etc., a required material is filled or applied to a porous body having a two-dimensional or three-dimensional structure such as a sintered type, a foamed state, a fibrous state or a punching metal. There is a system paste formula.

As the separator, a polyamide fiber cloth, a non-woven cloth, or a combination of these with cellophane, a polyvinyl alcohol film or the like has been adopted. Recently, fiber cloths and non-woven fabrics made of polyolefin have been partially used especially in view of alkali resistance and oxidation resistance.

In the closed type, gas permeation is necessary, so that a film-like separator is not preferable, and a non-woven fabric which is preferable in terms of impregnation with an electrolytic solution is generally used. A sealed alkaline storage battery is required to have high capacity, quick charge, long life, and the like, and improvement of the electrode active material filling property, utilization rate, gas absorption property at the negative electrode, and the like have been attempted.

[0008]

Similar to other battery systems, a sealed alkaline storage battery using a nickel electrode and a cadmium electrode or a hydrogen storage alloy electrode is also required to have high energy density, long life, and quick charge. There is.

The amount of electrolytic solution is important for high energy density, long life, and rapid charging, and it is better to have more electrolytic solution in terms of capacity and life. However, from the viewpoint of gas absorption at the negative electrode during charging, the separator needs to pass gas,
Since the electrolytic solution is used by impregnating the separator, the amount of the electrolytic solution is limited. One factor that governs the life of the sealed type is the lack of electrolyte in the separator. That is, there is no problem at the beginning of the charge / discharge cycle, but the electrode expands due to repeated charging / discharging, or the electrolyte is absorbed into the electrode due to repeated expansion and contraction, and the separator almost disappears, and therefore the internal resistance is reduced. And the voltage drops during discharge. In this case, the depletion of the electrolytic solution in the separator largely depends on the nickel electrode, and the capacity of the nickel electrode also decreases. Therefore, it suffices to increase the amount of electrolytic solution, but in the sealed type it is necessary to reach the negative electrode surface in gaseous form in order to return oxygen generated from the positive electrode in the overcharge region to water in the negative electrode, so Covering means that sealing is impossible.

In any case, the separator plays an important role in these characteristics. It is needless to say that it has low electric resistance and is excellent in alkali resistance and oxidation resistance, but it is also required to have a good impregnation property with an electrolytic solution for a longer period of time, and in the sealed type, gas permeation is required. Previously, polyamide fiber and non-woven fabrics were mainly used. However, since there are problems in terms of alkali resistance and oxidation resistance, polyolefin fiber cloth and non-woven cloth have been partially used. However, polyolefin fiber cloths and non-woven fabrics are insufficient in terms of impregnation with the electrolyte solution, and the surfactants included in the manufacturing method are inferior in electrolyte solution resistance and oxidation resistance, so they are lyophilic over a long period of time. Can't keep up. Therefore, the hydrophilicity of the electrolyte has been improved by treating the polyolefin porous body with fuming sulfuric acid or concentrated sulfuric acid, but it was still insufficient.

The present invention has been made in consideration of the above-mentioned conventional problems, and an object of the present invention is to provide a sealed alkaline storage battery having excellent gas absorption characteristics, high capacity and long life.

[0012]

In order to achieve the above-mentioned object, a sealed alkaline storage battery of the present invention comprises a separator obtained by adding a surfactant to a polyolefin porous body treated with an acid having a sulfate group, and a surface thereof. The negative electrode is formed by applying a water-repellent resin powder to.

In this case, a polypropylene non-woven fabric is used as the polyolefin porous body, and fuming sulfuric acid, concentrated sulfuric acid, or sulfuric acid is used as the acid having a sulfate group, and 4-fluoroethylene- is used as the water-repellent resin powder to be applied to the negative electrode. A propylene hexafluoride copolymer powder is preferable.

[0014]

In the separator of the sealed alkaline storage battery having the above structure, the hydrophilicity of the electrolyte is improved because the polyolefin porous body is treated with fuming sulfuric acid or concentrated sulfuric acid. This is probably due to the formation of sulfone groups in the polyolefin. Thereafter, a surfactant is added to this. Nonwoven fabrics made of polyethylene or polypropylene are included in these commercially available nonwoven fabrics because a surfactant is used in the manufacturing process thereof as described above. However, since the polyolefin is destroyed during the treatment with fuming sulfuric acid or concentrated sulfuric acid, and a washing process is also included, the surfactant is removed. The treatment with the sulfuric acid group alone cannot provide a sufficient amount of the electrolyte solution, which requires a balanced amount of electrolyte solution. That is, a large amount of electrolytic solution is contained in the separator to improve discharge characteristics and life. On the other hand, when a large amount of the electrolytic solution is contained in the separator, oxygen from the positive electrode hardly permeates through the separator during overcharge, and gas absorption in the negative electrode during rapid charge becomes insufficient. Therefore, since the surface of the negative electrode is coated with the water-repellent resin powder, it is possible to suppress the deterioration of the gas absorption characteristics.

[0015]

EXAMPLE An example of the sealed alkaline storage battery of the present invention will be described below. Commercial thickness 0.15 mm, porosity about 6
A 0% polypropylene non-woven fabric is immersed in concentrated sulfuric acid containing 5% fuming sulfuric acid for 7 minutes at room temperature. Remove the sulfuric acid with a centrifuge, wash with water and dry. This treatment changes the non-woven fabric from white to light brown. A 0.1% aqueous solution of a neutral surfactant on the market was added thereto, and the mixture was heated and dried at 100 ° C. to obtain a separator.

Next, a hydrogen storage alloy electrode will be taken as an example of the negative electrode. One of the LaNi ₅ type alloys, MmNi _3.7 , Mn
_{After 0.4} , Al _0.3 , and Co _0.6 were crushed and passed through 300 mesh, a 5 wt% fluororesin dispersion solution was added so that this resin would be 1.5 wt% with respect to the hydrogen storage alloy powder. Make a paste. This paste is then applied with a thickness of 0.17 mm, a hole diameter of 1.8 mm and an opening degree of 5
It was applied to a perforated metal plate made of 3% iron and plated with nickel, and smoothed through a slit of 0.6 mm. This electrode is cut into a width of 33 mm and a length of 210 mm,
The lead plate was attached by spot welding. The electrode was first pressed with a press of 100 t and then further adjusted with a roller press to a thickness of 0.52 mm. Then, 0.5 to 0.6 mg / cm ² of commercially available tetrafluoroethylene-6 fluoropropylene copolymer powder was applied on the electrode surface.

A known foamed nickel electrode was used as the nickel electrode, and 30 g / 1 of lithium hydroxide was dissolved in an aqueous caustic potash solution having a specific gravity of 1.30 as an electrolyte to form a sealed nickel-hydrogen storage battery. . Battery is SubC
It is a type. This battery is designated as A.

Next, for comparison, a battery in which a surfactant was added to the separator and the water-repellent resin was omitted from the negative electrode was B. The addition of the surfactant to the separator was omitted and the water-repellent resin was applied to the negative electrode. Was added as C.

First, the initial discharge voltage and capacity were compared. When 10 cells were used at a constant current charge of 0.2 C at a constant current charge of -1 C and discharged at a constant current of 0.9 V up to 0.9 V, the average voltages A and B were 1.20 V and C was slightly inferior. 1.19 V, discharge capacity A and B are 2.78 to 280
Ah and C were 2.75-2.78 Ah.

Next, 10 cells of each battery were used to compare the life characteristics. Charging / discharging was repeated under the conditions of constant current charge of 120% of capacity at 0.5 ° C. at 20 ° C. and discharge to 0.9 V at −0.5 C. 10 cycles each for 10 cycles
When it was set to 0, A averaged 98% at 400 cycles, whereas B averaged 95% and C averaged 92%. A was 92% in 800 cycles, while B was B.
Was 89% and C was 82%. Thus, A was excellent in terms of life.

Finally, the rapid chargeability was investigated. Ambient temperature 3
First, at 0.7 ° C, when 0.7C was charged, the capacity was 150
% When the battery is charged, the pressure inside the battery is 1.3 Kg / cm ² , B
Is 3.9 Kg / cm ² , C is 1.8 Kg / cm ² , then A is 3.1 Kg / cm ² and B is 8.
It was 5 Kg / cm ² and C was 3.7 Kg / cm ² . Thus, A was also excellent in terms of gas absorption.

[0022]

As is clear from the description of the above embodiment,
The present invention uses a separator formed by adding a surfactant to a polyolefin porous body treated with an acid having a sulfuric acid group such as fuming sulfuric acid or concentrated sulfuric acid, and a negative electrode coated with a water-repellent resin powder on the surface of a gas. It is possible to obtain a sealed alkaline battery that has a long capacity and shows a high capacity without deterioration of absorption characteristics.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoichiro Tsuji 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A separator obtained by adding a surfactant to a polyolefin porous body treated with an acid having a sulfate group,
A sealed alkaline storage battery having a negative electrode having a surface coated with a water-repellent resin powder. 2. The sealed alkaline storage battery according to claim 1, wherein the acid having a sulfate group is fuming sulfuric acid, concentrated sulfuric acid, or anhydrous sulfuric acid. 3. The sealed alkaline storage battery according to claim 1, wherein the polyolefin porous body is a polypropylene nonwoven fabric. 4. The water-repellent resin powder is 4-fluoroethylene-
The sealed alkaline storage battery according to claim 1, which is a powder of a hexafluoropropylene copolymer.