JPH05307971A - Sealed lead-acid battery - Google Patents

Abstract

PURPOSE:To increase the discharging capacity and prevent the formation of layers and improve liquid pouring property by packing and putting a mixed powder of a water-repelling powder and a hydrophilic powder having high liquid retaining property as an electrolytic liquid retaining material in the gap between electrode plates and the periphery of a group of electrodes. CONSTITUTION:Besides powders of polyethylene resin, polypropylene resin, and fluororesin which have water-repelling property themselves, a powder coated with a powder of a resin which is sulfuric acid-resistant and is not harmful to a battery or a powder such as a silica powder which has water-repelling property polyethylene resin can be used as a water-repelling powder. A group of electrode plates prepared by assembling positive poles 2 and negative poles 3 while a separator 4 being set between a positive pole and a negative pole is inserted in an electrolytic bath 1 and the bath is filled with a mixed powder 5 consisting of 10% by volume of hydrophilic silica powder and the water-repelling powder while vibration is applied to the bath. Being pressed by a finely porous rubber plate 7, the resulting body is sealed with a cover 6 having projections. Diluted sulfuric acid which makes the electrolytic liquid specific weight 1.30 at 20 deg.C after chemical conversion is poured in the bath and chemical conversion is carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed lead-acid battery, and more particularly to an improvement in an electrolytic solution holder thereof.

[0002]

2. Description of the Related Art There are two types of sealed lead-acid batteries, a retainer type and a gel type, in which a negative electrode absorbs oxygen gas generated during battery charging. The retainer type inserts a mat-shaped separator (glass separator) mainly composed of fine glass fibers between the positive electrode plate and the negative electrode plate, which holds the sulfuric acid electrolyte necessary for discharge and separates both electrodes. In recent years, it has been widely used as a backup power source for portable devices and computers by taking advantage of its features such as no maintenance, no leakage, and position-free.

However, the glass separator is made of a fine glass fiber having a diameter of about 1 micron manufactured by a special method into a mat, and is considerably expensive as compared with a commonly used lead-acid battery separator. Moreover, in order to obtain stable battery performance, the electrode plate group must be strongly pressed and assembled, which makes it difficult to assemble the battery, which inevitably increases the manufacturing cost of the battery.

Further, the sulfuric acid electrolytic solution can be held only by the glass separator inserted between the positive and negative electrode plates, and the electrolytic solution is placed around the electrode plate group like an open type lead acid battery. Since the batteries cannot be arranged, the battery reaction is limited by the amount of the electrolytic solution, and the battery performance is inferior to that of the liquid battery.

On the other hand, although the gel type is less expensive than the retainer type, it has a drawback that the battery performance is inferior to the retainer type and the life performance is not good because the electrolytic solution separates from the sulfuric acid gel during use.

In order to solve these drawbacks, therefore, there has been proposed a sealed lead-acid battery which is neither a retainer type using fine glass fibers nor a gel type using a gel electrolyte. That is, a powder having a high porosity and a large specific surface area, for example, silica powder, is used as the electrolyte holding material, and the powder is filled in the gap between the positive electrode plate and the negative electrode plate and around the electrode plate group. It is a sealed lead-acid battery with a configuration.
Silica powder, which is called white carbon, is an inexpensive material that is produced and sold in large quantities and has excellent acid resistance and electrolyte retention, so it is the electrolyte retention material for this type of sealed lead-acid battery. It can be said that it is an excellent material as a powder used for.

The sealed lead-acid battery using such silica powder as an electrolyte holder also has the same problem as the conventional sealed lead-acid battery. That is, the diffusion rate of the electrolytic solution is much slower than that of the open type liquid battery, and the utilization rate of the electrolytic solution is low. This is a phenomenon that occurs because the electrolyte is made non-fluidized. Further, such a sealed lead-acid battery has a smaller absolute amount of electrolytic solution than the open type, and improvement of the utilization rate of electrolytic solution is a proposition.

Therefore, in order to increase the utilization rate of the electrolytic solution,
For example, a method such as coarsening the glass fiber in the retainer system, a method such as lowering the gel concentration in the gel system,
In a battery that uses powder for holding electrolyte, there is a method of increasing the diffusion moving speed of electrolyte by increasing the diameter of powder and widening the gap between powders. According to the method, a difference in specific gravity occurs in the vertical direction of the battery accordingly, and a so-called stratification phenomenon becomes a problem.

In the case of an open type liquid battery, the stratification phenomenon can be prevented by stirring the liquid by gassing during charging of the positive and negative electrode plates, but the negative electrode plate absorbs oxygen gas generated during charging of the battery. In the sealed lead-acid battery, the specific gravity of sulfuric acid becomes high in the lower part of the battery due to gravity. When the concentration of sulfuric acid becomes high, the negative electrode plate is difficult to be charged, and by repeating charge and discharge, lead sulfate, which is a discharge product of the negative electrode active material, accumulates in the lower part of the negative electrode plate, and the negative electrode plate deteriorates, so that the battery discharge capacity becomes early. Will fall.

Furthermore, when a powder having a high electrolyte absorbing property is applied to a battery in which silica powder is used as an electrolyte holder, the following phenomenon occurs at the time of liquid injection. When the required amount of electrolyte is poured from the top of the battery into the battery, first the electrolyte is absorbed by the upper surface of the powder,
Thus, a powder layer containing the electrolytic solution is formed. This layer hinders the exhaust of air from the inside of the battery, making it difficult for the electrolytic solution to permeate to the lower part of the battery, and it takes a long time to inject the electrolytic solution.

Therefore, a method of injecting the electrolytic solution after depressurizing the inside of the battery can be considered. Even if the inside of the battery is depressurized, if diluted sulfuric acid as the electrolytic solution is injected, the electrolytic solution comes into contact with
Carbon dioxide gas is generated by reacting with basic lead carbonate contained in the active material. The exhaust of the generated carbon dioxide gas was hindered by the layer containing the electrolytic solution formed on the upper part of the powder, and the injection time was not significantly shortened.

[0012]

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems, and the gist thereof is a sealed lead-acid battery in which powder between the electrodes and around the electrodes is subjected to a water-repellent treatment. A mixed powder of a powder whose body or powder itself is water-repellent and a hydrophilic powder such as silica is filled and arranged, and a sufficient amount of sulfuric acid electrolytic solution necessary for discharging is added to the above mixed powder and a separator. And to impregnate and hold the positive and negative electrode plates.

[0013]

EXAMPLES The present invention will be described below based on examples.
As the powder having water repellency, four types of powder shown in Table 1 were used. Resin powder with water repellency is polyethylene resin,
As the fine powder of polypropylene resin and fluororesin, which was subjected to the water-repellent treatment, silica powder covered with fluororesin was used. The particle size of these powders is
50-500 microns. In addition to these powders, a powder of a resin having sulfuric acid resistance and not harmful to the battery, a powder of silica, or the like whose surface is coated with a substance having water repellency may be used.

A method for treating silica powder with water repellent using a fluororesin will be described below. First, the silica powder was washed with acetone and dried. This powder was immersed in an organic solvent in which a fluororesin was dissolved and then dried to obtain a powder in which the surface of silica powder was covered with a fluororesin film. These powders were mixed with hydrophilic silica powder in a volume ratio of 10% by volume to obtain mixed powders shown in Table 1.

[0015]

[Table 1]

A battery test was conducted using these powders. FIG. 1 is a cross-sectional view of a sealed lead-acid battery of the present invention, in which a positive electrode grid body made of an antimony-free lead alloy or a lead alloy containing a small amount of antimony and a negative electrode grid body made of an antimony-free lead alloy are used in a normal positive electrode and a negative electrode. After filling and aging the paste, two positive electrode plates 2 and three negative electrodes 3 were formed.
An electrode plate group constructed by assembling via the separator 4 was produced using the sheet and the sheet, and was inserted into the battery case 1.

Then, only the mixed powders A to D and the silica powder are densely filled in the battery case in which the electrode plate group is inserted while vibrating, and the powder is scattered and blown up on the filled powder upper part. In order to prevent this, a microporous rubber plate 7 having open cells was placed. In the figure, 5 is powder, 6 is a lid of the battery case, 8 is a protrusion provided on the inner surface of the lid 6 for holding the microporous rubber plate 7, and 9
Is a positive electrode terminal, and 10 is a negative electrode terminal. Here, the mixed powder A
B to D were used as batteries A to D, a battery using only silica powder was used as a battery E for comparison, and a battery filled with powder having a large particle size was used as a battery F.

To the battery thus assembled, diluted sulfuric acid adjusted so that the specific gravity of the electrolytic solution after formation was 1.30 at 20 ° C. was injected to perform formation. The capacity of this prototype battery is limited by the electrolytic solution, and the nominal capacity is 5 Ah. For comparison, a retainer-type sealed lead-acid battery G using a glass separator made of fine glass fibers was also manufactured using the same lot of electrode plates.

The initial capacities of these seven types of batteries were discharged at a current of 5 hours, and the terminal voltage was 1.75 V per cell.
The time to reach was measured. The discharge capacities at this time are shown in Table 2, and the time required for injecting the electrolytic solution into these batteries is also shown. After that, fill in the following contents
A discharge cycle life test was conducted.

Discharge: discharge to 1.70 V with current at a rate of 5 hours Charge: charge 120% of the discharged electricity amount at a rate of 10 hours The life was judged to be 50% or less of the nominal capacity. After that, the battery was disassembled and the cause of the end of life was investigated. The results are shown in Table 2.

[0021]

[Table 2]

Regarding the injection time, only the glass separator using the glass separator did not require 1 minute for injection. The injection time of the batteries A to D according to the present invention and the battery F using the coarse powder of the prior art was about 2 minutes, which was longer than that of the glass separator, but about 35 minutes using only the silica powder. Very short compared to. This is considered to be because the gas stored in the lower portion of the container could be discharged to the upper space through the air layer formed on the surface of the water repellent powder by using the powder mixed with the water repellent powder. It is considered that the reason is that because the powder having a large particle size was used, the gap between the powders was wide, and the gas could be quickly discharged to the upper part through the gap. It is considered that this is because the glass separator has a large space between glass fibers and a large gas escape path.

The batteries A to D according to the present invention and the battery F using the coarse powder of the prior art have an initial capacity of about 10% higher than other batteries, which improves the utilization rate of the electrolytic solution. It is thought that it is because I did it. Regarding the life performance, the battery F using the coarse powder has a capacity of 50% or less at the 121th cycle, and the retainer battery G also has a life at the 152th cycle. The batteries A to D and the battery E are 2
Excellent life performance was exhibited at 40 cycles or more.

After the life test, when the battery was disassembled, a large amount of lead sulfate was accumulated in the lower half of the negative electrode plate of the battery F using the powder having a coarse particle size, and also in the retainer battery G, A large amount of lead sulfate was accumulated in about 1/3. This is
It is speculated that stratification of the electrolytic solution caused the life of the two batteries.

When the difference in the distribution of the electrolytic solution in the vertical direction of the electrolytic solution holding material was investigated, the concentration of the electrolytic solution was low in the upper part and high in the lower part. In the batteries A to D according to the present invention, such a phenomenon was not observed, and the deterioration of the positive electrode plate directly caused the life.

This is because in the mixed powders A to D, the weakly held electrolytic solution of the mixed water-repellent powders having an excellent diffusivity leads to an improvement in the initial capacity and the capacity during the cycle, It is considered that the electrolytic solution that strongly holds the silica powder prevented stratification. In the case of using only silica powder, it is considered that the holding capacity is too strong, which leads to a decrease in the utilization rate of the electrolytic solution, and the initial capacity is lowered.

In the case of using the retainer type and the powder having a coarse particle size, it is considered that the holding force of the electrolytic solution is weak and the electrolytic solution is stratified because the gap between the particles or the fibers is large. ..

[0028]

As described above, a water-repellent powder or a mixed powder of a water-repellent powder obtained by subjecting a powder to water-repellent treatment and a hydrophilic powder having a large liquid-holding property is used as an electrolyte solution holding material. By using it, the discharge capacity of the battery can be increased, stratification can be prevented, and a battery excellent in liquid injection can be manufactured, and its industrial value is very large.

[0029]

[Brief description of drawings]

[0030]

FIG. 1 is a sectional view of the sealed lead-acid battery of the present invention.

[0031]

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery case 2 Positive electrode plate 3 Negative electrode plate 4 Isolator 5 Powder 6 Lid 7 Microporous rubber plate 8 Protrusion 9 Positive electrode terminal 10 Negative electrode terminal

Claims (1)

[Claims] 1. A sealed lead acid battery in which an oxygen gas generated during charging of the battery is absorbed by a negative electrode, wherein a water-repellent powder and a hydrophilic powder having a large liquid absorbing property are provided between electrode plates and around an electrode group. A sealed lead-acid battery characterized by filling and arranging a mixed powder with the body, and impregnating and holding a sufficient amount of sulfuric acid electrolyte necessary for discharging into the mixed powder, the separator and the positive and negative electrode plates. ..