JPH0231462B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a sealed lead-acid battery that can improve both the discharge capacity and life of the battery, and can sufficiently prevent dilute sulfuric acid, which is the electrolyte inside the battery, from leaking out. The purpose of this study is to propose a manufacturing method for .

Conventionally, the main structure of a sealed lead-acid battery is to place a liquid-absorbing separator between the positive and negative electrodes, and to impregnate this separator with dilute sulfuric acid, which is an electrolyte, in an amount that prevents it from being freely released. .
Normally, a separator such as the one in state. It is roughly divided into two methods. In all of the methods described above, the discharge capacity of the negative electrode is larger than that of the positive electrode, and the oxygen gas generated from the positive electrode during overcharging is lost and reduced at the negative electrode and introduced into the electrolyte in the form of ions. By causing a cyclical reaction in which oxygen gas is generated from the positive electrode again, almost no waste is emitted to the outside of the battery. Of these methods,
This structure has a long lifespan because the active materials of the positive and negative electrodes are strongly compressed and held through the separator.
The composition of the electrolyte is that when it is injected into the battery, it is strongly stirred and becomes a sol-like substance due to the thixotropic phenomenon.
It has the advantage of effectively retaining the electrolyte because it fills the space between the electrode plates and between the inner wall of the electrode and the electrode plate, but it also has the effect of isolating the positive and negative electrodes and compressing and retaining the active material. It is inevitable that it will have a somewhat inferior lifespan because it has a smaller amount of energy compared to the same one.

Therefore, the present invention provides a new manufacturing method that simultaneously satisfies the advantages of the above configurations.

In addition, a separator is interposed between the positive electrode and the negative electrode to form an electrode group, and after inserting this into an electrolyte, a gel electrolyte made of dilute sulfuric acid in which silicon dioxide is dispersed is strongly stirred. The method of injecting it in the form of a sol was previously proposed by the present applicant (Japanese Patent Application No. 1983-65005).

The present invention differs from the above method in that it uses a sol in which silicon dioxide is dispersed in dilute sulfuric acid, which has sufficient fluidity without strong stirring, that is, a dilute sulfuric acid electrolyte with a low content of silicon dioxide. Features: By injecting such an electrolyte with good fluidity, the electrolyte can easily and sufficiently fill up to the pores in the battery, and the battery characteristics can be improved. Note that the injection amount of dilute sulfuric acid containing silicon dioxide is such that the liquid portion of the injected dilute sulfuric acid is preferentially absorbed by the electrode plate group including the separator, and the surrounding area of the electrode plate group, that is, the electrode plate and the inner wall of the electrode plate, is absorbed by the electrode group including the separator. Between
The amount is limited to a range in which the electrolyte present in the upper space of the electrode plate group is sufficiently gelled. If the amount of injection is too large, the electrolyte existing around the electrode plate group remains in a sol state and does not gel.

The dispersion ratio of silicon dioxide to dilute sulfuric acid is the optimum value depending on the porosity of the electrode group (liquid absorption ratio), the ratio between the electrode group and the inner wall of the electrode, the addition ratio of the dispersion liquid to the electrode group, etc. are different. However, while the dispersion is in a sol state with sufficient fluidity,
In order to form a gel state with sufficient hardness in the peripheral portion of the electrode plate group after being injected into the electric cell, a weight ratio of approximately 0.5 to 2.5% is appropriate.

Furthermore, in the present invention, when a sol-like electrolyte is injected, a part of the liquid part (dilute sulfuric acid) is preferentially absorbed into the electrode group including the separator, and as a result, the electrolyte in the area around the electrode group has a lower silicon dioxide ratio. As the amount increases, gelation is promoted. In order to continue to keep the electric cell in a sealed state, it is desirable that the positive and negative electrodes be chemically formed plates. If unformed electrode plates are used, the charging efficiency during formation is extremely low, and a considerable amount of water in dilute sulfuric acid is electrolyzed and lost, so the upper part of the electrode plate group in the electrolytic chamber is It is necessary to sufficiently increase the volume of the space to increase the amount of electrolyte injected, or to appropriately replenish water lost during chemical formation.

Next, embodiments of the present invention will be described in detail.

Chemically formed positive and negative electrodes (both are paste-type electrode plates, the positive electrode is 80mm long, 30mm wide, 3mm thick,
The negative electrode was 80 mm long, 30 mm wide, and 2 mm thick), with a separator made of 2 mm thick glass fiber mat interposed between the electrode plates, and two positive electrodes and three negative electrodes were stacked to form an electrode plate group. do. This electrode plate group was inserted into an electric cell with a margin of 1 mm on both the left and right sides of the electrode plate, and dilute sulfuric acid with a specific gravity of 1.30 in which silicon dioxide with an average particle size of 20 mμ was dispersed at 1.2% by weight was added. After injecting the solution to a depth of approximately 2 mm above the edge of the electrode plate group, the electrode was covered with a lid to seal the cell. However, the pressure inside the battery is 0.3% higher than atmospheric pressure on the lid of the battery.
A safety valve was installed that opens only when the air pressure is increased. This battery is called A. Furthermore, it was assumed here that free dilute sulfuric acid that could freely move within the battery did not actually exist.

Next, as a battery for comparison, battery B was constructed in which the electrode plate group was impregnated with dilute sulfuric acid with a specific gravity of 1.30 without silicon dioxide dispersed therein, instead of the dilute sulfuric acid in which silicon dioxide was dispersed as used in A. .
Here, the amount of dilute sulfuric acid impregnated into the electrode plate group is within a range that does not actually exist in a freely movable free state.
and in sufficient quantity.

Furthermore, while keeping the distance between the positive and negative electrodes in the electrode plate group A the same as when using a mat-like separator, the mat was removed and inserted into the electrolyte, and silicon dioxide was dispersed at 10% by weight. The dilute sulfuric acid gel having a specific gravity of 1.30 was made fluid by thixotropy while being strongly stirred, and was injected into the cell up to 2 mm above the upper end of the electrode plate group and solidified. This battery is called C.

Next, in the dilute sulfuric acid dispersion of silicon dioxide in A, the proportion of silicon dioxide was 3% by weight.
Let D be the battery in this case. In this case, it was observed that when the dispersion liquid was injected into the electrode plate, it solidified quickly, and compared to A, the penetration of the dispersion liquid into the electrode plate group was considerably hindered.

In addition, when the dispersion of silicon dioxide in dilute sulfuric acid (A) is injected into an electric chamber with a proportion of silicon dioxide of less than 0.5% by weight, the properties of the dispersion are almost the same as when dilute sulfuric acid is used alone. Almost no solidified gel-like dispersion liquid was observed around the plate group, and the amount of electrolyte solution was set to be approximately the same as in case B in order to reduce the amount of free electrolyte solution around the electrode plate group.
This battery is called E.

The batteries A to E described above were charged at a constant voltage of 2.5V (however, the maximum current was limited to 0.5A).
The figure shows the change in discharge duration when charging and discharging was repeated for 8 hours with a 2.5Ω constant resistance load until the voltage dropped to 1.75V.

According to the results shown in the figure, it can be seen that Example A has excellent discharge capacity at the initial stage of charging and discharging, and the rate of change in discharge time as the charging and discharging cycles progress is small. This is because, in A, sufficient dilute sulfuric acid is contained in the electrode group, and gel-like dilute sulfuric acid is present in the surrounding area of the electrode group, and an appropriate amount of dilute sulfuric acid is present inside and outside the electrode group. This electrolyte assists the discharge reaction, and the active materials of the positive and negative electrodes are strongly compressed by the pine-like separator, so it is thought that the decrease in discharge capacity due to repeated charging and discharging will be small. It will be done.

In B and E, the active materials of the positive and negative electrodes are strongly compressed by the pine-like separator, so there is little decrease in discharge capacity due to repeated charging and discharging, but unlike in case A, there is a gel-like diluted material around the electrode plate group. Sulfuric acid does not exist, or even if it does exist, it is very small, and the amount of sulfuric acid required for the battery reaction is insufficient and does not contribute to increasing the discharge capacity (in case of E, it contributes slightly)
It seems that this is for a reason.

In addition, in C, the active materials of the positive and negative electrodes are not strongly compressed by the pine-like separator, but are only held down by relatively soft gel-like dilute sulfuric acid, so the active materials tend to soften due to repeated charging and discharging. Therefore, it is thought that the rate of decrease in discharge capacity due to repeated charging and discharging is relatively large.

In case D, both the discharge capacity at the beginning of repeated charging and discharging and the rate of maintaining discharge capacity through repeated charging and discharging were small, but this is thought to be due to insufficient penetration of the dilute sulfuric acid sol into the electrode group. It will be done.

As explained in detail above, according to the method of the present invention, it is possible to obtain a sealed lead-acid battery with a large discharge capacity and a long life.

[Brief explanation of drawings]

The figure shows the relationship between the number of discharges and the discharge capacity of sealed lead-acid batteries according to examples of the present invention and comparative examples.

Claims (1)

[Claims] 1. A liquid-absorbing separator is interposed between the positive electrode plate and the negative electrode plate, both of which have been chemically formed, and the electrode plate group obtained by stacking the whole is inserted into an electrolyser, and then silicon dioxide is added at a weight ratio of 0.5 during the electrolyzer. By injecting a predetermined amount of highly fluid sol-like dilute sulfuric acid dispersed at ~2.5%, the dilute sulfuric acid liquid is preferentially absorbed into the electrode group, and the remaining dilute sulfuric acid existing around the electrode group is absorbed. A method for manufacturing a sealed lead-acid battery, which is characterized by gelling a dispersion liquid in which silicon dioxide is dispersed.