JPH0472352B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming a sealed lead-acid battery in a battery cell, in which the amount of electrolyte is limited and there is no free electrolyte.

Conventional Structures and Problems Sealed lead-acid batteries prevent the electrolyte from decreasing by having the negative electrode absorb oxygen gas generated from the positive electrode during charging. Therefore, a gas layer (oxygen) and a liquid layer (electrolyte) must be in contact with the negative electrode at the same time so that oxygen can be absorbed. In this state, the negative electrode is charging and discharging at the same time, so the unformed electrode plate cannot be chemically formed. Therefore, in sealed lead-acid batteries, a chemical conversion process is generally performed outside the battery case to change the positive electrode active material to lead dioxide and the negative electrode active material to lead, respectively, before battery assembly.

However, chemical conversion outside the battery case requires immediate drying treatment to prevent oxidative deterioration of the active material.
Furthermore, the battery manufacturing process is complicated, such as requiring charging for activation after battery assembly, resulting in high costs.

As a way to solve these problems, forming the electrode plates inside the battery case was proposed.

That is, a group of electrode plates consisting of an unformed positive electrode plate, a negative electrode plate, and a glass mat separator capable of holding and absorbing an electrolyte is placed in a battery case, and the battery is charged by adding electrolyte in an amount that does not allow the negative electrode to absorb oxygen gas. . After the negative electrode completes formation, the formation of the positive electrode is completed by further charging, and at the same time, the electrolyte is increased to a predetermined concentration and reduced to a specified liquid volume, increasing the oxygen gas absorption capacity of the negative electrode. .

This makes it possible to perform chemical conversion outside the container.
Immediate drying treatment and charging after battery assembly are no longer necessary. Although this was a great advantage in terms of mass production, batteries made using this manufacturing method were susceptible to overcharging due to the formation of a passive film at the interface between the positive electrode grid and the positive electrode active material. It was found that the capacity decreases early.

Purpose of the Invention The object of the present invention is to improve the overcharge resistance of a sealed lead-acid battery in which both the positive and negative electrodes are chemically formed in the battery case using unformed plates, by improving the chemical formation method.

Composition of the Invention The present invention comprises a first chemical formation step in which the positive electrode plate, which affects overcharge performance, is mainly chemically formed, and a second chemical formation step in which the negative electrode plate is formed and a predetermined electrolyte amount and concentration are achieved at the end of the formation. In the first chemical conversion step, the amount of electrolyte solution is reduced, and the chemical conversion is preferably carried out in a small amount of dilute sulfuric acid at a low concentration.

Sealed lead-acid batteries that have undergone conventional chemical formation inside the container have poor overcharge resistance, and the amount of overcharge electricity is 15 to 20 times the battery capacity (10 hour rate).
It was found that the capacity decreased. It has been found that this is due to deterioration of the positive electrode plate, and occurs because the adhesion between the positive electrode grid and the positive electrode active material decreases. The reason for this is that a large amount of a dilute sulfuric acid electrolyte of high concentration is added to perform the chemical formation in order to obtain a predetermined amount and concentration of the electrolytic solution at the end of the chemical formation. It can be assumed that if such chemical formation is performed, the adhesion between the positive electrode lattice and the active material decreases, and when a portion around the positive electrode lattice is discharged, a passive film is formed, making it impossible to discharge. Therefore, in the first chemical conversion step, the electrolyte to be injected is preferably a small amount and low concentration dilute sulfuric acid.
It has been found that it is effective to increase the degree of chemical formation (lead dioxide content in the active material) of the positive electrode plate in the first chemical formation step to 50% or more. In addition, the electrolyte in the first chemical formation process reacts with the positive and negative electrode plates to form lead sulfate after injection, so if the amount of liquid is small and the concentration is low, the electrolyte during formation will be almost neutral. As the lead becomes closer, the solubility of lead increases and becomes sulfation, which tends to cause internal short circuits. However, these problems can be prevented by adding 0.1 to 5% by weight of a neutral salt such as sodium sulfate or magnesium sulfate to the electrolyte. Also, the concentration of the neutral salt added is 0.1
If it is less than 5% by weight, there will be no effect, and if it is more than 5% by weight, the discharge capacity will decrease, which is not preferable.

The second chemical conversion step is performed continuously after the first chemical conversion step. In the first chemical formation step, the positive electrode chemical formation progress is over 50%, but the negative electrode plate absorbs oxygen gas generated from the electrode due to the low electrolyte state, and the chemical formation progress stops at around 50%. . So the second
In the chemical formation process, a higher concentration of electrolyte than that injected in the first chemical formation process is used so that the negative electrode does not absorb oxygen gas in the early stage of formation and the electrolyte reaches a predetermined amount and concentration at the end of formation. An electrolytic solution consisting of dilute sulfuric acid is added to complete the formation of the positive and negative electrode plates.

Description of Examples Specifics of a method for forming a battery case for a battery with a 10-hour rate capacity of 3Ah, in which a group of electrode plates consisting of an unformed positive electrode plate, a negative electrode plate, and a glass mat separator capable of holding and absorbing an electrolyte is housed in a battery case. An example is given below.

(First chemical conversion step) Add sodium sulfate to 16.5 ml of dilute sulfuric acid with a concentration of 10% by weight.
After pouring 0.3g of electrolyte into the battery container and closing the valve to prevent oxygen from entering the battery from outside,
A current of 0.3A is applied for 25 hours to perform chemical conversion. At this time, the degree of chemical formation of the positive electrode plate was approximately 70%.

(Second chemical conversion step) After the first chemical conversion step, the concentration of the electrolyte in the battery container is
After adding 18.9 ml of 46% by weight dilute sulfuric acid and applying a valve in the same manner as in the first chemical conversion step, a current of 0.3 A was applied for 15 hours to perform chemical conversion.

By passing through the first chemical conversion step and the second chemical conversion step, the battery container formation is completed. After completion of chemical formation, the dilute sulfuric acid electrolyte was adjusted to a concentration of 41.5% by weight and a liquid volume of 27ml. This amount of electrolyte is free of loose and free electrolyte.

Next, the results of the overcharge performance of the battery (A) produced by the chemical formation method of the present invention and the battery (B) produced by the conventional chemical formation method are shown below.

The battery produced by the chemical conversion method of the present invention has a capacity of 3Ah at the 10 hour rate shown in the example above.

On the other hand, conventional tank chemical conversion uses dilute sulfuric acid with a concentration of 31% by weight.
After adding sodium sulfate to 35.3ml and injecting it,
After installing a valve to prevent oxygen from entering the battery from the outside, the battery was charged at 0.3A for 40 hours. The amount and concentration of electrolyte after charging were the same as those of the present invention. The figure shows the change in capacity when battery A produced by the chemical formation method of the present invention and battery B produced by the conventional chemical formation process were overcharged at 0.05C (0.15A). The capacity is discharged at 0.2C (0.6A) for every 25Ah of overcharge, and the voltage decreases.
Measurements were made based on the discharge duration until the voltage dropped to 10.5V. From these results, it was found that the chemical conversion method of the present invention has significantly improved overcharge resistance performance compared to the conventional chemical conversion method. It was also found that the positive electrode plate had a high degree of chemical formation and a high capacity could be obtained in the initial stage.

Effects of the Invention According to the chemical formation method of the present invention, it is possible to significantly improve overcharge resistance, which was weak in conventional chemical formation inside the battery case, and it is also possible to reduce costs by simplifying the manufacturing process of sealed batteries. This is what I did.

[Brief explanation of the drawing]

The figure shows the capacity change due to overcharging of battery A produced by the chemical formation method of the present invention and battery B produced by the conventional chemical formation method.

Claims (1)

[Claims] 1. A separator that serves as an electrolyte absorbing and holding body;
A method for forming sealed lead-acid batteries in which the negative electrode plates are isolated and the amount of electrolyte is limited to a small amount. A first liquid injection step in which the electrolytic solution is injected into the electrode plate group, a first chemical formation step in which a charging current is applied and the electrolyte is formed, and then a diluted electrolyte with a higher concentration than the first electrolyte is formed. A closed type lead characterized by having a second injection step for supplementing a sulfuric acid electrolyte, and a second chemical conversion step in which a charging current is applied to form the electrolyte and a predetermined amount and concentration of the electrolyte are obtained at the end of the formation. Chemical formation method for storage batteries. 2. The method for chemically forming a sealed lead-acid battery according to claim 1, wherein in the first chemically forming step, the degree of chemically forming the positive electrode plate in the electrode plate group is 50% or more. 3. The method for forming a sealed lead-acid battery according to claim 1 or 2, wherein the amount of electrolyte injected in the first injection step is 30 to 70% of the electrolyte at the end of chemical formation in terms of volume ratio. . 4 The electrolyte concentration injected in the first injection process is
The method for chemically forming a sealed lead acid battery according to any one of claims 1 to 3, wherein the electrolyte has a lower concentration than the electrolyte injected in the injection step. 5. The method for chemically forming a sealed storage battery according to any one of claims 1 to 4, wherein 0.1 to 5% by weight of sodium sulfate or magnesium sulfate is added to the injected electrolyte in the first injecting step.