JP2002231234A - Method of preparing paste active material for use in positive electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of preparing the paste active material for use in a positive electrode capable of manufacturing a control valve-type lead-acid battery having high ratio of PbO2 in battery case formation, high capacity and a long service life. SOLUTION: A kneaded matter is prepared by kneading lead powder and dilute sulfuric acid, and left standing in an atmosphere of 70-95 deg.C and 80-98% relative humidity for four hours or more. Then the kneaded matter after left standing, is stirred to prepare the paste active material for the positive electrode containing 67% or more tetrabasic lead sulfate of 5-50 μm to be used in a positive plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a paste active material for a positive electrode used in a control valve type lead-acid battery.

[0002]

2. Description of the Related Art A control valve type lead-acid battery is widely used for an uninterruptible power supply, a battery for an automobile, and the like because of its features of being inexpensive and having high reliability. In the control valve type lead-acid battery, a paste-like active material is filled in a grid made of a lead alloy, aged and dried to prepare unformed paste-type positive and negative electrode plates.

[0003] The positive electrode plate and the negative electrode plate are laminated via a retainer and welded to form an electrode plate group. The electrode plate group is inserted into a battery case and hermetically sealed. It is common to manufacture. Recently, there has been a strong demand for cost reduction, high capacity, and long life of these control valve type lead storage batteries.

[0004] Here, in order to reduce the cost of the lead-acid battery of the control valve type, it is necessary to reduce the charge amount at the time of forming the battery case;
That is, it is effective to increase the PbO ₂ conversion rate (chemical charging efficiency) with a small amount of charge.

[0005] As a method of reducing the amount of charge at the time of forming a battery case, a method of adding lead in a paste active material for a positive electrode has already been used. Then, by causing conductive lead dioxide generated by the reaction of lead red and sulfuric acid to be present in the paste-like active material for the positive electrode, the conversion rate of PbO ₂ during the formation of the battery container has been improved.

On the other hand, as a technique for extending the life of a control valve type lead-acid battery, lead powder and diluted sulfuric acid are kneaded to prepare a positive electrode paste active material, and the positive electrode paste active material is made of a lead alloy. After filling the lattice body to form a positive electrode plate, a method of aging the positive electrode plate in a high-temperature and high-humidity atmosphere to prepare a positive electrode plate containing tetrabasic lead sulfate in an active material has been used. .

[0007]

However, in the method using a large amount of lead tin, although the PbO ₂ conversion rate during the formation of the battery container is improved, the life is shortened at an early stage, and an unfavorable tendency is recognized.

On the other hand, in a positive electrode plate aged at high temperature and high humidity, it is difficult to control the size of tetrabasic lead sulfate in the active material. When the tetrabasic lead sulfate in the positive electrode active material grew to a thickness of 80 to 100 μm, there was a problem that the conversion rate of PbO ₂ and the discharge capacity during the formation of the battery container were reduced.

The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-mentioned problems. A paste for a positive electrode capable of producing a control valve type lead-acid battery having a high conversion rate of PbO ₂ during formation of a battery case and having a high capacity and a long life is provided. An object of the present invention is to provide a method for producing an active material.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, a first invention comprises a step of kneading lead powder and dilute sulfuric acid to prepare a kneaded material, and the step of kneading the kneaded material at a temperature of 70 to 95. ° C,
The method according to the second aspect of the present invention is characterized in that the method further comprises a step of leaving the mixture in an atmosphere having a relative humidity of 80 to 98% for 4 hours or more, and a step of stirring the kneaded material after the leaving. 67% by mass of tetrabasic lead sulfate of 5 to 50 μm
It is characterized by being stirred so as to exist.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Production of Control Valve Type Lead-Acid Battery Several kinds of positive electrode paste active materials produced by various methods described below were used. Then, 150 g of the paste-like active material for each positive electrode was added to ^w 70 mm × ¹ 190 mm × ^t
A 3.5 mm lead-calcium alloy lattice was rubbed and filled, left in an atmosphere of 35 ° C. and 90% relative humidity for 20 hours, and dried at 60 ° C. for 72 hours to produce an unformed positive electrode plate. On the other hand, as a negative electrode plate, ^w 70 × ^l 190 ×
The conventional one with a ^{t of} 2.5 mm was used.

An electrode group is assembled by laminating and welding four of the above-described positive electrode plates and five of the conventionally used negative electrode plates via a glass fiber retainer. AB
After assembling into an S container, a dilute sulfuric acid electrolyte having a concentration of 28% by mass was injected. The components, assembling conditions, and the like of the control valve type lead storage battery other than the positive electrode plate are the same as those in the related art.
2. After testing the control valve type lead-acid battery, the battery was charged at 0.23 CA (8.2 A) for 44 h in a water tank at 40 ± 5 ° C. to form a battery case, and then the specific gravity of the electrolyte was reduced to 1.26 (20 ° C.). This was adjusted to produce a control valve type lead-acid battery having a nominal capacity of 35 Ah-2V.

After the formation of the battery case, a part of the lead-acid storage battery was disassembled, the positive electrode plate was taken out, and the conversion rate of PbO _{2 in} the active material of the positive electrode plate, which was used to judge the chemical conversion, was measured. The remaining control valve type lead-acid battery was discharged at 25 ° C. and 3.5 A (0.1 CA) (discharge end voltage: 1.8 V), and the initial discharge capacity was measured.

After that, each of the produced control valve type lead-acid batteries is
A cycle life test was performed in which a pattern of discharging at 2 ° C. and a constant current of 8.75 A (0.25 CA) for 2 hours and charging at 3.5 A (0.1 CA) constant current for 6 hours was one cycle at 5 ° C.
The discharge capacity of the control valve type lead-acid battery is changed every 50 cycles.
Discharged to a final voltage of 1.8 V at a constant current of 3.5 A (0.1 CA) and measured, and the discharge capacity was 70% of the nominal capacity.
The point in time when (25Ah) was not reached was defined as the life. In addition, the cycle test was continued on the control valve type lead storage battery which has not reached the life under the conditions described above.

[0015]

Embodiments of the present invention will be described below in detail. Examples 1 and 2 and Comparative Examples 1 to 3 As an example of the present invention, a paste-like active material for a positive electrode was produced by the method shown in FIG. That is, 100 parts by mass of lead powder containing lead monoxide as a main component is put into a kneading device at room temperature, and sulfuric acid 1 having a concentration of 35% by mass
5 parts by weight and an appropriate amount of water are added and kneaded to prepare a paste-like active material. Then, the paste-like active material is placed in a thermo-hygrostat at a temperature of 80 ° C. and a relative humidity of 90%, respectively.
It was left for 2 hours, 4 hours, and 8 hours.

On the other hand, as Comparative Example 1, a paste-like active material which was not left in the constant temperature and humidity chamber was also prepared. Thereafter, the above-mentioned five types of paste-like active materials were each stirred for 5 minutes to prepare a paste-like active material for a positive electrode.

A positive electrode plate using the positive electrode paste active material was prepared by the above-described method, and a control valve type lead-acid battery was prepared using the positive electrode plate and tested. The details of the production conditions and test conditions of the control valve type lead-acid battery are as described above.

The prepared control valve type lead storage battery is formed into a battery case,
Table 1 shows the measurement results of the PbO ₂ conversion ratio, the initial discharge time, and the cycle life after the battery case formation. From Table 1, it can be seen that the use of the present invention can extend the life, although the PbO ₂ conversion ratio and the initial discharge time after battery case formation are slightly inferior to those of Comparative Example 1.

[0019]

[Table 1]

(Examples 1, 3 to 5) Next, the paste-like active material for the positive electrode was produced by the method shown in FIG. 1 while changing the stirring time after standing. That is, 100 parts by mass of lead powder mainly composed of lead monoxide is put into a kneading apparatus at room temperature, and 15 parts by weight of sulfuric acid having a concentration of 35% by mass and an appropriate amount of water are added and kneaded to prepare a paste-like active material. I do.

The paste-like active material is heated at a temperature of 8
It was stored in a thermo-hygrostat at 0 ° C. and a relative humidity of 90% for 4 hours. Then, 5, 10, 15, 20, 30,
The mixture was stirred for 40 minutes to prepare a paste-like active material for a positive electrode. The size of the tetrabasic lead sulfate in the positive electrode paste active material after stirring was SEM (S-3500N type, manufactured by Hitachi, Ltd.), and its content was determined by an X-ray diffractometer (MXP3 type, manufactured by Mac Science). Was measured.

A positive electrode using the above-mentioned paste active material for a positive electrode
A plate is created in the manner described above, and a control valve is
A lead-acid battery is prepared, and the initial discharge capacity and P
bO ₂The conversion was measured. The production of a control valve type lead-acid battery
Details of the conditions and test conditions are as described above.

The produced control valve type lead storage battery is formed into a battery case,
Table 2 shows the results of measuring the conversion rate of PbO ₂ , the initial discharge time, and the life after formation of the battery case. From Table 2, when the amount of 5 to 50 μm tetrabasic lead sulfate in the paste-like active material is increased to 70% or more by optimizing the stirring time, the conversion rate of PbO ₂ is high and the initial discharge capacity is excellent. I understand.

[0024]

[Table 2]

In the above embodiment, the temperature is 80 ° C.
An example in which the relative humidity was left at 90% was shown.
Almost the same effect was obtained when the device was left at -95 ° C and the relative humidity was 80-98%. In addition, although lead powder was used in the above-described embodiment, substantially the same effect was obtained when lead tin was added to the lead powder.

[0026]

As described above, when the present invention is used, it is possible to provide a method for producing a control valve type lead-acid battery having a high conversion rate of PbO ₂ , a high capacity and a long service life when forming a battery case. It is excellent.

[Brief description of the drawings]

FIG. 1 is a method for producing a paste-like active material for a positive electrode according to the present invention.

Claims (2)

[Claims] 1. A process for preparing a kneaded product by kneading lead powder and dilute sulfuric acid, and leaving the kneaded product in an atmosphere at a temperature of 70 to 95 ° C. and a relative humidity of 80 to 98% for 4 hours or more. And a step of stirring the kneaded product after standing. 2. The paste-like active material for a positive electrode, comprising:
2. The method for producing a paste-like active material for a positive electrode according to claim 1, wherein the mixture is agitated such that 0 μm of tetrabasic lead sulfate is present in an amount of 67% by mass or more.