JP4390735B2 - Method of manufacturing electrode plate for lead acid battery and lead acid battery - Google Patents

Description

The present invention relates to a method for manufacturing a lead storage battery, particularly an electrode plate, and relates to a method for manufacturing an electrode plate that can suppress a decrease in chemical conversion efficiency.

Conventionally, a lead-acid battery plate is manufactured by filling a lead alloy grid with a paste-form active material in which lead powder composed of lead oxide and metal lead, water, dilute sulfuric acid, and if necessary, reinforcing materials such as fibers are kneaded. , Drying (temperature 150 to 250 ° C.), aging (temperature 40 to 80 ° C., humidity 90 to 99%), and drying (temperature 50 to 80 ° C.) to produce an unformed paste-type electrode plate. Drying before aging is performed in order to promote the oxidation reaction in the aging process by setting the water content in the paste-like active material within a predetermined range (hereinafter, drying before aging is referred to as pre-drying in the present application). Call). Before carrying out preliminary drying, the electrode plate after filling with the paste-like active material is immersed in sulfuric acid, sulfates, water, etc., or by spraying these aqueous solutions, a lead sulfate layer or basic lead sulfate on the electrode plate surface. Forming a layer or the like (hereinafter referred to as a lead sulfate layer), further strengthening the bonding between the particles and preventing cracks on the electrode plate surface (hereinafter referred to as lead sulfate by dipping or spraying) In some cases, the step of forming the layer is referred to as soaking.

The main component of the active material for a lead storage battery is lead monoxide (PbO), also called resurge, and contains metallic lead (Pb). The paste obtained by kneading these lead powder and dilute sulfuric acid maintains moderate hardness and shear strength in combination with excessive PbO. During aging, the lead in the lattice undergoes lead oxidation and lead sulfate crystal growth.

In recent years, lead-acid batteries capable of high output have been developed for lead-acid batteries, and studies have been made to increase the number of electrode plates stored in the battery by thinning the electrode plates and to improve current collection efficiency. ing. In order to realize such a battery, it has moderate hardness due to the formation of a thin active material layer / lead sulfate layer and lead sulfate on the surface of the electrode plate, thereby preventing cracks on the electrode plate surface and dropping of the active material. There is a need.

For example, a paste is filled in a grid to prepare an electrode plate, and the electrode plate is passed through a pair of soaking rolls containing dilute sulfuric acid on the surface before the preliminary drying step, so that dilute sulfuric acid is applied to the electrode plate. Then, the electrode plate is passed between a pair of rolls rotating in the direction opposite to the traveling direction of the electrode plate to smooth the surface of the electrode plate (Patent Document 1), or from a Pb-Ca alloy The lattice active material is filled with a paste active material, and dilute sulfuric acid is sprayed on both sides of the electrode plate during the aging process, so that the formation of the lead sulfate layer is reduced to zero. It has been proposed that an appropriate amount of moisture is supplied into the electrode plate, the lattice body and the active material are sufficiently adhered, and the active material is prevented from falling off the electrode plate (Patent Document 2).
JP-A-9-92269 Japanese Patent Laid-Open No. 2002-8644

However, when dilute sulfuric acid is applied to the electrode plate by the roller method before the preliminary drying step as in the method described in Patent Document 1, a relatively large amount of dilute sulfuric acid contained in the soaking roll is supplied to the electrode plate, so It is difficult to form a thin lead sulfate layer, and the layer is formed unevenly. This has the effect of preventing surface cracks during pre-drying, but in the chemical conversion process, if the lead sulfate layer is thick or non-uniform, lead sulfate, which is a non-conductor, is also present inside the electrode plate as a layer. As a result, there is a problem that the chemical conversion efficiency is lowered and the initial capacity of the lead storage battery is difficult to be obtained. In the method described in Patent Document 2, since dilute sulfuric acid is sprayed on the surface of the electrode plate, it is possible to form a thin lead sulfate layer (the formation of the lead sulfate layer is zero or less). Since it was spraying, cracks on the surface of the electrode plate, the soaking effect, were not suppressed. In addition, since pre-drying is not performed after spraying with dilute sulfuric acid, the amount of water contained in the paste does not decrease, resulting in a decrease in chemical conversion efficiency.

Under such a background, a method for producing an electrode plate for a storage battery that prevents cracking that occurs on the surface of the electrode plate by soaking and that does not reduce the formation efficiency by forming a thin lead sulfate layer is provided. It is hoped to do.

In the present invention, after filling a substrate made of a lead alloy with a pasty active material, the surface is sprayed with a dilute sulfuric acid aqueous solution having an average particle diameter of 10 to 20 μm by a laser diffraction method and then passed through a predrying furnace. It is characterized by.

In the present invention, the average particle diameter in which the dilute sulfuric acid aqueous solution is sprayed is suitably in the range of 10 to 20 μm, and the lead sulfate layer can be formed as thin and uniform as about 10 to 125 μm. Then, since preliminary drying is performed quickly, the water content in the paste-like active material can be set within a predetermined range. Therefore, the aging reaction is not delayed in the aging step performed after the preliminary drying step. However, when the average particle size to be sprayed is 20 μm or more, the lead sulfate layer becomes 150 μm or more, and not only the lead sulfate layer cannot be formed thin, but also the reaction time is delayed in the aging process, and the aging process is prolonged. It is necessary and not industrially preferable. Further, when the average particle diameter to be sprayed is 10 μm or less, the lead sulfate layer can be formed as thin as 10 μm or less, but since the lead sulfate layer is too thin, the soaking effect is hardly seen.

In addition, the present invention allows a dilute sulfuric acid aqueous solution to pass through a drying furnace immediately after spraying. However, when natural drying is performed without using a drying furnace, the thickness of the lead sulfate layer is not uniform, and the amount of moisture in the paste It takes a long time to obtain a predetermined water content, which is not industrially preferable. Further, when aging without drying after diluting an aqueous solution of dilute sulfuric acid, the amount of water in the paste is large, and in the subsequent aging process, oxygen permeation is hindered and sufficient crystal growth does not proceed. -There is a possibility that the adhesion at the substrate interface may be reduced.

In the laser diffraction method used in the present invention, when spray particles are present on the laser beam path, the laser beam is scattered on the particle surface, and measurement is performed by applying a diffraction image behind it by interference of scattered light. Is.

In the method for producing an electrode plate for a lead storage battery according to the present invention, the soaking after filling the substrate with the paste-like active material is performed by spraying a dilute sulfuric acid aqueous solution having an average particle size of 10 to 20 μm. Thus, it is possible to provide a good electrode plate that is thin and uniform, does not cause cracks on the surface of the substrate, and does not lower the formation efficiency. Moreover, the lead storage battery excellent in the initial stage discharge capacity can be provided by using the electrode plate produced by this invention.

An embodiment of the present invention will be described with reference to FIG. Although the present invention can be applied to both positive and negative plates, the positive plate will be described below.

FIG. 1 is an explanatory view showing an embodiment of the present invention. An electrode plate 3 in which a positive electrode paste-like active material is applied to a substrate made of a lead alloy is placed across two chain belts 4 and sprayed. 1 is conveyed. The conveyed electrode plate 3 is sprayed on the front and back surfaces of the electrode plate 3 by dilute sulfuric acid mist 13 ejected from a nozzle 12 disposed in the center of a spraying device 11 disposed in the upper and lower centers of the spray chamber 1. A lead sulfate layer (not shown) is formed on the front and back surfaces of the electrode plate. Thereafter, the electrode plate 3 is transported from the spray chamber 1 to the preliminary drying furnace 2 by two chain feed belts 4 and dried. Thereafter, aging is performed.

The upper nozzle of the nozzle 12 disposed at the center of the spraying device 11 disposed at the upper and lower center of the spray chamber 1 is directed directly below, and the lower nozzle is sprayed on the dilute sulfuric acid mist 13 directly above. A thin layer of lead sulfate can be formed on the front and back surfaces of the electrode plate 3 by dilute sulfuric acid mist 13 ejected from above and below. Three nozzles 12 arranged at the upper and lower centers of the spray chamber 1 are arranged in a straight line at equal intervals in a direction perpendicular to the conveying direction of the electrode plate 3, and the dilute sulfuric acid mist 13 to be sprayed is mutually connected. It was made not to overlap and to be able to spray evenly on the front and back surfaces of the electrode plate 3 so that there was no gap. In addition, it is preferable to spray the dilute sulfuric acid aqueous solution on the entire surface of the electrode plate by changing the number of nozzles used depending on the size of the electrode plate. The nozzle is a fan-shaped nozzle, and the dilute sulfuric acid mist ejected from the nozzle is ejected so that the air pressure is 0.2 MPa and the spray pattern draws a fan shape. The inside of the spray chamber 1 is normal temperature. In the present invention, a nozzle for drawing a fan-shaped spray pattern is used, but a nozzle for drawing a circular or square spray pattern may be used.

A grid substrate obtained by casting with a known lead alloy is filled with a positive electrode paste-like active material, and a dilute sulfuric acid aqueous solution with a specific gravity of 1.15 is sprayed on the front and back surfaces of the electrode plate by the spray device described in the above embodiment. Thereafter, preliminary drying was performed in a 170 ° C. atmosphere using a preliminary drying apparatus. Thereafter, aging was performed in an atmosphere of 50 ° C. and 98% humidity for 30 hours, followed by drying at 70 ° C. for 2 hours to produce a positive electrode unformed electrode plate. A negative electrode non-formed electrode plate was also produced in the same manner. These unformed electrode plates are alternately stacked with 8 positive electrodes and 9 negative electrodes with a mat-like separator made of glass fiber to produce a group of electrode plates, housed in a battery case, and covered with the battery case. Was given. Thereafter, dilute sulfuric acid having a specific gravity of 1.20 (20 ° C.) was injected, and the battery case was formed for 40 hours to produce a sealed lead-acid battery of 2V-200 Ah.

When the particle diameter of the sprayed particles of the dilute sulfuric acid aqueous solution in the above-described example was measured by a laser diffraction method, the average particle diameter was 10 μm (present product 1). In the above embodiment, the average particle size of the spray particles was measured in the same manner by changing the nozzle, and diluted sulfuric acid mists having average particle sizes of 15 μm (product 2 of the present invention) and 20 μm (product 3 of the present invention) were obtained. Similarly, a sealed lead-acid battery of 2V-200 Ah was produced by spraying.

(Comparative example)
The spray particles of the dilute sulfuric acid aqueous solution were 2 V in the same manner as in Example except that the particle diameter was 5 μm (Comparative Example 1), 25 μm (Comparative Example 2), 50 μm (Comparative Example 3), and 100 μm (Comparative Example 4). A sealed lead-acid battery of −200 Ah was produced.

(Conventional example 1)
A sealed lead-acid battery of 2V-200 Ah was produced in the same manner as in the example except that after the dilute sulfuric acid aqueous solution was sprayed on the front and back surfaces of the electrode plate and preliminary drying was not performed (conventional example 1).
(Conventional example 2)
A sealed lead-acid battery of 2V-200 Ah was produced in the same manner as in Example except that the dilute sulfuric acid treatment was performed using a soaking roll (Conventional Example 2).
(Conventional example 3)
A sealed lead-acid battery of 2V-200 Ah was produced in the same manner as in Example except that dilute sulfuric acid treatment (soaking) was not performed (Conventional Example 3).

Table 1 shows the conversion efficiency when each sealed lead-acid battery is formed into a battery case. In addition, chemical conversion efficiency is shown by the PbO ₂ conversion rate which is a positive electrode active material.

As shown in Table 1, Inventions 1 to 3 and Comparative Example 1 were able to obtain the same chemical conversion efficiency as that of Conventional Example 3 in which soaking was not performed, and could prevent a decrease in chemical conversion efficiency associated with soaking. In Comparative Examples 2 to 4 and Conventional Examples 1 and 2, the chemical conversion efficiency decreased. Therefore, when the lead sulfate layer formed on the surface was measured, the present inventions 1 to 3 were 125 μm or less, while the comparative examples 2 to 4 and the conventional example 2 were 150 μm or more. In particular, the conventional product 2 was partially formed deeply into the interior. In this way, since the lead sulfate layer is thick, the chemical conversion efficiency decreases in Comparative Examples 2 to 4 and Conventional Example 2. Moreover, although the comparative example 1 can obtain the chemical conversion efficiency equivalent to this invention 1-3, it is necessary to perform the spraying time to the electrode plate of dilute sulfuric acid aqueous solution for a long time, and is not industrially preferable. Further, as in the case of the conventional product 1, when the pre-drying is not performed after the dilute sulfuric acid aqueous solution is sprayed, the moisture contained in the paste does not decrease. Crystal growth did not progress, and the adhesiveness at the paste-substrate interface was lowered.

Furthermore, the initial discharge capacities when the sealed lead-acid batteries produced using Inventions 1 to 3, Comparative Examples 2 and 4 and Conventional Products 1 and 3 were discharged at discharge currents of 20, 46 and 200 A, respectively, were measured. Table 2 shows the initial discharge capacity at that time.

As shown in Table 2, it can be seen that the present inventions 1 to 3 have superior initial discharge capacities as compared with Comparative Examples 2 and 4. This is because the decrease in chemical conversion efficiency is suppressed and the amount of residual lead sulfate is large. In addition, in Conventional Example 1 in which preliminary drying was not performed after spraying with a dilute sulfuric acid aqueous solution, the adhesiveness at the paste-substrate interface was lowered as compared with the first to third aspects of the present invention, and the active material was detached. Further, since the conventional example 3 was not soaked, cracks occurred on the substrate surface along the lattice during preliminary drying, and the initial capacity was significantly reduced.

From the above results, it is possible to form a thin lead sulfate layer by spraying a dilute sulfuric acid aqueous solution having an average particle size of spray particles of 10 to 20 μm on the surface by a laser diffraction method. . In addition, a sealed lead-acid battery with improved initial discharge capacity can be provided.

Explanatory drawing which shows embodiment of this invention.

DESCRIPTION OF SYMBOLS 1 Spraying chamber 11 Spraying device 12 Nozzle 2 Pre-drying furnace 3 Electrode plate 4 Chain belt

Claims (2)

It is characterized in that after a paste-form active material is filled in a substrate made of a lead alloy, the surface is sprayed with a dilute sulfuric acid aqueous solution having an average particle diameter of 10 to 20 μm by a laser diffraction method and then passed through a predrying furnace. A method for producing a lead-acid battery electrode plate. A lead-acid battery using an electrode plate obtained by the method according to claim 1.