JPS5929365A - Manufacture of paste type positive plate for lead storage battery - Google Patents

Abstract

PURPOSE:To improve the life characteristic by immersing a supporter in acid solution such as acetic acid, nitric acid to dissolve the lead oxide layer on the surface then applying lead paste on the supporter adhered with solution. CONSTITUTION:The surface of a supporter made of lead alloy is oxidized to PbO. The surface of paste material or lead powder is also oxidized to PbO. When immersing the supporter into acid solution for dissolving lead oxide, metal lead is exposed on the surface. When applying paste on the supporter adhered with solution, lead oxide in the paste is dissolved in said solution to expose metal lead on the paste face contacting with the supporter. Consequently metal lead on the surface of the supporter will contact with metal lead in the paste to improve the tightness thus to suppress deterioration of initial capacity in slow discharge cycle.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to improvements in lead-acid batteries, and more particularly to improvements in the manufacturing method of paste-type positive electrode plates.

Conventional configuration and problems Paste type electrode plates have the advantage of being inexpensive and having a high utilization rate. However, it has the disadvantage of poor longevity characteristics. In particular, in recent years, low-antimony and even antimony-free lead alloys have been studied in order to make them maintenance-free, and lead-calcium alloys have come to be used as supports. However, compared to the conventional lead-antimony alloy, the lead-cal/ium alloy has worse cycle life characteristics. In particular, the final voltage is 1.7 at a current rate of 6 to 10 hours.
Repeated deep discharges of 5V had the disadvantage that the capacity rapidly decreased with each cycle.

This is thought to be caused by the interface between the support and the active material, but the detailed mechanism is not clear.

However, it can be inferred as follows. That is, the oxide film of the lead-calcium alloy is dense and easily peels off.

In the active material of the electrode plate using the conventionally used lead-antimony alloy, comparatively inert a P bo2 is easily generated compared to the case where the lead-Cal/Rum alloy is used. As described above, in an electrode plate using a lead-calcium alloy, the oxide film formed on the surface of the support peels off, and cracks tend to occur at the interface between the support and the active material. Furthermore, since the active material near the support contains a lot of active β-PbO2, when electric discharge is performed, the dilute sulfuric acid impregnated in the cracks reacts with the active material, resulting in Pb
SO4 is generated. Since this PbSO4 is in a passive state, it is thought that the reaction ends when the support is surrounded by a passive layer of PbSO4. Therefore, when charging and discharging cycles are repeated, cracks increase at the interface between the support and the active material, and P
It is thought that a passive layer of bSO4 is more likely to be formed and the discharge capacity is reduced.

Therefore, a method of covering the surface of the support with an active material has been considered in order to reduce the area where the support comes into contact with the electrolytic solution to delay the formation of an oxide film or to reduce cracks. By this method, the slow discharge cycle characteristics could be improved in many ways.

In addition, it is known that a-PbO2, which is relatively inert, is easily generated when the sulfuric acid concentration is low, so a method is adopted in which the electrolyte concentration is adjusted to, for example, 20% by weight or less at the end of discharge. It is being

This is because since charging occurs near the support, a large amount of inert α-PbO2 is produced in the active material near the support, which has the effect of suppressing passivation near the support.

The above measures are used to suppress early capacity deterioration. However, the capacity deterioration is still greater than that of an electrode plate using a lead-antimony alloy.

Purpose of the Invention The present invention suppresses early capacity deterioration during slow discharge cycles caused by the interface between the support and the active material, and in particular improves the life characteristics of maintenance-free lead-acid batteries using lead-calcium alloys. The purpose is to achieve this goal.

Structure of the Invention The present invention uses lead oxide (pbo) such as acetic acid or nitric acid as a support.
The lead oxide layer on the surface of the support is dissolved by immersing it in an acidic solution that dissolves lead oxide, and then a lead paste is applied to the support with the solution already deposited.

The surface of the support made of lead alloy is exposed to Pb due to oxygen in the air.
Oxidized to O. Lead powder, which is still a raw material for paste, has metallic lead in its center, but its surface 1l-iPbQ
is oxidized to Generally, the degree of oxidation is 6o to 8oφ. Therefore, when the support is immersed in an acidic solution that dissolves lead oxide as in the present invention, the thin film of lead oxide covering the surface of the support is dissolved, and metallic lead is exposed on the surface. Next, when a paste is applied to the support coated with the solution I, the lead oxide in the paste I dissolves in this solution, and metallic lead is also exposed on the paste surface that has come into contact with the support. Therefore, the metal lead on the surface of the support comes into contact with the metal lead in the paste, and the adhesion between the support and the paste becomes strong, thereby making it possible to suppress early capacity deterioration during slow discharge cycles.

As described above, the present invention is characterized in that a paste is applied to a wet, crumbly support coated with a solution of acetic acid, nitric acid, etc. that dissolves lead oxide. Here, when drying after immersion, an oxide film is generated again and the adhesion with the active material is improved.
However, unlike the present invention, it is not seen to be as drastic as in the present invention. / Kota,
When the support is immersed in the solution, unevenness may appear on the surface of the support due to local differences in dissolution rate, and the effect of this surface condition may suppress capacity deterioration to some extent.

On the other hand, according to the present invention, it is possible to achieve a stable and significant improvement.

Although there is no need to particularly regulate the immersion time in the solution of the present invention, it is preferably within 1 hour. That is, the oxidized layer on the surface of the support is completely dissolved in about 5 to 16 seconds after immersion. Even if the support was removed before the oxidized layer was completely dissolved, the oxide layer would be dissolved in the liquid adhering to the support, so even a few seconds of immersion would be effective. on the other hand,
The effects of the present invention can be obtained even when immersed for a long time. However, when using a liquid that also dissolves metallic lead, such as nitric acid, the support will gradually dissolve, so long-term immersion must be avoided. Particular care must be taken when using a lightweight and thin support. The dissolution rate of lead-calcium alloy in nitric acid aqueous solution is
When the support 36y having a thickness of 1.0 was immersed in 10% nitric acid for 1 hour, it was about 0.37 (just under 1 inch). Therefore, a short period of immersion is sufficient, but if immersed for a longer period of time, it is better to do it within one hour.

Note that the solution used is generally a solution in which acetic acid or nitric acid dissolves lead oxide. The effect can be obtained when the concentration ranges widely from 0.1 to 1oot4. However, if the ratio is less than 1, the effect tends to decrease slightly. On the other hand, when the concentration is high, it is effective for the main purpose of the present invention, which is to suppress early capacity deterioration, but it has the negative effect of accelerating corrosion of the support. There were cases where the cycle life was reached. Therefore, the preferred concentration is 1 to 2
0 weight person.

DESCRIPTION OF EMBODIMENTS Next, the features of the structure and effects of the present invention will be described with reference to embodiments.

Expanto metal of Pb-(0.5% by weight) Sn(0, 4% by weight) Ca alloy was used as the support.

First, an acetic acid aqueous solution (10% by weight) and a nitric acid aqueous solution (10% by weight) were prepared. The support was immersed in each aqueous solution, taken out after 1 minute, and the paste was applied to the support wet with the aqueous solution. Each battery A was made using the positive electrode plate made in this way.

A positive electrode plate was made using this support, and a battery C was obtained.

Further, after being immersed in the acetic acid aqueous solution, the positive electrode plate was washed with water, and the positive electrode plate was suspended using the wet support to form a battery cell. Furthermore, as a comparative example, Battery E was made using a support that was not immersed in a solution. In addition, for the negative electrode plate, a support that was not immersed in a solution was used for each battery.

The charge/discharge cycle characteristics were investigated for the five types A to H above. The battery was discharged at 5A until the voltage reached 1.7V, and charged at 3A for 13 hours. This charging and discharging was defined as one cycle, and charging and discharging were repeated. Then, the discharge time of the first cycle is 5.
The life cycle is determined when the cycle becomes 0% or less. The results are shown in the figure. As is clear from the figure, battery A is manufactured by the manufacturing method of the present invention.

Compared to Comparative Example E, Sample B had significantly improved capacity deterioration and achieved 30 cycles or more. Comparative Example C was slightly better than E, but did not have a large effect. On the other hand, as in the present invention, when the support was in a wet state and the solution was different, there was little effect as the result of cell plating was poor.

From the above two results, is it possible to use a solution that dissolves lead oxide as in the present invention? When the paste is applied to the support, the metal lead is exposed on both the support and the paste, and as they come into contact with each other, the adhesion is increased and the interface is strengthened, which increases the capacitance. It is thought that this will significantly improve deterioration. However, as can be seen from the results of Example 1, the effect is drastically reduced when the support is dried after being immersed.

This is thought to be because an oxide film is formed again by drying, and the main effect of the present invention is lost.

However, small irregularities on the surface of the support due to immersion seem to have some effect. In addition, battery glue is used by dissolving the oxide film on the support, washing it with water, and using the support in a wet state. In this case, it is considered that the surface of the support is oxidized and most of the metal lead is exposed. However, even with this alone, the effect of suppressing capacity deterioration is smaller than that of battery C.

This is thought to be caused by the water layer having an adverse effect, but the details are not clear. However, when a solution that dissolves lead oxide was used as in the present invention, there was a significant effect on capacity deterioration. This seems to be because, even though the solution layer has a slight negative effect on the scale like the aqueous layer, it has a much greater effect of strengthening the interface due to contact between the metallic lead.

Although the solution concentration and immersion time were not described in the examples, similar effects were obtained up to a concentration of 1 to 10%. However, the soaking time is also 2 if the bone thickness of the support is 1.5 mm.
Although the investigation was conducted up to o hours, the present invention was effective in suppressing early capacity deterioration. However, when nitric acid is used, approximately 50% of the support is dissolved in 20 hours, and considering this point, 1
It is preferable to do it within hours.

Effects of the Invention As described above, according to the present invention, early capacity deterioration during slow discharge cycles caused by the interface between the support and the active material can be suppressed.

This early capacity deterioration is particularly noticeable when a lead-calcium alloy is used for the support. Therefore, by solving this problem, it will be possible to make lead-acid batteries maintenance-free.

[Brief explanation of drawings]

The figure shows the cycle characteristics of lead-acid batteries using various positive electrodes. Heri^'s outfit 4 Rigo Ko Aki W and others fR3 JP-A-59-29365 (4)

Claims (3)

[Claims] (1) A method for producing a paste-type positive electrode plate for a lead-acid battery, which comprises applying a solution that dissolves lead oxide to a support, and applying lead paste to the support while wet with the solution. (2) The method for producing a paste-type positive electrode plate for a lead-acid battery according to claim 1, wherein the step of applying the solution to the support comprises immersing the support in a solution that dissolves lead oxide. (3) A method for manufacturing a paste-type positive electrode plate for a lead-acid battery according to claim 1 or 2, wherein the support is a lead-calcium alloy.