JPS58175260A - Chemical conversion of pastey lead storage battery - Google Patents

Abstract

PURPOSE:To enhance greatly the cycle life characteristic of a plate by maintaining the rapid electric-discharge and regulate the early reduction in capacity of the plate by converting chemically only the lower part of the plate in an aqueous weakly acidic, neutral-salt or alkaline solution, and adding dilute sulfuric acid after that. CONSTITUTION:In a chemical conversion process carried out by feeding current to a plate after pouring dilute sulfuric acid used as an electrolyte after the plate is inserted in the container, before adding dilute sulfuric acid, below 10% of the theoretical capacity of electricity is fed by adding an aqueous solution with an acidified degree of over pH 3 until a part of the plate is immersed, and thereafter the usual chemical conversion with added dilute sulfuric acid is carried out. Although there is an active part in the upper part of the plate, differently from such a conversion that is carried out by feeding current after the whole of a plate is immersed in an aqueous neutral-salt or alkaline solution, the rapid electric-discharge characteristic naturally decreases as the part of the plate immersed in the solution is increased, and the slow electric-discharge life tends to deteriorate as the part immersed in the solution is decreased. Therefore, it is preferred that 1/5-3/4 of the plate is immersed in the solution. In addition, in order to prevent any marked reduction of the slow electric-discharge capacity although depending upon the depth of immersion, it is preferred that the quantity of electricity fed to the plate in the preliminary chemical conversion is suppressed to around 0.01-10% of the theoretical capacity of the plate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming paste-type lead-acid batteries, and particularly aims to maintain rapid discharge characteristics and improve life characteristics.

Paste type lead-acid batteries have a high utilization rate and can be manufactured at relatively low cost, and are the most commonly used among lead-acid batteries. Historically, paste-type batteries have had a deep connection with the development of the automobile industry, so efforts have been focused on improving the startup characteristics, or rapid discharge characteristics, and efforts have been focused on improving the charge-discharge cycle, which has a relatively short lifespan. It's been directed at me. However, in recent years, the uses of batteries have become more diverse, and with the addition of devices that require slow discharge and deep discharge for automobiles, achieving both slow discharge life characteristics and rapid discharge characteristics has become an important issue. It is. However, approaches that pursue both of these properties include, for example, porosity, α-Pb02/
β-pbo, ratio etc. and lifespan.

The relationship between utilization rate and rapid discharge characteristics is well known, and it is difficult to obtain satisfactory results.

The present invention provides one means for effectively improving these problems, specifically.

A neutral aqueous solution such as sodium sulfate or lithium sulfate or an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide is applied to a state where a portion of the lower part of the electrode plate is immersed, and an amount of electricity of 10% or less of the theoretical capacity is applied. It is characterized in that it is then chemically formed in dilute sulfuric acid.

In relation to these techniques, the present inventors have particularly focused on Pb-C
In order to suppress the early capacity deterioration phenomenon caused by slow discharge, which tends to occur with so-called lead-calcium alloys such as A-AN, a short-time chemical conversion treatment is performed in a neutral or weakly alkaline electrolyte. The authors proposed that the above-mentioned process of immersion in a neutral or alkaline aqueous solution for a short period of time should be carried out prior to chemical formation in normal dilute sulfuric acid. It is assumed that at least the shoulder of the electrode plate is submerged in the aqueous solution.In contrast, in the present invention, the electrode plate is not completely immersed, but is immersed to the extent that a portion of the bottom is submerged. In other words, in the former case, the entire electrode plate is coated with an untreated plate (a paste made mainly of lead powder, sulfuric acid, and water) and dried in a neutral or alkaline bath. The plate) is first oxidized from the vicinity of the lattice, and the α-
The idea is to preferentially form Pb02 at the interface between the lattice and the active material, and then slowly form highly reactive β-Pb02 offshore in dilute sulfuric acid. For applications where deep discharge does not occur, we were able to find conditions that pose no practical problems by limiting the amount of current applied in the neutral or alkaline solution to a certain extent. ) On the other hand, in the latter case, in the present invention, by solving such an interface problem, the next cause that becomes apparent is the softening and falling off of the active material itself, and this is especially true during long-term cycles. The difference in concentration and temperature between the top and bottom of the liquid in the battery has a direct and indirect effect on the
Focusing on the tendency for deterioration to concentrate in the lower part, the aim is to unevenly distribute active materials with different utilization rates within the board surface, especially in the upper part. ib, here, weakly acidic.

By applying an oxide layer containing a large amount of α-PbO2, which is generated by energization in neutral or alkaline conditions, to some extent on the active layer rather than simply on the lattice interface, the layer is made resistant to softening and falling off. Further, the amount thereof is controlled by the amount of electricity supplied, and the uneven distribution position is generally preferentially determined by the depth of direct immersion into the liquid from the bottom due to the structure of the battery.

Fortunately, the capillary action of the liquid to the upper part, which is not immersed in the upper part, is due to the neutrality or alkalinity necessary for the preferential production of α-Pb02 at the lattice interface mentioned above. This allows the preliminary chemical solution to be supplied, and since there is a large impedance difference between the ion conduction path and the immersed part, even if the upper and lower sides are energized at the same time, α- PbO2 will be distributed.

If the above treatment is followed by conventional chemical formation in dilute sulfuric acid, active β-Pb02 will be distributed in the upper part, which has a high contribution rate to sudden discharge, and α-Pb02, which is resistant to softening, will be distributed in the lower part where deterioration is likely to occur. Moreover, the entire structure has a lattice interface structure that suppresses early deterioration.

As is already clear here, the present invention differs from those in which the electrode plate is immersed 100% in a neutral salt or alkaline aqueous solution to conduct electricity, in that the electrode plate has an active part on the upper part. Naturally, as the part immersed in the liquid becomes larger, the rapid discharge characteristics will deteriorate.
Furthermore, as the immersion area decreases, the slow discharge life tends to deteriorate. this thing.

Therefore, preferably 175 to 3/4 of the electrode plate is immersed.

Also, although it depends on the immersion depth, it is better to suppress the amount of current during preliminary formation to about 0.01 to 10% of the theoretical capacity of the electrode plate, so that the gradual discharge capacity does not decrease significantly. Although a long energization time is good for the lifespan, it is better to keep it to one hour or less in order to suppress slow discharge: a decrease in the initial value of the capacity.

The concentration of neutral salts and alkaline aqueous solutions is 0.1 for neutral salts.
Effects can be obtained at ~10% by weight, but preferably 0.5~10% by weight.
Stable properties can be obtained at 5% by weight.

For alkali, 0.01 to 10% by weight and α-PbO2
Although the concentration required to form ゜ is expanded to a lower region,
Substantially, stable effects can be obtained at about 0.02 to 1% by weight.

As described above, by chemically forming only the lower part of the electrode plate in a weakly acidic salt or alkaline aqueous solution, and then adding dilute sulfuric acid, rapid discharge characteristics can be maintained, early capacity loss can be controlled, and cycle life characteristics can be improved. Significant improvements can be made.

The structure and effects of the present invention will be described below with reference to Examples.

Expand lead-calcium alloy to 10x10cr
A support was prepared by cutting it into pieces of n size, and a paste was applied to the support to make an electrode plate. Using this electrode plate, a battery with six positive electrodes and six negative electrodes was constructed. This battery contains 20% of Na2804.
q/Q aqueous solution M and NaOH (7) 5g/Q aqueous solution B was added so that the entire surface of the electrode plate was immersed (M1,
B1') and 374 of the polar plate (Mu2, B2).

172 (mu 3.B3) of the electrode plate, 174 (mu 4゜B) of the electrode plate
For each item a) is soaked in, 1
The current was applied in the charging direction for 2 minutes at a current of 100 Ω.

After that, add dilute sulfuric acid adjusted to have a sulfur brewing specific gravity of 1.20 so that the liquid volume becomes 75Qcc, and continue to add 1o
The chemical formation was carried out by applying current for 5 hours in a vacuum chamber. As a comparative example, a battery C was prepared which was formed by adding dilute sulfuric acid with a specific gravity of 1.20 from the beginning.

Using the above battery, it was discharged for 160 μm at -15°C.

Figure 1 shows 1. It shows the duration until OV. As is clear from the figure, the battery group 3°B3. of the present invention. M4. B4
showed the same characteristics as C without chemical conversion treatment. Mu2. B2
1. is slightly worse, but the whole surface is chemically treated. Better than B1. Also, when comparing Na2 SO4 aqueous solution M and NaOH aqueous solution B, M is slightly better. This is thought to be because the alkaline aqueous solution has a stronger effect and therefore has a stronger influence on the active material.

Next, the nine types of batteries described above were newly made and subjected to a JIS life test of discharging at 20 m for 1 hour and charging at 6 m for 6 hours, and the cycle in which the battery became less than 40% of the initial capacity was defined as the life. Figure 2 shows the results.

As is clear from the figure, 1. the method of the present invention; 2. B2. M3゜B
3. M4. B4 was the best, followed by Mu1., which had its entire surface chemically treated. It was B1. C without chemical conversion treatment reached the end of its life after 8o cycles. It is thought that Battery C had poor cycle characteristics because it reached the end of its life due to the same cause as early capacity deterioration due to insulation at the interface between the support and the active material.

This can be inferred from the fact that when observing the electrode plate after its life, there is no apparent abnormality in the electrode plate. In addition, batteries that underwent chemical conversion treatment reached the end of their lifespan due to short circuits caused by softening and falling off of the active material.

In addition, 1. A battery in which the lower part of the electrode plate of the present invention is chemically formed is a battery in which the entire surface is preformed. The reason why the life characteristics are superior to B1 is thought to be that although the support interface is strengthened throughout the electrode plate as described above, the effect on the active material is different.

That is, when discharging a constant amount of electricity as in the JIS life test, in the battery of the present invention, the upper part of the electrode plate contains active β-P.
b02, and since α-PbO2 is contained in the active material in the lower part, it is thought that the upper part reacts preferentially. Therefore, the reaction in the lower part of the electrode plate, which is vulnerable to life expectancy, is alleviated and deterioration is suppressed. On the other hand, in a battery that has undergone chemical conversion treatment on the entire surface, relatively inert α-PbO2 is scattered in the active material over the entire surface of the electrode plate, and when a certain amount of electricity is discharged, the entire surface reacts in the same way.
It is thought that relatively inactive α-PbO2 gradually changes to active β-PbO2 through repeated charging and discharging. Therefore, the lower part of the electrode plate is not immediately preserved, and it is thought that the lower part of the electrode plate softens and falls off earlier than in the case of the present invention in which only the lower part is subjected to chemical conversion treatment, resulting in the end of its life.

On the other hand, in the example, an example was described in which the product was immersed up to 1/4, but the immersion amount up to 1/6 is sufficiently effective in improving the life. If it is less than 1/6, the effect will be drastically reduced, which is not preferable.

In the above example, an expanded lead-calcium alloy, which has a drawback in capacity deterioration, was used as the support, but it is also possible to use a commonly used cast grid of lead-antimony alloy as the support. It was confirmed that it is effective in improving JIS life characteristics.

As described above, the present invention significantly improves cycle life characteristics, maintains rapid discharge characteristics with relatively simple operations, and suppresses early capacity deterioration.

[Brief explanation of the drawing]

FIG. 1 shows a comparison of discharge duration during rapid discharge of batteries with different formation conditions, and FIG. 2 shows a comparison of cycle life characteristics. Name of agent: Patent attorney Toshio Nakao and 1 other person11
Figure 2rI! J

Claims (1)

[Claims] (1) In the chemical formation process in which an electrode plate is inserted into a battery container, dilute sulfuric acid as an electrolyte is added thereto, and electricity is applied, an aqueous solution with a pH of 3 or more 6 is applied to the electrode plate before adding dilute sulfuric acid. After adding electricity until it is partially immersed and applying an amount of electricity less than 10% of the theoretical capacity,
A method for forming a paste-type lead-acid battery, which is characterized by ordinary chemical formation with the addition of dilute sulfuric acid. (2) The method for chemically forming a paste type lead-acid battery according to claim 1, wherein the aqueous solution is a neutral aqueous solution of sulfate. (3) The method for forming a paste type lead-acid battery according to claim 1, wherein the aqueous solution is an alkaline aqueous solution. G4) The immersion ratio of the electrode plate in the aqueous solution is 176 to 3/4
A method for chemically forming a paste type lead-acid battery according to any one of claims 1 to 3. (6) The method for chemically forming a paste type lead-acid battery according to claim 2, wherein the concentration of the neutral aqueous solution is 0.1 to 10% by weight. (@ The concentration of alkaline aqueous solution is 0.01 to 10% by weight
A method for forming a paste type lead-acid battery according to claim 3.