JPH07118321B2 - Lead acid battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement of a lead storage battery, and in particular, a reticulated body is formed from a sheet-shaped lead alloy by machining,
It improves the reliability of lead acid batteries used as a grid.

Conventional technology In lead-acid batteries, in recent years, instead of the casting-type grid body that has been developed for 100 years, a mesh-like body is formed from a sheet-shaped lead alloy by mechanical processing such as expanding and punching, and this grid is formed. The technology used for is emerging. The reason is that in addition to the fact that it is rich in continuous production and extremely high in productivity, it has changed from an alloy system containing antimony with a good hot water flow, which has been mainly used in the past, to an alloy system containing no antimony. This is because it is easy to adapt to the transition of. In other words, in order to achieve both strength, corrosion resistance, and productivity by using calcium, strontium, or appropriate tin instead of antimony with a low hydrogen overvoltage, a new method of processing from the above alloy sheet that is not affected by melt flow is It will be extremely suitable.

Problems to be Solved by the Invention However, some practical problems have occurred very recently in adopting these construction methods. First, there is a decrease in service life when used at high temperatures, and secondly, there is corrosion in the vicinity of the joint between the ears of the current collector and the strap. For automotive starting, which is the largest demand for lead-acid batteries, the temperature inside the bonnet has recently tended to rise. Corrosion phenomena peculiar to the negative electrode occur in the former, especially in the positive electrode, and in the latter, not only the positive electrode but also the negative electrode. is doing. Furthermore, this phenomenon frequently occurs in which corrosion occurs early when a non-antimony lattice is processed from a sheet and used only for the negative electrode system.

The present invention is a recent problem that occurs in the peculiarity of using a sheet of lead alloy to form a mesh to form a mesh and using it as a lattice and the peculiarity of not containing antimony in the alloy sheet, that is, improving the life even at high temperature and especially in the negative electrode. It is intended to suppress the unique corrosion phenomenon of.

Means for Solving the Problems As a specific means for solving the above problems, in the present invention, a lattice body formed by machining a cold-rolled alloy sheet does not contain antimony, and calcium, tin, and selenium are included. And a lead alloy containing bismuth is used.

Action In the present invention as described above, the life characteristics are recognized extremely remarkably at a high temperature, and especially from the recent tendency of 70.
It is remarkable in the range over 80 ℃. The mechanism of suppressing the high temperature deterioration is considered as follows. First, the reticulate body obtained by machining from a sheet form has a smooth sheet surface and cut surface, a small bonding area with the active material, and a small bonding strength. Therefore, in the general conventional usage, the bone was wrapped with the active material in a sandwich form by overpasting, which was sufficiently practical. However, in recent years, the tendency of higher temperature is 70 ° C rather than 70 ° C, and the oxidation, deformation and elongation of the lattice are extremely increased. On the other hand, selenium refines the crystal of the sheet-like alloy to improve its own oxidation resistance, and at the same time, the resistance to the elongation of the lattice increases. Further, the adhesion of the oxide layer on the surface of the lattice formed by repeated charging and discharging to the lattice is increased as compared with the case where selenium is not added. This tendency becomes more remarkable when bismuth is present in the lattice alloy. Even if the amount of bismuth present is as small as 0.01% by weight or less, it is effective.

The use of an alloy containing antimony in this configuration is not only basically unsuitable for seeking maintenance-free properties, but the hardness of the sheet-shaped alloy after it is manufactured is not only strong but is gradually softened and re-solidified. Due to the phenomenon, it becomes practically impossible to endure the expanding process. This effect is remarkable in the case of an alloy containing calcium or tin in which casting crystals become relatively large, and lead-calcium and lead-calcium-tin alloy sheets, which are commonly used in maintenance-free batteries, are extremely effective. . Further, although it is often formed into a sheet by cold rolling, although the hardness is increased on one side by cold rolling, the drawback that the oxidation resistance is lowered is suppressed by the addition of selenium.

Note The amount of these, 10 ^-3 to 10 ⁰ percent by weight
It has the effect of improving the service life in a wide area. However, if the amount exceeds 1%, the hardness becomes too high, the amount of sludge on the alloy surface increases, and other disadvantages such as self-discharge increase occur. The substantial range from 10 ^-2 to 10 ^0% is practical.

Further, since the composition and structure of the base sheet basically has the above-mentioned strength, the present invention also has the same cut edge even when it has a configuration in which another alloy layer is integrated on one side or both sides of the sheet. Have an effect.

On the other hand, the corrosion of the joint between the current collector (ear) of the negative electrode plate and the strap portion will be described. Generally, this kind of antimony-free alloy is adopted for the purpose of maintenance-free property and is often not replenished with water.
In particular, a battery called a hybrid for a bath uses an antimony grid for the positive electrode and a non-antimony grid for the negative electrode. In this battery, the antimony of the positive electrode is dissolved and deposited on the negative electrode, resulting in a large liquid loss. Then the strap part is exposed,
Further, when the base of the ear is exposed, the exposed portion is converted to lead sulfate with the help of wet sulfuric acid and oxygen, and the local pH rise causes rapid corrosion, leading to disconnection. Unfortunately, the disconnection of the exposed part causes sparks and explosions. Selenium stops the promotion of this corrosion. Non-antimony-based alloys generally have large crystal grain boundaries, and once part of the surface begins to corrode, corrosion progresses inwardly in a wedge shape. This is suppressed by the presence of selenium and prevents disconnection. This effect is sufficient if the amount of selenium is 0.002%. In the unlikely event that selenium is absent, calcium alloys commonly used in negative electrodes can be destroyed with a probability of 50% regardless of the presence of tin.

As described above, according to the present invention, when the non-antimony sheet-like alloy sheet is processed into a reticulated body to be used for the lattice, by incorporating calcium, tin, selenium and bismuth in lead, the high temperature life and the corrosion of the ears are improved. Control disconnection.

Examples The effects of the present invention will be illustrated by the following examples.

FIG. 1 shows an example of high temperature life characteristics of a lead storage battery to which the present invention is applied.

First, a lead-calcium-tin alloy was selected as a representative of non-antimony alloys for the base alloy. In this case, the weight% of calcium is 0.05 to 0.09%, tin is 0.2 to 0.3%, and the balance is lead, and selenium is widely selected from 10 ^-3 to 2 × 10 ⁰ %. The alloy sheet was obtained by melting the alloy to obtain a slab body of about 10 mmt, cold rolling this to 1 mmt, expanding it according to a conventional method, applying a paste, and drying to obtain an electrode plate. According to the US SAE test conditions at 75 ℃, discharge this at 25A for 4 minutes, charge at 14.8V for 10 minutes, repeat about 500 times, then 300 times.
At 30 seconds at A, the cycle until the voltage fell below 7.2V was obtained.
The life at that time was taken as A and shown as a relative value compared to the life S without addition. Bismuth 0.00 as a base
The case where 5% was further added is shown as B.

From these results, the effect of improving the high temperature life of selenium according to the present invention was recognized in a high range. Further, the effect was further recognized by the coexistence of bismuth. In these cases, the active material peels off the lattice without the standard selenium additive, whereas in A and B in the same cycle, there is little deformation or peeling, so resistance to elongation deformation and peeling of the oxide layer from the lattice are large. It shows that the corrosion resistance and the corrosion resistance are comprehensively improved.

Further, as a corrosion test on the negative electrode side, the electrolytic solution was lowered to about the top surface of the separator at 75 ° C. and allowed to stand. The failure rate of ear corrosion after 6 months in each 20 cells (120 cells) at that time
As shown in the figure. As is clear from this result, when the corrosion condition is adjusted, the failure rate becomes as high as 50% in the grid made of the lead alloy sheet containing no selenium. In the present invention, this is only 1 to 2 × 10
It can be suppressed even by the addition of selenium having a ^-3 % content.

EFFECTS OF THE INVENTION As described above, the present invention uses calcium as an alloy used for a lattice as a reticulated body by machining from a cold-rolled sheet-shaped alloy,
By using a lead alloy containing tin, selenium and bismuth, it is possible to not only improve the high temperature life, which was a weak point of batteries using this type of grid, but also suppress the special negative electrode ear corrosion that progresses under exposure conditions. However, its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a relative ratio of high temperature life and an amount of selenium added in an example of the present invention, and FIG. 2 is a diagram showing a relationship between a failure rate and an amount of selenium added. A: selenium-added non-antimony alloy of the present invention, B ... selenium and bismuth-added non-antimony alloy of the present invention.

Claims (1)

[Claims] 1. A lead storage battery using a lead alloy containing calcium, tin, selenium, and bismuth in a lattice formed from a cold-rolled antimony-free lead alloy sheet.