JPH03152872A - Manufacture of sealed lead-acid storage battery - Google Patents

Abstract

PURPOSE:To make a sealed lead-acid battery lightweight and improve the performance thereof by applying the constitution wherein copper or a copper alloy sheet is dipped in the melt bath of metal having a higher melting point than copper and not causing a drop in a hydrogen overvoltage for forming the first film layer on the surface thereof, subjected to an expansion process and then further dipped in the melt bath of lead or lead alloy for forming the second film layer on the first film layer. CONSTITUTION:For forming the first film layer of metal having a higher boiling point than lead and not causing a remarkable drop in hydrogen overvoltage, for example, a Pb-3% Ca alloy, on copper grill, the aforesaid alloy is applied by means of a hot dipping process. The melt bath of the aforesaid alloy is kept at 450 to 460 deg.C and a copper sheet is dipped therein for a short time and pulled up for the formation of a film layer thereon. Then, the sheet is subjected to an expansion process and formed into a grill shape. Then, the aforesaid copper grill is dipped in a water solution of zinc chloride and then dipped in the melt bath of Pb-3% Sn alloy having a temperature of about 350 deg.C, thereby forming the second film layer on the first film layer. The temperature of the Pb-3% Sn alloy bath is lower than about 400 deg.C pertaining to the Pb-0.3% Ca alloy as the first film layer. Consequently, the second film layer is formed without causing the melting of the first film layer.

Description

[Detailed description of the invention] Industrial applications The present invention relates to improvements in sealed lead-acid batteries.

Conventional technology and its challenges There are two types of sealed lead-acid batteries that allow the negative electrode plate to absorb oxygen scum generated during battery charging: a retainer type and a gel type.Currently, the retainer type is the most commonly used type. .

A cage-type sealed lead-acid battery has a mat-like separator (glass separator) made of fine glass fibers inserted between the positive and negative electrode plates, which holds the sulfuric acid electrolyte necessary for discharge and separates both electrode plates. Isolation is in place.

This sealed lead-acid battery has excellent features such as no maintenance, no leakage, and no positioning, and is also highly reliable, so it is rapidly gaining demand as a power source for portable equipment and communication equipment, and will be used in automobiles in the future. It is expected that applications such as starting applications will further expand. Along with this, demands for higher performance, smaller size and lighter weight are increasing, and new technologies different from conventional ones are required.

In order to make lead-acid batteries lightweight and high-performance, it is necessary to reduce the lead parts used in the battery and the internal resistance of the battery as much as possible. Certain results have been achieved. However, it does not have a large effect on the performance of lead-acid batteries, and since the lattice body is made of a material that has the highest density among metals and has a fairly high electrical resistance, as long as a lead alloy lattice body is used, there will be little improvement in performance. I can't hope.

Therefore, it has been proposed to use a metal that is lighter than lead and has lower electrical resistance, such as copper, as the current collector.

However, the problem here is copper elution. Since copper has a lower hydrogen overvoltage than lead, when eluted copper is deposited on the negative electrode plate, self-discharge is promoted and the amount of hydrogen gas generated increases.

Therefore, in order to prevent the elution of copper, a method has conventionally been used in which the copper grid is completely coated with lead or a lead alloy. The method most suitable for this purpose is to coat the copper grid with lead or a lead alloy by electroplating. However, electroplating takes a considerable amount of time and is expensive, so it is not suitable for mass production such as lead-acid batteries for automobiles.

Therefore, instead of electroplating, the so-called hot-dip plating method (commonly called gutter plating), in which the copper grid is immersed in a molten bath of lead or lead alloy, is convenient because a coating layer can be formed in an extremely short time. 6 However, when we built a sealed lead-acid battery using a lattice made from expanded rolled copper sheets and applied lead fusion plating to one and one to which lead electrification lattice was applied, and compared the battery performance, we found that The overdischarge characteristics of batteries using copper grids were poor, and the amount of copper eluted was large. When we investigated the cause of this, we found that the shape of the lead coating layer was significantly different between the two, and that the lead coating layer was non-uniform when hot-dip plating was used.

The results of microscopic observation of the cross section of a copper expanded grid on which a lead coating layer has been formed are explained with reference to FIG. 3. A and B show the cross sections of the grid cross section when melt-plated and electroplated, respectively. Reference numeral 1 indicates a copper lattice crosspiece, 4 a lead coating layer, and 5 a tip portion of a rectangular cross section of the lattice crosspiece. As is clear from the figure, in B, which was electroplated, the lead coating layer 2
The thickness was almost uniform, whereas in A, which was hot-plated, the lead coating layer was thick near the center of the rectangular cross section of the lattice crosspiece 1, and almost no lead layer was formed at the tip 5. The poor overdischarge performance of sealed lead-acid batteries using melt-plated copper grids was due to the non-uniformity of the lead coating layer described above.

Therefore, as a means to solve the above-mentioned drawbacks, for example, according to Japanese Patent Application Laid-open No. 174276/1983, after forming a first coating layer by hot-dip plating a lead alloy on a copper expanded grid, A method has been proposed in which a uniform second coating layer is formed by plating. However, this method requires time-consuming and costly electroplating as described above, and is therefore unsuitable for mass-produced lead-acid batteries. Also, if you try to form the second coating layer by hot-dipping lead plating instead of electroplating lead, the lead alloy in the first coating layer has a temperature below the melting point of lead, so if you immerse it in a molten lead bath, The lead alloy of the first coating layer melts out, making it impossible to form a uniform coating layer.

Means for Solving the Problems The present invention solves the above-mentioned drawbacks by immersing a metal in advance in a molten bath of a metal that has a higher melting point than lead and does not significantly reduce the hydrogen overvoltage, such as a Yen-α alloy. The basic idea is to expand a copper or copper alloy sheet with a first coating layer formed on its surface, and then immerse it in a molten lead or lead alloy bath to form a second coating layer. This made it possible to easily form a uniform coating layer around the copper shim. Hereinafter, the present invention will be explained based on examples.

Example First, a rolled copper sheet having a thickness of 0.211 mm was washed with an organic solvent, degreased, and then dried. Pb-0 on the copper grid after drying
, 3% α alloy, the alloy was melt-plated using an aqueous solution of ammonium chloride as a flux. The molten bath of Pb-0,3%O alloy is 45
0 to 460°C, dipped the copper sheet for a short time and pulled it up,
Drops of molten alloy were shaken off to form a coating layer. Then, the sheet was expanded into a predetermined grid shape.

Observing the cross section of the lattice cross section at this point, as shown in Figure 1, copper mist is seen only on the cut surface of the copper lattice cross section 1 during the expanding process, and the rest is on the false-〇 alloy coating layer 2. It was evenly covered. Therefore, the above-mentioned copper grid on which the first coating layer of -α alloy was formed was immersed in an aqueous solution flux of zinc chloride, and then immersed in a molten bath of Pb-3% alloy at a temperature of 350°C to coat the first coating layer. A second coating layer of the lead alloy was formed over the layer. The temperature of the Pb-3%Sn alloy bath is the same as that of the first coating layer P.
Since the melting point of the b-0,3% alpha alloy is lower than the melting point (approximately 400 DEG C.), the second coating layer was formed without melting the first coating layer.

Figure 2 shows the cross section of the expanded copper grid subjected to the above treatment, 2 is the first coating layer of pb-Ca alloy, 3 is Pb
-8n alloy second coating layer.

The formation of a uniform lead alloy coating layer was made possible by immersing the lead-α alloy layer in a molten bath, which has a higher melting point than lead (melting point 327°C) and does not harm battery performance. By subjecting the copper sheaths 1 to 1 to A-spant processing, the edges of the lattice bars are made of lead alloy, so that even when a second coating layer is formed, the edges of the copper machine will not be exposed and will be replaced. This is because the edges of the first coating layer were exposed.

Next, in order to demonstrate the effects of the present invention, a sealed type 4 battery was prototyped using the above-mentioned grid, and an over-discharge storage test was conducted in which copper elution was the most problematic issue. The test results are shown in Table 1.

Table 1 Over-discharge storage test was conducted by connecting a 10W lamp to the test battery and leaving it for 1 month, then charging at a constant voltage of 2.5V/cell, and then conducting a 5hR capacity test. After that, a life test specified in S8F was conducted. From the test results in Table 1, the 5hR capacity after constant voltage charging of test battery A according to the present invention was almost the same as that of conventional product B;
In the AE life test, product A of the present invention showed a good lifespan of 4000~, while conventional product B, which was hot-plated with lead alloy only after expanding the copper sheet, had a lifespan of only 500~. It became. Conventional product B had a large amount of liquid loss and a large end-of-charge current during the life test, so it seems that copper was eluted.Product A of the present invention did not have this problem, and when using a copper sheet. The effect of melt plating after expanding was remarkable.

Effects of the Invention As described above, according to the present invention, copper elution can be prevented by simple hot-dip plating, and a remarkable effect has been shown in reducing the eaves weight and improving the performance of lead-acid batteries. In this example, a Pb-0.3%O alloy was used as the first coating layer, but any alloy that has a melting point lower than copper, higher than lead, and does not significantly reduce the hydrogen overvoltage may be used. Needless to say, this effect can be obtained.

[Brief Description of the Drawings] Figure 1 is a cross-sectional view of a copper grating immediately after expanding to show the progress of manufacturing a copper grating according to the present invention, and Figure 2 is a cross-sectional view of a copper grating machine based on the present invention. Figures 1 and 3 are diagrams, without showing the cross section, of a conventional copper lattice machine which has been subjected to molten lead plating and electroplating. 1... Copper lattice machine, 2... Pb-Ca alloy coating layer, 3
...Pb-8n alloy coating layer

Claims (1)

[Claims] 1. After immersing a thin plate of copper or copper alloy in a molten bath of a metal or alloy that has a higher melting point than lead and does not significantly reduce hydrogen overvoltage to form a first coating layer made of the metal on the surface of the copper. It is characterized by using a negative electrode plate that is expanded and then immersed in a molten bath of lead or lead alloy to form a second coating layer on the first coating layer, and then filled with negative electrode paste. A method for manufacturing a sealed lead-acid battery.