JPH03149754A - Manufacture of sealed lead-acid battery - Google Patents

Abstract

PURPOSE:To make a lead-acid battery lightweight and obtain high performance by immersing an expand-machined copper lattice in a molten metal with the melting point higher than that of lead to form the first film layer, and immersing it into molten lead or lead alloy to form the second film layer. CONSTITUTION:An expand-machined copper lattice is immersed in molten metal with the melting point higher than that of lead, e.g. zinc or aluminum, to form the first film layer 4, then it is immersed in the molten lead or lead alloy to form the second film layer 5. When the copper lattice is immersed in the molten metal with the melting point higher than that of lead, a lattice frame 1 is formed into a roundish cross section shape with no edge section as a whole, thus uniform film layers 4 and 5 are formed by immersing it in molten lead. The elution of copper is prevented by simple fusion plating, a lead-acid battery is made lightweight, and its performance is improved.

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 gas generated during battery charging: a retainer type and a gel type.Currently, the retainer type is most commonly used. .

Retainer-type sealed lead-acid batteries have a mat-like separator (glass separator) made of fine glass fiber inserted between the positive and negative electrode plates, which holds the sulfuric acid electrolyte necessary for discharge, and 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 the demand for it as a power source for portable equipment and communication equipment is rapidly increasing, and in the future it will be used for starting cars. It is expected that its uses 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, since the lattice body, which has a major influence on the performance of lead-acid batteries, is made of lead, which has the highest density among metals and also has a fairly high electrical resistance, as long as a lead alloy lattice body is used, it is not possible to expect much improvement in performance. .

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 #J 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 most suitable method is to coat the copper grid with lead or a lead alloy by electroplating. However, electroplating requires 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 dobuzuke), 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. . However, when we compared the battery performance of sealed lead-acid batteries using a lattice made of expanded rolled copper sheets with lead hot-dip plating and one with lead electrification applied, we found that The overdischarge characteristics of batteries using grids are poor, and copper melts; I
There were also many s31. So when we investigated the cause of this, we found that
It was 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 applied.

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 using FIG. 2. A and B show the cross sections of the grid when hot-dip plated and electroplated, respectively. Reference numeral 1 indicates a copper lattice beam, 2 a lead coating layer, and 3 a tip of a rectangular cross section of the lattice crosspiece. As is clear from the figure, in B with electroplating, lead coating Jl
12 was almost uniform in thickness, whereas in A, which was hot-dip plated, the lead coating layer was thick near the center of the rectangular cross section of the lattice crosspiece 1, and a lead coating layer was formed at the tip 3. It wasn't. The poor overdischarge performance of sealed lead-acid batteries using hot-dip 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. 63-174276, after forming a first coating layer by hot-dipping 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-dip immersion plating of lead instead of electroplating with 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.

SUMMARY OF THE INVENTION The present invention overcomes the above drawbacks by first immersing an expanded copper grid in a molten bath of a metal with a higher melting point than lead, such as zinc or aluminum, to form a first coating. The main idea is to form a second coating layer by immersing the copper in a molten bath of lead or lead alloy, thereby easily forming a uniform coating layer around the copper hem. was completed. Hereinafter, the present invention will be explained based on examples.

Example First, an expanded grid was prepared by rolling out a rolled copper sheet having a thickness of 0.2 mm. Next, I installed this copper grid,
After cleaning and degreasing, it was dried. Zinc chloride (Zn) was added to form a first coating layer of zinc on the dried copper grid.
Zinc (Zn) using an aqueous solution of Cl t ) as a flux
Hot-dip plating was performed. Zinc molten bath is 450-460
℃, the copper grid was briefly dipped and pulled up, and the molten zinc droplets were shaken off to form a coating layer of zinc. Observing the cross section of the lattice cross section at this point, the shape is similar to that shown in Figure 2A, with almost no zinc coating layer at the four corners (edges) of the lattice cross section, and the thickness of the coating layer at the center of the rectangular cross section. It was big. Therefore, the above-mentioned copper grid on which the first coating layer of zinc was formed was immersed again in an aqueous solution flux of zinc chloride, and then immersed in a molten bath of a 3% tin alloy with a lead layer at a temperature of about 350°C. A second Wi layer of the lead alloy was formed. The temperature of the lead alloy bath is the melting point of zinc (420°C), which is the first coating layer.
Since the temperature was lower, a uniform second coating layer of lead alloy was formed without zinc dissolving.

FIG. 1 shows a cross section of an expanded copper grid subjected to the above treatment, in which numeral 4 indicates a first coating layer of zinc, and numeral 5 indicates a second coating layer of lead alloy. Aluminum instead of zinc (melting point 660℃
), a uniform coating layer of lead alloy as shown in FIG. 1 was obtained.

The formation of a uniform lead alloy coating layer was made possible by using a molten bath of a metal layer with a higher melting point than lead (which has a melting point of 321°C) (of course, it must be lower than the melting point of copper, 1083°C). By immersing the copper grid, the cross-section of the grid cross section was rounded throughout with no edges, and a uniform coating layer was formed by immersing it in the lead alloy bath. be.

Next, in order to demonstrate the effects of the present invention, a sealed lead-acid 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. Test results are not shown in Table 1.

Table 1 1 Treatment of battery 1 negative electrode grid 1shR capacity SAE life III 1st layer 1 second layer 1 hour-minute 1 (~) [A Zinc Lead alloy 4-35 40000 Aluminum Lead alloy 4-38 40000 Lead alloy none
4-30 500 over discharge test
Connect a 0W lamp and leave it for a month, then turn on the 2.5W lamp.
A 5 hR capacity test was performed after charging at a constant voltage of V/cell. After that, the life test specified in S^[ was conducted. From the test results in Table 1, test batteries A and B according to the present invention had almost no difference in 5hR capacity after constant voltage charging from conventional product C, but in the SAE life test conducted after the capacity test,
Inventive products A and B showed good life performance of 4,000 or more, while conventional product C, in which the copper grid was only hot-dipped with a lead alloy, had a life of only 500 or more. The conventional product had a large amount of liquid loss, and the current at the end of charging during the life test was large, so it seems that copper was eluted. Invention Crystals A and B4 There was no such problem, and the effect of applying M-dip plating to the first and second layers of the copper lattice was remarkable.

Effects of the Invention As described above, according to the present invention, the elution of copper can be prevented by simple hot-dip plating, and the present invention has shown remarkable effects in reducing the weight and improving the performance of lead-acid batteries. Although zinc or aluminum was used as the first coating layer in this example, the same effect can be obtained with any metal or alloy that has a melting point lower than these alloys or copper and higher than lead. Needless to say, Vl.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a copper grate machine according to the present invention;
The figure is a cross-sectional view of a conventional copper grid machine with molten lead foil and electric wire. 1...Copper lattice machine, 2.5...Lead coating layer, 4...Zinc coating layer l

Claims (1)

[Claims] 1. A lattice formed by expanding a thin plate of copper or a copper alloy is immersed in a molten bath of a metal whose melting point is higher than that of lead to form a first coating layer of the metal on the surface of the copper, and then a first coating layer of the metal is formed on the surface of the copper. A method for manufacturing a sealed lead-acid battery, comprising: forming a second coating layer on the first coating layer by immersing the plate in a molten bath of the invention, and then filling the negative electrode plate with a negative electrode paste.