JPH04337256A - Sealed lead-acid battery - Google Patents

Abstract

PURPOSE:To manufacture a sealed lead-acid battery at a low cost by using a positive electrode lattice made of a lead-antimony alloy, filling and arranging the silica fine powder between a positive electrode plate and a negative electrode plate, and impregnating and holding a sulfuric acid electrolyte in the fine powder and the positive and negative electrode plates. CONSTITUTION:When a lead-antimony alloy is used for a positive electrode lattice, antimony makes a corrosion layer generated on the interface between the positive electrode lattice and an active material porous, and the binding among grains is made firm. The early reduction of the capacity and the dropping of the active material can be prevented, and the short circuit caused by the extension of the lattice can be reduced. The eutectic section of the positive electrode lattice is eliminated, thus the antimony elution quantity from the positive electrode lattice can be reduced, the silica fine powder arranged between the positive electrode plate and the negative electrode plate absorbs antimony, and the movement of antimony from the positive electrode to the negative electrode is blocked. The silica fine powder is an inexpensive industrial material and has an excellent holding capability of sulfuric acid, thus a sealed lead-acid battery can be manufactured at a low cost.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in sealed lead-acid batteries.

0002

BACKGROUND OF THE INVENTION At present, there are two types of sealed lead-acid batteries in which the negative electrode absorbs oxygen gas generated during charging of the battery: a retainer type and a gel type. The retainer type inserts a matte separator (glass separator) made of fine glass fiber between the positive and negative electrode plates, which holds the sulfuric acid electrolyte necessary for discharge and isolates the two electrodes. In recent years, it has become widely used as a backup power source for portable equipment and computers, taking advantage of its characteristics such as no maintenance, no leakage, and no positioning.

However, on the other hand, there are many factors that increase the manufacturing cost of the battery, such as the high cost of the glass separator and the need to press the electrode plate group strongly and increase the strength of the battery case. They have drawbacks such as inferior low rate discharge performance compared to certain batteries (hereinafter referred to as liquid batteries), which is an obstacle to the widespread use of this type of sealed battery.

On the other hand, although the gel type is cheaper than the retainer type, it has the disadvantage that its battery performance is inferior to the liquid type and retainer type. In addition, most of both retainers and gel-type sealed lead-acid batteries use a lead alloy that does not contain antimony for the lattice. When a lead-antimony alloy is used in these batteries, antimony is eluted from the positive electrode grid during charging and discharging and deposits on the negative electrode plate, reducing the hydrogen overvoltage and increasing the amount of hydrogen generated by water splitting. As a result, a fatal dry-up occurs in sealed lead-acid batteries, resulting in the end of their lifespan.

[0005] For these reasons, in caged and gel type sealed lead-acid batteries, for example, a lead-calcium alloy is used as an antimony-free alloy. However, when lead-calcium alloys are subjected to charge-discharge cycles that include deep discharge, lead sulfate, a dense nonconductor, is formed at the lattice-active material interface during discharge, resulting in early capacity loss and active material This has the disadvantage that the bond between the lead dioxide particles weakens and the active material easily falls off. Furthermore, since lead-calcium alloys are much softer than lead-antimony alloys, they also have the disadvantage of being more susceptible to short circuits due to lattice elongation.

On the other hand, in the case of lead-antimony alloys, antimony makes the corrosion layer formed at the lattice-active material interface porous, and also strengthens the bonding force between lead dioxide particles, leading to early capacity loss and active material There is no falling off, and short circuits due to grid stretching are also less likely to occur. For these reasons, the biggest challenge for current sealed lead-acid batteries is to reduce costs and improve battery life performance at the same time.

[0007]

[Means for Solving the Problems] We believe that in order to eliminate the above-mentioned drawbacks of the conventional sealed lead-acid batteries, it is best to make it possible to use a lead-antimony alloy for the positive electrode grid. However, for this purpose, there are major problems in preventing antimony elution from the positive electrode lattice and preventing antimony from moving from the positive electrode to the negative electrode. The present invention solves these two problems.

First, in order to prevent the elution of antimony from the positive electrode grid, the metal structure of the low-antimony lead alloy is adjusted to suppress the elution of antimony during grid corrosion as much as possible. As is well known, in the structure of a lead-antimony alloy, a eutectic of lead and antimony (α+β layer) exists surrounding a lead solid solution layer (α layer) developed in a dendritic shape. When such a lead alloy undergoes anodization and corrodes, the eutectic portion is eroded from the alloy surface and corrodes. Since the eutectic portion has an extremely high antimony content, when this portion is corroded, a large amount of antimony is eluted into the electrolyte. The first point of the present invention is that the structure of a typical lead-antimony alloy is reorganized by heat treatment or the like to eliminate high antimony-containing portions such as eutectic portions.

Another point is that fine silica powder is used in sealed lead-acid batteries by taking advantage of the fact that fine silica powder adsorbs antimony. In other words, a positive electrode grid made of a lead-antimony alloy is used, silica fine powder is filled and arranged at least in the gap between the positive electrode plate and the negative electrode plate, and the amount of sulfuric acid electrolyte required for charging and discharging is applied to the fine powder and the positive and negative electrode plates. It is characterized by being impregnated with and retained.

[0010] By using a lead-antimony alloy for the positive electrode lattice, antimony makes the corrosion layer formed at the positive electrode lattice-active material interface porous and strengthens the bond between particles.
It is possible to prevent early capacity reduction and active material falling off, and it is also possible to reduce short circuits due to lattice elongation. By eliminating the eutectic part of the positive electrode lattice, the amount of antimony eluted from the positive electrode lattice can be significantly reduced, and the silica fine powder placed in the gap between the positive electrode plate and the negative electrode plate adsorbs antimony and prevents antimony from flowing from the positive electrode to the negative electrode. Prevent the movement of antimony. the result,
Since the drop in hydrogen overvoltage due to antimony is extremely small, water splitting hardly increases, and the most important feature of sealed lead-acid batteries, which is no maintenance and no water replenishment, is not impaired. Furthermore, fine silica powder is a very inexpensive industrial material and has an excellent ability to retain sulfuric acid, making it possible to manufacture sealed lead-acid batteries at low cost in place of retainer and gel types.

[0011]

EXAMPLES The present invention will be explained below based on examples. First, the influence of the alloy structure of the lead-antimony alloy on the amount of antimony elution was investigated. Antimony content 0.5
After casting a lead alloy plate adjusted to ~4.0% by weight, approximately 240%
The mixture was kept at 0.degree. C. for 1 hour and then rapidly cooled. The dimensions of the lead alloy plate were 10 cm x 10 cm and a thickness of 1 mm. Two of these lead alloy plates A were placed in sulfuric acid and an antimony elution test was conducted.

[0012] For comparison, a similar test was also conducted on lead alloy plate B which had not been heat treated. The specific gravity of sulfuric acid is 1
．． 30. The temperature was 50° C., and a current of 1 A was applied for one week. Figure 1 shows the amount of antimony eluted after the test.

The amount of antimony eluted from the heat-treated lead alloy sheet A was significantly reduced compared to the non-heat-treated sheet B. The decrease in elution amount increased as the amount of antimony in the alloy increased. The reason for this is thought to be as follows. Through heat treatment, the metal structure of the lead alloy exhibits a unique structure in which the β layer is dissolved into the α layer, rather than the dendrite structure as in conventional metal structures. As the amount of antimony in the alloy increases, the number of eutectic parts increases, so the effect when the number of eutectic parts decreases increases. As mentioned earlier, the solid solution phase is far more resistant to corrosion than the β phase with a eutectic composition, and is thought to have prevented the elution of antimony.

Next, as fine silica powder, the primary particles are 10
The porosity and liquid retention amount were investigated using a material with a diameter of ~40 millimicrons and a surface area of approximately 120 m2/g. First, in order to understand the characteristics of the silica fine powder, we investigated the amount of liquid it can hold and compared it with a glass separator made of glass fiber with a diameter of about 1 μm that is used in current cage-type sealed lead-acid batteries. The amount of liquid retained is the amount of liquid that can be held by the silica fine powder or the glass separator, and was determined through experiments. First, dilute sulfuric acid with a specific gravity of 1.30 (20° C.) was filtered through fine silica powder or a glass separator placed on a glass filter, and the amount of liquid retained therein was defined as the amount of retained liquid. The results are shown in Table 1.

[0015]

[Table 1]

Although the liquid holding capacity of silica fine powder is slightly inferior to that of glass separators, it has an excellent liquid holding capacity of 0.87cc/cm3, so a new type of sealed lead-acid battery is used to replace the retainer and gel type. It turns out that it can be made.

The antimony adsorption power of the above-mentioned silica fine powder was also investigated. For comparison, β-PbO2 and
TiO2 (rutile type) was also tested at the same time. In the test, fine silica powder, β-PbO2, and TiO2 (rutile type) were placed in dilute sulfuric acid with a specific gravity of 1.30 containing antimony.
After stirring for a certain period of time, the amount of antimony reduced in dilute sulfuric acid was determined and used as the amount of adsorption. The results are shown in Figure 2. FIG. 2 shows the relationship between the antimony concentration in dilute sulfuric acid and the amount of antimony adsorbed.

Generally, metal oxides having a tetragonal crystal structure, such as β-PbO2 and TiO2 (rutile type), are known to adsorb antimony in a solution. However, for use in lead-acid batteries, it must be resistant to sulfuric acid;
It must meet other conditions such as having high antimony adsorption power, being inexpensive, and not causing any harm to the battery.

β-PbO2 is used as a positive electrode active material, but as shown in FIG. 2, it has a small antimony adsorption power, so it cannot sufficiently prevent the movement of antimony from the positive electrode plate to the negative electrode plate in a lead-acid battery.

TiO2 (rutile type) has almost the same antimony adsorption power as fine silica powder, but it is expensive, so adding it to the battery in an amount sufficient to prevent antimony migration will result in a significant increase in cost. .

On the other hand, fine silica powder satisfies all of the above conditions because it has excellent antimony adsorption power, is inexpensive, and is harmless to batteries. When fine silica powder is used as an electrolyte holder and a lead-antimony alloy is used for the positive electrode grid, the fine silica powder adsorbs antimony that moves from the positive electrode to the negative electrode, creating a battery with almost no adverse effects caused by antimony as described above. It is possible to create one.

Next, a battery was actually produced and tested.

[0023]

[Table 2]

For comparison purposes, as shown in Table 2, tests were also conducted on batteries using lead-antimony alloys and lead-calcium alloys that were not heat-treated as positive electrode grid alloys, and glass separators as electrolyte holders. I did it. The amount of antimony in the lead-antimony alloy was 2.5% by weight, and the heat treatment conditions were the same as in the case of the lead alloy plate described above. Note that a lead-calcium alloy was used for the negative electrode grid. Standard positive and negative electrode active materials were used, and dilute sulfuric acid with a specific gravity of 1.30 was used as the electrolyte, and approximately 2.8
A sealed lead acid battery for automobiles with a capacity of Ah was assembled.

[0025] Using these batteries, JISD-5301
We conducted a lifespan test to examine changes in discharge capacity and amount of liquid loss. The discharge capacity is compared with the capacity before the test as 100%, and the amount of liquid reduction is expressed in weight % with the capacity before the test as 0%. The results are shown in Figure 3.

[0026]No. Battery No. 3 had the shortest lifespan and a large amount of fluid loss. This is because antimony eluted from the positive electrode grid is deposited on the negative electrode plate, increasing water decomposition and reducing the amount of electrolyte. No. Although the amount of fluid loss was small for batteries No. 4 and 5, No. The lifespan was shorter than that of battery No. 1. This is because the positive electrode active material deteriorates easily because it does not contain antimony, and because lead-calcium alloys are softer than lead-antimony alloys, the lattice stretches and short circuits occur. It is the cause. No. The battery No. 2 is No. The lifespan is considerably better than batteries No. 3, 4, and 5, but No. Compared to the battery No. 1, the capacity decreases and the amount of liquid decreases more. This is because although the silica fine powder adsorbed antimony to some extent, some of it was precipitated on the plate.

In contrast, No. 1, which is a product of the present invention. 1
A battery using a heat-treated lead-antimony alloy for the positive electrode lattice and a fine silica powder for the electrolyte holder had the longest life cycle and had the least amount of liquid loss. This is because a lead-antimony alloy is used for the positive electrode lattice, which causes less deterioration of the positive electrode active material and less elongation of the lattice.
The reasons for this are that the heat treatment eliminated the eutectic part and the amount of antimony eluted decreased, and that the silica fine powder prevented antimony from moving from the positive electrode to the negative electrode, resulting in a decreased amount of liquid loss.

[0028] This time, the number of primary particles as fine silica powder was 10
Although silica fine powder having a surface area of 40 millimicrons and a surface area of approximately 120 m2/g was used, the same effect can be obtained with any silica fine powder having a surface area of 20 m2/g or more. In addition, the same effect as in this example can be obtained for a clad sealed lead-acid battery using a lead-antimony alloy without the eutectic part in the positive electrode lattice and using the above-mentioned silica fine powder in the electrolyte holder.
In other words, it can be expected to have a long life with less liquid loss.

[0029]

Effects of the Invention As is clear from the above embodiments, the sealed lead-acid battery according to the present invention uses a positive electrode lattice of a lead-antimony alloy without a eutectic part, and has at least a positive electrode plate and a negative electrode plate. The disadvantages of conventional sealed lead-acid batteries can be overcome by filling and disposing fine silica powder in the gap and impregnating and holding the fine powder and positive and negative electrode plates with the amount of sulfuric acid electrolyte required for charging and discharging. , its industrial value is enormous.

[Brief explanation of the drawing]

[Figure 1] Diagram comparing the relationship between the amount of antimony in the alloy and the amount of antimony eluted

[Figure 2] Diagram showing the relationship between the amount of antimony adsorbed by fine silica powder, TiO2, and β-PbO2 and the antimony concentration in dilute sulfuric acid.

[Figure 3] Diagram showing volume change and liquid loss amount during cycle life test

Claims (1)

[Claims] 1. A sealed lead-acid battery in which oxygen gas generated during charging of the battery is absorbed by a negative electrode, the battery having a positive electrode grid made of a lead-antimony alloy, wherein the positive electrode grid is made of an alloy. The structure has substantially no eutectic part, and fine silica powder is filled and arranged in the gap between the positive electrode plate and the negative electrode plate, and the amount of sulfuric acid electrolyte required for charging and discharging is applied to the fine powder and the positive and negative electrode plates. A sealed lead-acid battery characterized by being impregnated and retained.