JPH06119936A - Sealed type lead-acid battery - Google Patents

Abstract

PURPOSE:To facilitate manufacture and improve the initial performance and lifetime characteristic by providing a separator in which silica particles as granulated powder are bound using a binder which is polytetrafluoroethylene. CONSTITUTION:Using polytetrafluoroethylene as a binder, granulated particles from silica powder are bound to fabricate a separator 3. This is combined with a negative electrode plate 2 and positive electrode plate 1 made from a stibium-free lead alloy lattice, and a group of electrode plates is fabricated. The plate group is inserted in a battery jar 4, and the voids around the plate group are filled with silica powder of the same sort used in fabricating the separator 3. Over the powder layer 6 a block 7 of phenol foams are stopped, and the layer 6 is fixed. After a lid 5 is welded to the battery jar 4, a certain quantity of sulfuric acid electrolyte is poured in from a liquid port, and after mounting an exhaust valve 8, charging is conducted to complete the intended battery. The silica powder should preferably be such as consisting of coarse secondary particles of 50-400mum generated through coagulation of silica fine powder having diameters from 10 to 40nm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved sealed lead acid battery.

[0002]

2. Description of the Related Art There are two types of sealed lead-acid batteries, a retainer type and a gel type, which utilize a so-called oxygen cycle in which an oxygen gas generated during charging of the battery is absorbed by a negative electrode. Lite
The na type is a mat-shaped separator (glass separator) made of fine glass fibers inserted between the positive electrode plate and the negative electrode plate.
It maintains the sulfuric acid electrolyte necessary for charging and discharging the battery and isolates both electrodes.
Taking advantage of such features, in recent years, starting with portable power supplies, cordless devices, backup power supplies for computers,
It has also come to be used for large stationary batteries and for starting the engine of automobiles.

However, the glass separator is a mat-shaped product made of extra fine glass fibers having a diameter of about 1 micron manufactured by a special method, and is more than a commonly used separator for lead-acid batteries. It is quite expensive, and it is difficult to insert the electrode group into the battery case because it is necessary to squeeze the electrode group strongly into the battery case to obtain the target battery performance. However, there is a drawback in that the manufacturing cost of the battery inevitably becomes high.

Further, the retainer-type sealed lead-acid battery has a small amount of sulfuric acid electrolyte that can be held in the glass separator, and has a battery capacity, especially a low value, as compared with a general open-type lead-acid battery that is rich in electrolyte. There was a drawback that the rate discharge capacity was inferior. Therefore, if you try to improve the discharge capacity by holding as much electrolyte as possible in the glass separator by using a glass separator with a wide gap between electrodes and a large thickness, the internal resistance of the battery will increase and the voltage during discharge will increase. When the characteristics of the glass separator are deteriorated, conversely, when a thin glass separator is used to improve the voltage characteristics, it becomes impossible to secure the electrolytic solution necessary for discharging, and the glass separator has a large porosity and a large pore size. There is a problem that a short circuit is likely to occur and the life is short.

On the other hand, the gel type is a sealed lead-acid battery in which a sulfuric acid electrolytic solution is gelled with colloidal silica or water glass, but sulfuric acid separates and leaks, or the mobility of sulfate ions in the gel. Battery performance is poor due to poor performance, and because the gel electrolyte does not have a gas passage for oxygen gas generated at the positive electrode to reach the negative electrode, the battery is repeatedly charged and discharged to cause water decomposition to form gel. There was a defect that the oxygen absorption reaction in the negative electrode did not occur until cracks occurred.

Therefore, in order to eliminate the above-mentioned drawbacks of the conventional sealed lead-acid battery, a granular type silica powder obtained by aggregating fine silica powder to form an electrolytic solution holder is not a retainer type but a gel type. Nonetheless, a sealed lead-acid battery has been proposed. This is a new structure in which coarse secondary particle powder (hereinafter referred to as silica powder) formed by agglomeration of fine primary particles of hydrous silicon dioxide is filled between the positive and negative electrode plates and around the electrode plate group. In such a sealed lead-acid battery, it is possible to impregnate and retain a sufficient amount of electrolytic solution in the powder without the discharge capacity of the battery being limited by the amount of electrolytic solution, and to fill the powder layer surrounding the electrode plate. In order to prevent deformation of the active material due to discharge,
It has become possible to significantly improve the initial performance and life performance of a sealed lead acid battery.

[0007]

However, the above-mentioned novel sealed lead-acid battery also has various problems to be solved. That is, in order to obtain the expected battery performance with this new sealed lead-acid battery, silica powder must be densely packed between the positive and negative electrodes with a uniform thickness. For this purpose, for example, a separator having a constant thickness as described in JP-A-2-165570 is used,
Using a thin ribbed separator as described in Japanese Patent Application Laid-Open No. 4-51470, a battery assembled while keeping the gap between the positive and negative electrode plates constant is subjected to vibration while applying silica powder between the electrodes and between the electrodes. Although it is filled around the plate group, it was very difficult to form a powder layer having a constant thickness between very narrow electrode plates.

In the former example using a separator having a constant thickness, since the electrode plate itself is not always flat and has a bend or a warp, a wide space or a narrow space is generated depending on a place, and especially the space between the spaces is narrow. By the way, there was a risk of a short circuit. Therefore, in consideration of safety, it is necessary to increase the gap between the electrodes, and if the gap is increased, the internal resistance increases and it is not possible to make a battery having a good high rate discharge performance.

On the other hand, when the ribbed separator is used as in the latter example, the resistance of the powder layer is added to the resistance of the separator, so that there is a drawback that the voltage characteristics are deteriorated especially at a high rate discharge. In addition, if the silica powder is not sufficiently filled, there is a fatal defect that the expected battery performance cannot be obtained, and in any case, special equipment is required for manufacturing the electrode plate group. However, there is a big problem in battery production that it takes a long time to fill the powder between the narrow poles.

[0010]

According to the present invention, a rubber-elastic paste prepared by kneading a granular silica powder with an aqueous suspension of polytetrafluoroethylene (PTFE, fluororesin) is drawn into a sheet. By using a separator which can be easily produced by the above, the above-mentioned drawbacks of the novel sealed lead acid battery are solved.

[0011]

1 is a schematic view showing a sealed lead-acid battery according to the present invention, and FIG. 2 is a cross-sectional view of a main part thereof. Here, 1 is a positive electrode plate in which a positive electrode paste is filled in a casting grid made of an antimony-free lead alloy. As an antimony-free lead alloy, Ca 0.05 to 0.12 wt%, Sn 0.20 to 1.0 wt%
Common lead-calcium alloys including can be used.

Reference numeral 2 denotes a negative electrode plate, which is manufactured by filling a casting grid made of an antimoly free lead alloy with a normal negative electrode paste containing a shrink-proofing agent such as lignin or barium sulfate. The negative electrode lead alloy is Ca 0.05-0.12wt%, Sn 0.001-0.5w
A general lead calcium-based alloy containing 10% can be used. In this embodiment, cast grids are used for the positive electrode and the negative electrode, but any expanded grid or punched grid in which a lead alloy sheet is expanded can be used. The electrode plate filled with the storage battery paste is aged in a room at 30 to 50 ° C before use. In particular, aging of the positive electrode plate is an important step in battery performance.

Reference numeral 3 is a separator made of granular silica powder produced using polytetrafluoroethylene as a binder. The separator used here can be easily manufactured as follows. First, a granular silica powder having a specific surface area of 150 to ²⁰⁰ m ² / g in which fine primary particles having primary particles of 10 to 40 nm are aggregated to form coarse secondary particles of 50 to 400 μm is prepared. It is convenient to use water glass or methyl methacrylate as a binder for forming the secondary particles, because the particles can be made into strong granular particles and the particles do not collapse during the kneading described later.

100 g of this powder was placed in a kneader, 20 g of an aqueous suspension containing 60% by weight of polytetrafluoroethylene was then added and mixed with 300 g of water, and this was added to the silica powder in the kneader and thoroughly mixed. Knead. At the beginning of kneading, the contents in the kneading machine are relatively free-flowing and are not sticky, but eventually they exhibit rubber elasticity. When this happens, the contents are taken out and passed through a pair of rolls to a thickness of 1.
If it is processed into a sheet of 00 mm and dried at 40 to 50 ° C, a sheet having a relatively high strength and cushioning property can be obtained. This was cut into a predetermined size to prepare a separator 3.

In the sealed lead acid battery according to the present invention, since the silica powder is filled around the electrode plate group, the size of the separator may be the same as that of the electrode plate or may be slightly larger or smaller. The separator thus produced had a density of about 0.4 g / cm ³ and a porosity of 85%. The porosity can be controlled to some extent by the amount of water to be added, the degree of kneading, the degree of pressing when passing through the rolls, etc. As a result of the experiment, a separator having a porosity of 90% or more could be obtained.

The addition amount (solid content) of polytetrafluoroethylene added to the silica powder is 10.
Although it is 7% by weight, if it is too large, the water repellency becomes strong and the finish becomes hard and the liquid absorbency of the separator deteriorates. . However, it has been found that a surfactant may be used to improve the liquid absorbing property, and fine glass or short fibers such as synthetic fibers may be added to improve the mechanical strength. As a result of various studies, it seems that the addition amount of polytetrafluoroethylene is preferably about 5 to 20% by weight in terms of solid content.

An electrode plate group was manufactured by combining the separator thus manufactured with the positive electrode plate 1 and the negative electrode plate 2 manufactured by using the above-mentioned antimony-free lead alloy grid. No special device was required for manufacturing the electrode plate group, and the conventional assembly device could be used as it was.

Next, after the prepared electrode plate group was inserted into the battery case 4, silica powder having the same characteristics as those used for preparing the separator 3 was filled around the electrode plate group. It was extremely easy to insert the plate group into the battery case because it was not necessary to apply pressure to the plate group. Further, in the present invention, since it is only necessary to fill the periphery of the electrode plate with the silica powder, the time required for the powder filling is only about 1 minute, and the powder filling time can be greatly shortened.

In the battery in which the powder filling was completed, the powder layer 6 was fixed by filling the upper portion of the powder layer 6 with a block 7 of a phenol resin foam having open cells. Then, after the battery case lid 5 is welded to the battery case 4, a predetermined amount of sulfuric acid electrolytic solution is injected from the liquid port, the exhaust valve 8 is attached, and the battery is charged to a capacity of about 30 Ah.
12V battery was completed.

Next, the sealed lead-acid battery (5 hR
A capacity of about 30 Ah, 12 V was applied at 6 A (0.
2C) Discharge and 150A (5C) discharge at −15 ° C. for capacity test, and then life test (discharge: 20A × 1h, charge: 5A × 5h, temperature: 40 ° C.) according to JIS standard. It was Table 1 shows the test results.

For comparison, in addition to the battery according to the present invention, there is a battery in which silica powder is filled between the electrodes or around the electrode plate group, but a control battery and a conventional product in which the separator according to the present invention is not used. As a result, a retainer type sealed lead acid battery was tested at the same time.

[0022]

[Table 1]

The battery of the battery A is according to the present invention, B and C are the same as the product A of the present invention, a reference product assembled by using the negative electrode plate, and D is a retainer type conventional product assembled by using the same electrode plate. Is. Conventional product D uses a glass separator with a thickness of 1.25 mm and applies pressure to the electrode plates to make the electrode plate spacing 1.00.
mm. The reference product B is a separator having a thickness of 1.00 mm and the gap between the electrodes is kept constant, and C is a separator with ribs (a separator thickness of 0.25 mm and a rib height of 0.7 mm).
5 mm) is used. As described above, the battery performances of both batteries were compared by setting the distance between the positive and negative electrode plates to 1.00 mm.

The product A of the present invention has 0.2C and 5C discharge capacities of 33.2Ah and 9.8Ah, respectively, and the fifth-second voltage is 9.68V and the discharge capacity and the fifth-second voltage are the conventional retainer type sealed battery D. The initial performance was higher than that of the conventional product, and particularly, the life performance was more than double that of the conventional product. The reason why the product of the present invention has a particularly long life as compared with the conventional product is considered as follows from the disassembly result of the battery after the life test.

That is, the positive electrode plate of the conventional product was remarkably deformed and collapsed when the electrode plate was lifted, whereas the positive electrode plate of the present invention had a considerably badly corroded grid, Almost no deformation of the plate was observed. It is considered that this is because the powder filled around the electrode plate group strongly pressed the electrode plate and prevented its deformation.

On the other hand, in the battery B tested as the control product, the life performance was only 52 cycles although the initial performance was comparable to the product of the present invention. This was because the separator was not used, so an internal short circuit occurred in the narrow space between the electrodes. Similarly, since the control product C also used a separator, the internal resistance of the battery was high and the voltage at the 5th second of high rate discharge was low. Further, it is difficult to densely fill the powder into the narrow gap of 0.75 mm, and therefore the life performance is also lower than that of the conventional product. Although the thickness of the sheet made of silica powder and polytetrafluoroethylene is 1.00 mm in the present embodiment, it is possible to make the sheet thinner, and the pore diameter is considerably smaller than that of the glass separator, and the thickness is small. Even so, there is no short circuit between the electrode plates to shorten the life.

[0027]

As described in detail above, according to the present invention, a novel sealed lead-acid battery using silica powder as an electrolyte solution holder by using a separator using polytetrafluoroethylene as a binder is used. Is easier to manufacture, and in addition, initial and life performance can be significantly improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram of the sealed lead-acid battery of the present invention.

FIG. 2 is a sectional view of a main part of the sealed lead-acid battery of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode plate 2 Negative electrode plate 3 Separator 4 Battery case 5 Battery container lid 6 Powder layer 7 Foam 8 Exhaust valve

Claims (2)

[Claims] 1. A powder layer in which silica powder is densely packed is formed around an electrode plate group assembled by using a porous separator formed by binding granular silica powder particles using polytetrafluoroethylene as a binder. The lead-containing structure is characterized in that the powder layer filled around the positive and negative electrode plates, the separator and the electrode plate is impregnated with a sulfuric acid electrolytic solution required for charging and discharging the battery. Storage battery. 2. A granular silica powder having a diameter of 10 to 4
0 nm (nanometer) silica fine powder aggregated 50
The sealed lead-acid battery according to claim 1, wherein silica powder composed of coarse secondary particles having a size of 400 μm (micron) is used.