JPH06295720A - Lead-acid battery separator - Google Patents

Abstract

PURPOSE:To improve initial characteristics or service life performance of a battery by using a lead acid battery separator formed by binding silica powder and a small quantity of microporous polypropylene together while using polyfluoro polymer as a binder. CONSTITUTION:A lead-acid battery separator 3 formed by binding silica powder and a small quantity of acid resistant-oxidation resistant microporous resin powder together while using polyfluoropolymer as a binder, is used in a sealed lead-acid battery. Since this lead-acid battery separator 3 is formed by binding the powder constituting this together by the binder and is formed in an elastic sheet, productivity of a battery is improved, and since an interval between plates becomes also constant, the danger of a short circuit is eliminated. Since there exists only a powder layer between the plates, useless resistance is not caused, so that the battery having excellent initial and service life performance can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a lead storage battery separator.

[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 from extra fine glass fibers with 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. In addition, the retainer-type sealed lead acid battery has less sulfuric acid electrolyte that can be held in the glass separator, and the battery capacity, especially low rate discharge capacity, is greater than the open type lead acid battery that is rich in electrolyte. It had the drawback of being inferior.

Therefore, if an attempt is made to improve the discharge capacity by holding as much electrolytic solution as possible in the glass separator by using a glass separator having a large gap between electrodes and a large thickness, the internal resistance of the battery becomes large, and the discharge becomes large. When the thin glass separator is used to improve the voltage characteristics, it becomes impossible to secure the electrolyte necessary for discharging, and the glass separator has a large porosity and a large pore diameter. However, there is a problem that short-circuiting of the separator easily occurs 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 or a thin separator with ribs as described in JP-A-4-51470 is used. Then, the silica powder is filled between the electrodes and around the electrode plate group while applying vibration to the assembled battery so that the gap between the positive and negative electrode plates is kept constant. It was very difficult to form a thick powder layer.

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 particularly the space between the spaces is narrow. By the way, there was a risk of a short circuit. Therefore, considering the safety, the gap between the electrodes must be increased, and if the gap is increased, the internal resistance increases and it is not possible to make a battery having a high high-rate discharge performance. On the other hand, even when a 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 particularly at a high rate discharge.

Further, 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, a special device is required for manufacturing the electrode plate group. In addition, there is a big problem in battery manufacturing that it takes a long time to fill the powder between the narrow electrodes.

[0010]

The present invention has solved the above-mentioned drawbacks of the novel sealed lead-acid battery, and its gist is to use silica powder and a small amount of acid resistance and oxidation resistance with polyfluoropolymer as a binder. It is intended to use a lead-acid battery separator characterized by being combined with a microporous resin powder that it has.

[0011]

The separator for a lead-acid battery of the present invention uses the powder constituting the same as the electrolytic solution holder, but since the powder is in the form of a sheet having elasticity and being bound by a binder, the conventional sheet Batteries can be assembled in the same way as using a separator, which improves battery productivity.
Further, since the electrode plate spacing is also constant, there is no risk of short circuit. Furthermore, since there is only a powder layer between the electrode plates, useless resistance does not occur, and by using the separator of the present invention, a battery having excellent initial and life performances can be obtained.

[0012]

EXAMPLES A lead-acid battery separator according to the present invention was manufactured as follows.

First, a granular silica powder having a specific surface area of 180 to 250 m ² / g in which fine primary particles having a primary particle size of 10 to 40 nm are aggregated to form coarse secondary particles having a size of 50 to 400 μm was prepared. A commercially available product produced by spray drying silica sol was used as the granular silica powder.

Nine kinds of mixed powders shown in Table 1 were prepared by using the above-mentioned granular silica powder and microporous polypropylene as the microporous resin powder and changing the mixing ratio thereof. The microporous polypropylene used here had a mean particle size of 5 μm, and a commercially available product was crushed to adjust the particle size.

[0015]

[Table 1]

Next, 100 g of the mixed powder shown in Table 1 was put into a kneader, polytetrafluoroethylene (PTFE) was used as the polyfluoropolymer, and an aqueous suspension containing 60% by weight thereof was prepared in Table 1. The mixture was added to the mixed powder in the kneader at a ratio shown in Table 1 and kneaded sufficiently.

At the beginning of kneading, the contents in the kneading machine are relatively not sticky, but eventually they exhibit rubber elasticity. In such a state, the contents are taken out, passed through a pair of rolls, and formed into a sheet having a thickness of 1.00 mm.
When dried at ℃, a sheet having a relatively high strength and cushioning property was obtained. This was cut into a predetermined size to prepare a separator.

Table 1 shows the porosity and permeability of the separator thus produced. Here the permeability is 10 cm
The time (second) required for water to permeate the entire surface of the separator piece by placing the corner separator piece horizontally on the water surface is shown. The porosity was larger than that when the silica powder used as the raw material was densely packed.

When the amount of microporous polypropylene added to the silica powder was increased to 0 to 20%, the porosity was increased accordingly. However, when the amount added was 5% or more, the permeability decreased. Further, when the amount of PTFE added was decreased, the porosity was increased and the permeability was also improved.

On the other hand, the silica powder alone reduced the tensile strength when the amount of PTFE added was reduced, but the one with the addition of microporous polypropylene did not show any reduction in the tensile strength and was not broken during battery assembly. It was

Battery No. 1 was manufactured using the above-mentioned lead battery separator. 1-9 were assembled and the performance was investigated. Figure 1
[FIG. 2] is a sectional view of a main part of a sealed lead-acid battery using the lead-acid battery separator according to the present invention, in which (A) is a front view and (B) is a side view.

First, the positive electrode plate 1 and the negative electrode plate 2 and Table 1
An electrode plate group was produced by combining the separator 3 described. No special device was required for manufacturing the electrode plate group, and the conventional assembly device could be used as it was.

After the prepared electrode plate group was inserted into the battery case 4, silica powder 6 having the same characteristics as those used for preparing the separator 3 was filled around the electrode plate group. Inserting the electrode group into the battery case was extremely easy because it was not necessary to apply much pressure to the electrode group.

Further, according to the present invention, since it is only necessary to fill the periphery of the electrode plate group with the silica powder, the time required for filling the powder is only about 1 minute, and the conventional method of filling the powder between the electrodes is also used. Compared with the case, the powder filling time could be shortened significantly.

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 the phenol resin foam having open cells. Weld the battery case lid 5 to the battery case 4,
Inject a predetermined amount of sulfuric acid electrolyte from the liquid port, attach the exhaust valve 8,
Further, charging was performed to complete a 12V battery having a capacity of about 30 Ah.

When injecting the sulfuric acid electrolytic solution, the batteries 2 and 3 can be infused in substantially the same time as the conventional battery 1, and in the batteries 4 to 6 in which the compounding ratio of the microporous polypropylene is large, 1.
5 to 2.5 times longer than that of the conventional battery 1. As shown in Table 1, the lower the permeability of the separator, the longer the injection time. On the other hand, the batteries 7 to 9 using the separator having excellent permeability were able to inject the liquid in 0.3 to 0.8 times the time of the conventional battery.

As the positive electrode plate 1, a casting grid made of an antimony-free lead alloy filled with a positive electrode paste was used. As an antimony-free lead alloy, 0.05-0.12wt
A general lead calcium based alloy containing% Ca and 0.2 to 1.0 wt% Sn can be used.

The negative electrode plate 2 was manufactured by filling a casting grid made of an antimony-free lead alloy with an ordinary negative electrode paste containing a shrinkproofing agent such as lignin or barium sulfate. Lead alloy for negative electrode grid is 0.05 to 0.12 wt% Ca, 0.001 to 0.5 wt%
A general lead calcium alloy containing Sn can be used.

In this embodiment, cast grids were used for the positive and negative electrodes, but expanded grids or punched grids in which a lead alloy sheet is spread can be used. Also, the electrode plate filled with the storage battery paste is aged in a room at 30 to 80 ° C before use. In particular, aging of the positive electrode plate is an important step in battery performance.

Next, the sealed lead acid battery according to the present invention
6 A (0.2 C) discharge at ℃ and 150 A (5 C) discharge at -15 ℃ to perform capacity test, then J
A life test (discharge: 20 A × 1 h, charge: 5 A × 5 h, temperature: 40 ° C.) was performed according to the IS standard.

A conventional battery No. 1 in which a ribbed separator was used as the separator and granular silica was filled therein was used. 10 and the conventional retainer type battery No. 11 was also subjected to the same test.
Table 2 shows the test results.

[0032]

[Table 2]

Battery No. 1 using a porous sheet obtained by combining granular silica powder and a small amount of microporous polypropylene using a polyfluoropolymer as a binder according to the present invention as a separator. Nos. 2 to 9 are conventional battery Nos. Using a separator with ribs for the discharge capacity and the voltage at the 5th second. 10 and the conventional retainer type battery No. It showed an initial performance of more than 11.

The initial capacity of the battery of the present invention was superior to that of the conventional battery using the ribbed separator because the latter was insufficiently filled with the granular silica powder because the separator and the positive and negative electrode plates were too close to each other. Therefore, it is considered that the electrolytic solution was not retained in the portion not filled with the powder.
Furthermore, it is considered that the resistance of the separator was larger than that of the separator of the present invention.

The battery of the present invention has a larger initial capacity than the conventional retainer type battery because the former has a larger amount of electrolytic solution than the latter because it is filled with granular silica around the electrode plate group. This is because.

When microporous polypropylene is added to the separator raw material, it is superior to the one using only silica powder in the high rate discharge performance, because the former separator has a higher porosity than the latter, and therefore the electrolyte solution. It is thought that this was because a lot of

The life performance of the product of the present invention is the same as that of the conventional retainer type battery No. Compared with No. 11, excellent results of 1.5 times or more were obtained. This 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 considerably badly corroded the grid, but the electrode plate was hardly deformed. Instead, it is considered that the powder filled around the electrode plates strongly pressed the electrode plates to prevent their deformation, resulting in a long life.

[0038]

As described in detail above, according to the present invention, a lead-acid battery is characterized in that a polyfluoropolymer is used as a binder and silica powder and, in addition thereto, a small amount of microporous polypropylene are combined. A new sealed lead-acid battery can be easily manufactured by using the separator for the battery, and the initial and life performances can be greatly improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a sealed lead-acid battery using a separator of the present invention.

[Explanation of symbols]

 1 Positive Plate 2 Negative Plate 3 Separator 4 Battery Case 5 Battery Cover 6 Powder Layer 7 Foam 8 Exhaust Valve

Claims (1)

[Claims] 1. A separator for a lead storage battery, comprising a silica powder and a small amount of acid- and oxidation-resistant microporous resin powder bonded together using a polyfluoropolymer as a binder.