JP3388265B2 - Lead-acid battery separator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a separator for a lead-acid battery. 2. Description of the Related Art There are two types of sealed lead-acid batteries using a so-called oxygen cycle in which oxygen gas generated during charging of a battery is absorbed by a negative electrode, of a retainer type and a gel type. Rete
The mat type separator made of fine glass fiber inserted between the positive electrode plate and the negative electrode plate (glass separator)
(2) to maintain the sulfuric acid electrolyte necessary for charging and discharging the battery and to separate the two electrodes.
Taking advantage of such features as portable power equipment, cordless equipment, and computer backup power supplies in recent years,
It has also been used for large stationary batteries and for starting automobile engines. [0003] However, the glass separator is made by forming a very fine glass fiber having a diameter of about 1 micron manufactured by a special method into a mat shape, and is compared with a separator commonly used for lead-acid batteries. In order to obtain the target battery performance, the electrode group must be strongly pressed and assembled into the battery case, and it is difficult to insert the electrode group into the battery case. This requires a lot of trouble, and inevitably increases the manufacturing cost of the battery. In addition, the closed-type lead-acid storage battery has a small amount of sulfuric acid electrolyte that can be held in the glass separator, and has a lower battery capacity, especially low-rate discharge capacity, than an open-type general lead-acid storage battery with abundant electrolyte. Was inferior. [0004] In order to improve the discharge capacity by using a glass separator having a large gap and a large thickness to hold as much electrolyte as possible on the glass separator, the internal resistance of the battery becomes large and the discharge capacity increases. When a thin glass separator is used to improve the voltage characteristics, on the contrary, when the thin glass separator is used, the electrolyte required for discharging cannot be secured, and the glass separator has a large porosity and a large pore diameter. In addition, there is a problem that a short circuit is likely to occur in the separator and the life is short. On the other hand, the gel type is a sealed lead-acid battery in which a sulfuric acid electrolyte is gelled with colloidal silica or water glass. However, the sulfuric acid separates and leaks, and the mobility of sulfate ions in the gel is reduced. The battery performance is poor due to poor battery performance, and the gel electrolyte has no gas passage for the oxygen gas generated at the positive electrode to reach the negative electrode. There was a drawback that the oxygen absorption reaction in the negative electrode did not occur until cracks were formed. Therefore, in order to solve the above-mentioned drawbacks of the conventional sealed lead-acid battery, a granular silica powder obtained by aggregating and granulating fine silica powder is used not as a retainer type but as a gel type rather than a retainer type. However, a sealed lead-acid battery has been proposed. This is a new configuration in which coarse secondary particle powder (hereinafter abbreviated as silica powder) formed by agglomeration of fine primary particles of hydrous silicon dioxide is filled between positive and negative electrode plates and around the electrode plate group. In a sealed lead-acid battery, it is possible to impregnate the powder with a sufficient amount of electrolyte so that the discharge capacity of the battery is not limited by the amount of electrolyte, and to fill the powder layer surrounding the electrode plate. To prevent deformation of the active material due to discharge,
It has become possible to significantly improve the initial performance and life performance of sealed lead-acid batteries. [0007] However, the above-mentioned novel sealed lead-acid battery has various problems that must be solved. That is, in order to obtain the expected battery performance of this new sealed lead-acid battery, the silica powder must be densely packed with a uniform thickness between the positive and negative electrodes. For this purpose, for example, a separator having a constant thickness as described in JP-A-2-165570 or a thin separator with a rib as described in JP-A-4-51470 is used. The silica powder is filled between the electrodes and around the electrode group while applying vibration to the battery assembled 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, the pole plate itself is not necessarily flat, but is bent or warped. By the way, there was a risk of a short circuit occurring. Therefore, in consideration of safety, the gap must be increased inevitably. If the gap is increased, the internal resistance increases and it is not possible to manufacture a battery having good high-rate discharge performance. On the other hand, when a separator with ribs is used as in the latter example, there is a disadvantage that the resistance of the powder layer is added to the resistance of the separator, and the voltage characteristics particularly during high-rate discharge are deteriorated. In addition, when the silica powder is not sufficiently filled, there is a fatal drawback that the expected battery performance cannot be obtained. In any case, a special apparatus is required for manufacturing the electrode group. In addition, there is a major problem in battery production that it takes a long time to fill the powder between the narrow poles. SUMMARY OF THE INVENTION The present invention has solved the above-mentioned drawbacks of the novel sealed lead-acid battery. The gist of the present invention is to combine a polyfluoropolymer as a binder with silica powder. It is an object of the present invention to use a separator for a lead-acid battery, wherein acid-resistant synthetic fibers or glass fibers are added in an amount of 0.5 to 5% by weight of the silica powder. The separator for a lead-acid battery according to the present invention uses the powder constituting the separator as an electrolyte holder, but the powder and the added fibers are bound by a binder to form an elastic sheet. Therefore, the battery can be assembled in the same manner as in the case of using the conventional sheet-like separator, the productivity of the battery is improved, and the risk of a short circuit is eliminated because the interval between the electrode plates is constant. Furthermore, since there is only a powder layer between the electrode plates, no useless resistance is generated, and the use of the separator of the present invention can provide a battery having excellent initial and life performance.
In addition, the separator of the present invention has the advantage that the mechanical strength and flexibility of the separator are improved by the addition of acid-resistant synthetic fiber or glass fiber, which makes the work of assembling the battery even easier and allows a variety of assembling. There is. EXAMPLE A separator for a lead storage battery according to the present invention was produced 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 primary particles of 10 to 40 nm aggregate to form coarse secondary particles of 50 to 400 μm, was prepared. As the granular silica powder, a commercial product produced by spray-drying silica sol was used. Six kinds of mixed powders shown in Table 1 were prepared by changing the amount of the synthetic fiber added to the granular silica powder. Polypropylene (PP) fibers having a thickness of about 20 μm and cut to a length of 3 mm were used as the synthetic fibers used here. [Table 1] Next, 100 g of the mixed powder was put into a kneader, and polytetrafluoroethylene (PTFE) was used as a polyfluoropolymer. This was diluted by adding 300 g of water to 20 g of an aqueous suspension containing 30% by weight. This was added to the mixed powder in the kneader and kneaded sufficiently. At the beginning of kneading, the contents in the kneading machine are relatively non-sticky, but eventually exhibit rubber elasticity. In such a state, the contents are taken out and formed into a sheet having a thickness of 1.00 mm through a pair of rolls.
When dried at ℃, a sheet having relatively strong and cushioning properties was obtained. This was cut into predetermined dimensions to produce a separator. The density of the separator thus produced was 0.33 to 0.36 g / cm ³ , and the porosity was about 85 to 87%. The porosity could be controlled to some extent by the added water, the degree of kneading, the degree of pressing when passing through a roll, and the like, and the porosity could be further improved. The tensile strength of the above-described separator for a lead battery was measured according to JIS C 2313 (separator for lead-acid battery) 7.2.
FIG. 2 shows the results measured according to the tensile strength test described in Section 3. Subscripts in FIG. 2 indicate No. in Table 1. As can be seen from FIG. 2, the addition of polypropylene significantly increases the strength of the separator. Further, the addition amount is required to be at least 0.5%. If the addition amount is less than 0.5%, it is difficult to find the effect of the addition. Further, when the addition amount is 5%, the tensile strength becomes almost constant. It does not lead to an increase in When the separators (1 to 6) were assembled as an actual separator of a lead-acid battery, the separators No. 1 and 2 were assembled only as shown in FIG. However, since the separators Nos. 3 to 6 had high strength and flexibility, the separators could be assembled in a waveform as shown in FIG. Further, using the above-described separator for a lead storage battery, the battery No. 1 to 6 were assembled and the performance was examined. FIG. 1 is a sectional view of a main part of a sealed lead-acid battery using the lead-acid battery separator shown in Table 1, (A) is a front view,
(B) is a side view. First, the positive electrode plate 1 and the negative electrode plate 2 and Table 1
And the separator 3 shown in FIG. No special equipment was required to manufacture the electrode group, and the conventional assembly equipment could be used as it was. Next, after the prepared electrode group was inserted into the battery case 4, silica powder 6 having the same characteristics as those used for manufacturing the separator 3 was filled around the electrode group. Insertion of the electrode group into the battery case was extremely easy because there was no need to apply much pressure on the electrode group. In the present invention, since it is only necessary to fill the silica powder around the electrode plate group, the time required for filling the powder is only about one minute, and the time required for filling the powder can be greatly reduced. did it. The battery after the filling of the powder was filled with an open-cell phenol resin foam block 7 on top of the powder layer 6 to fix the powder layer 6. The battery case lid 5 is welded to the battery case 4,
Inject a predetermined amount of sulfuric acid electrolyte from the liquid port, attach the exhaust valve 8,
The battery was further charged to complete a 12 V battery having a capacity of about 30 Ah. The positive electrode plate 1 used was a casting grid made of an antimony-free lead alloy filled with a positive electrode paste. As an antimony-free lead alloy, 0.05 to 0.
A general lead-calcium alloy containing 12 wt% Ca and 0.2 to 1.0 wt% Sn can be used. The negative electrode plate 2 was manufactured by filling an ordinary negative electrode paste obtained by adding a shrink-preventing agent such as lignin or barium sulfate to a cast lattice using an antimony-free lead alloy. The lead alloy of the negative electrode grid is 0.05 to 0.12 wt% Ca, 0.001 to 0.5 wt% Sn
A general lead-calcium-based alloy containing In this embodiment, the casting grid is used for the positive electrode and the negative electrode. However, any of an expanded grid or a punched grid obtained by expanding a lead alloy sheet can be used. The electrode plate filled with the battery paste is used after aging in a room at 30 to 80 ° C. 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 is
6A (0.2C) discharge at ℃, then life test according to JIS standard (discharge: 20A × 1h, charge: 5A ×
5 h, temperature: 40 ° C.). Table 2 shows the results. [Table 2] From Table 2, it was found that the batteries Nos. 3 to 5 of the present invention were superior in both the discharge capacity and the number of life cycles to the battery No. 1 in which no polypropylene was added. Battery No. 6 to which 10% of polypropylene was added had poor discharge capacity and poor life cycle count. This is considered to be because addition of as much as 10% of polypropylene to the silica powder interferes with the intended purpose of the silica powder in retaining the electrolyte. In the present embodiment, polypropylene is used as the fiber mixed in the silica powder. However, an acid-resistant synthetic fiber such as polyester or polyacrylonitrile or a glass fiber has a sufficient effect. Further, the same effect can be obtained by using diatomaceous earth or a mixture of diatomaceous earth and silica powder instead of silica powder as the electrolyte retaining material. As described above in detail, according to the present invention, a silica powder is bound by using a polyfluoropolymer as a binder, and a synthetic fiber or a glass fiber is added to the silica powder. It is effective in improving the tensile strength of the lead-acid battery, and furthermore, the use of the separator of the present invention in a lead-acid battery makes it possible to easily produce a new sealed lead-acid battery, and furthermore, the initial and life performance can be significantly improved. It is now possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a main part of a sealed lead-acid battery using the separator of the present invention. FIG. FIG. 4 shows an electrode group using the separator of the present invention. [Description of References] 1 Positive electrode plate 2 Negative electrode plate 3 Separator 4 Battery case 5 Battery case lid 6 Powder Layer 7 Foam 8 Exhaust valve

Claims (1)

(57) [Claims] (1) Silica powder and 0.5 to silica powder.
~ 5% by weight of acid-resistant synthetic resin fiber or glass fiber;
Separator having polyfluoropolymer binder
An electrode plate group in which positive and negative electrode plates are laminated via
And silica powder filled around.
Lead-acid battery.