JP2794588B2 - Sealed lead-acid battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a sealed lead-acid battery.

2. Description of the Related Art There are two types of sealed lead-acid batteries of a type in which oxygen gas generated during charging of a battery is absorbed by a negative electrode, a retainer type and a gel type. In the retainer type, a mat-shaped separator (glass separator) made of fine glass fiber is inserted between the positive electrode plate and the negative electrode plate, thereby holding the sulfuric acid electrolyte required for discharge and isolating both electrodes. In recent years, it has been widely used as a backup power supply for portable devices and computers. However, the retainer type has the disadvantage that the discharge capacity is limited by the amount of electrolyte at low rate discharge because the glass separator is expensive and cannot hold a sufficient amount of electrolyte. Has become an obstacle.

On the other hand, the gel type is less expensive than the retainer type, but has a drawback that the battery performance is inferior to the liquid type and the retainer type.

Therefore, the present invention eliminates the above-mentioned disadvantages of the conventional sealed lead-acid battery, and provides a necessary and sufficient amount of sulfuric acid electrolyte for charging and discharging the battery in order to provide an inexpensive sealed lead-acid battery having excellent discharge performance. We have proposed a sealed lead-acid battery in which a porous silica powder filled and arranged around an electrode group is impregnated and held in a porous powder granulated using a binder. Several shortcomings became apparent during the course of experiments with this type of sealed lead-acid battery. That is, (1) it takes a long time to inject the liquid for impregnating and holding the electrolyte in the granulated powder.

(2) Due to the gas generated during charging, the granulated powder moves and gas accumulation is likely to occur. Further, the electrolytic solution is pushed out by the gas and overflows outside the battery case.

There is a disadvantage that.

Means for Solving the Problems The present invention is to eliminate the drawbacks of the sealed lead-acid battery obtained by impregnating and holding the above-described granulated powder with a sulfuric acid electrolyte, and the main point is that the inner surface of the battery case has a small area. In both cases, the porous sheet is brought into contact with one surface. Hereinafter, the present invention will be described based on examples.

Example The positive and negative electrode grids made of a Pb-Ca-Sn alloy were each filled with ordinary positive and negative electrode pastes and then aged to produce an unformed electrode plate. Next, using these positive electrode and negative electrode non-polarized electrode plates, an isolation rod shown in FIG. 1 was inserted between the two electrode plates to prepare an electrode plate group. The isolation bar 1 shown in the figure is formed by molding an acid-resistant synthetic resin into an E-shape, and the vertical isolation bar is corrugated. The electrode plate group was inserted into the battery case, and a glass mat as a porous sheet was previously brought into contact with the inside of the short side surface of the battery case, in this case, two inner surfaces corresponding to the side portions of the electrode plate. Here, any porous sheet may be used as long as it is hard to penetrate the granulated powder and has good acid resistance with good gas and liquid permeability.

Thereafter, a gap between the battery case and the electrode plate group and a gap between the electrode plates are filled with an electrolyte holder. This electrolyte holder was prepared as follows. First, a fine silica powder having a particle size of 10 to 40 millimicrons and methyl methacrylate as a binder
15% was added and kneaded with water, then granulated to a particle size of 100 to 200 microns and dried. The granulated silica powder is formed by agglomeration of silica fine primary particles into secondary particles of 100 to 200 microns, and the granulated powder itself is a free-flowing powder having a porosity of 85% or more.

 FIG. 2 shows a state in which the granulated silica powder is filled.

The silica powder was filled while applying vibration to the battery. As shown in the figure, the granulated silica powder was densely packed around the electrode group and between the electrode plates. Here, the granulated silica powder filled between the electrode plates also has the function of a separator. After filling the granulated silica powder, the lid was adhered and an exhaust valve was attached. The porosity in the filled state was about 90%.

Next, a sulfuric acid electrolyte was injected into the prototype battery. The test battery has a nominal capacity of 4.5 Ah. For comparison, a sealed lead-acid battery (filled with granulated powder without using a porous sheet on the inner surface of the battery case, using positive and negative plates of the same lot for comparison) A comparative product 1) and a conventional retainer type battery (comparative product 2) were also manufactured and tested. Table 1 shows the results.

As is clear from Table 1, the product of the present invention can inject the electrolytic solution in substantially the same time as the conventional retainer type battery (comparative product 2), and does not arrange a porous sheet on the inner surface of the battery case. The time was reduced to 1/10 of that of the product (Comparative Product 1). Also, as shown in Table 2, the battery performance was significantly improved as compared with the retainer type battery.

Further, the gas generated during charging comes to contribute to the hermetic reaction from the side of the electrode plate through the porous sheet, and therefore, it is less likely to push up the granulated powder or to form a gas reservoir.

Although the porous sheet used here was in contact only with two surfaces on the side of the electrode plate, an effect was recognized when the porous sheet was in contact with at least one surface. It was also effective to arrange a porous sheet above the filled granulated powder.

Effect of the Invention As is clear from the above-described embodiment, the retention of the electrolyte and the positive and negative
In a sealed lead-acid battery in which a negative electrode plate is isolated, contacting a porous sheet to the side surface of a battery case significantly reduces the time for injecting an electrolytic solution and improves battery performance.

[Brief description of the drawings]

FIG. 1 is a perspective view of an isolation rod, and FIG. 2 is a cross-sectional view of a sealed lead-acid battery according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Separating rod, 3 ... Battery case, 4 ... Negative electrode plate, 5 ... Positive electrode plate, 6 ... Granulated powder

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-57-65677 (JP, A) JP-A-61-198573 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 10/10-10/12

Claims (1)

(57) [Claims] In a sealed lead-acid battery in which oxygen gas generated during charging of a battery is absorbed by a negative electrode, a group of electrode plates having a predetermined interval between a positive electrode plate and a negative electrode plate is placed in a battery case. At the same time, a porous sheet is placed in contact with at least one of the inner surfaces of the battery case, and a silica fine powder of 10 to 40 millimicrons is bound around the gap between the positive electrode plate and the negative electrode plate and around the electrode group. A sealed lead-acid battery characterized by filling and arranging a porous powder granulated by using the above method, and impregnating and holding the granulated powder with a sufficient amount of a sulfuric acid electrolyte necessary for discharge.