JPH06267524A - Sealed lead-acid battery - Google Patents

Abstract

PURPOSE:To realize a high rate discharge charasteristics and a long service life compatibly by making the ratio of the synthetic fiber of a separator which consists of a minute glass fiber and an acid-proof synthetic fiber having minute pores larger at the side contacting to a positive electrode plate than at the side contacting to the negative electrode plate. CONSTITUTION:By an acid-proof synthetic fiber having minute pores composing a separator provided between a positive and a negative electrode, the Sb fusing from the positive electrode is absorbed, and the deposition of the Sb to the negative electrode plate which consists of a lead alloy including no Sb is suppressed so as to prevent the solution and the reduction of an electrolyte owing to the generation of hydrogen gas, even though a Pb-Sb system alloy is used for a positive electrode grid. Furthermore, the ratio of the synthetic fiber at the side contacting to the positive electrode plate is made larger than at the negative electrode plate side, and thereby the Sb is stayed near the positive electrode plate and its transfer to the negative electrode plate is reduced. And since the Pb-Sb system alloy can be used as the positive electrode, the capacity is never reduced in the early period even though a thin electrode plate which can obtain a high rate discharge characteristics is used, and a long service life is realized.

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 gel type and a retainer type, in which a negative electrode reduces and absorbs oxygen gas generated during charging of the lead-acid battery.

The gel formula is dilute sulfuric acid and silicon dioxide (SiO ₂ ).
The electrolytic solution is made into a gel by mixing the fine powder of (1) to eliminate the fluid, which is cheaper than the retainer type, but has a drawback that the battery performance is inferior to the liquid type and the retainer type. On the other hand, in the retainer type, a mat-like separator (glass separator) mainly composed of fine glass fibers having a diameter of about 1 μm is inserted between the positive electrode plate and the negative electrode plate, and thereby the sulfuric acid electrolyte necessary for charging and discharging and the both electrodes are held. Has been widely used as a backup power source for portable devices and computers in recent years.

In such a sealed lead-acid battery, oxygen gas generated during charging is reduced and absorbed by the negative electrode to prevent decomposition and reduction of the electrolytic solution. However, antimony is deposited on the negative electrode grid and the negative electrode plate. When (Sb) is present, the hydrogen overvoltage of the negative electrode plate is lowered, hydrogen gas is likely to be generated from the negative electrode during charging, the electrolyte is decomposed and reduced, and the battery capacity is reduced early. Easier to do. Also,
When a grid made of a lead (Pb) -Sb alloy is used for the positive electrode plate, Sb is eluted due to corrosion of the positive electrode grid during use of the battery, and the eluted Sb moves to the negative electrode and is deposited on the negative electrode plate. Then, as described above, the hydrogen overvoltage of the negative electrode plate is lowered, hydrogen gas is easily generated from the negative electrode plate, the electrolyte is decomposed / reduced, and the problem that the capacity of the battery is lowered early is likely to occur. . For this reason, in the conventional sealed lead-acid battery, both positive and negative plates are alloys containing no Sb, mainly Pb.
-A lattice made of calcium (Ca) -based alloy is used.

Recently, there has been a demand for further improvement in the high rate discharge characteristics of sealed lead-acid batteries. For that purpose, it is necessary to narrow the gap between the positive electrode plate and the negative electrode plate. It is also necessary to make the negative electrode plate thin.

However, when a positive electrode plate, particularly a positive electrode plate made of an alloy not containing Sb such as a Pb-Ca-based alloy, is thinned, the capacity of the positive electrode plate is reduced early during a deep charge / discharge cycle, although the electrolytic solution is sufficient. There was a problem of lowering. If a Pb-Sb alloy is used for the positive electrode grid, it is possible to prevent such an early capacity decrease, but for the above reason, the Pb-Sb alloy cannot be used for the positive electrode, and it has excellent high rate discharge characteristics and long-term discharge characteristics. It has been difficult to obtain a sealed lead-acid battery that has a long life.

[0007]

According to the present invention, the positive electrode grid is P
In a battery made of a b-Sb-based alloy, a negative electrode grid made of a lead alloy containing no Sb, and a separator made of fine glass fibers and acid-resistant synthetic fibers having fine pores, in the separator on the side in contact with the positive electrode plate. The ratio of the acid-resistant synthetic fiber having fine pores is higher than the ratio of the acid-resistant synthetic fiber having fine pores in the separator on the side contacting the negative electrode plate. Since the synthetic fibers are not so well compatible with the electrolytic solution, it is preferable to subject the synthetic fibers to a hydrophilic treatment such as a sulfonation treatment or a plasma treatment.

[0008]

According to the present invention, even if a Pb-Sb-based alloy is used for the positive electrode grid, it is eluted from the positive electrode by the acid-resistant synthetic fiber having fine pores constituting the separator disposed between the positive electrode plate and the negative electrode plate. Sb is adsorbed, which suppresses the deposition of Sb on the negative electrode plate and prevents decomposition and reduction of the electrolytic solution due to generation of hydrogen gas. Furthermore, in this case, the proportion of the acid-resistant synthetic fibers having fine pores in the separator on the side contacting the positive electrode plate is more than the proportion of the acid-resistant synthetic fiber having fine pores in the separator on the side contacting the negative electrode plate. By increasing the amount of Sb as well, Sb is stopped near the positive electrode plate, and migration of Sb to the negative electrode plate is further reduced. In addition, since the Pb-Sb alloy can be used for the positive electrode, the capacity will not be reduced early even if a thin electrode plate is used, and the electrode plate can be made thin, so that high rate discharge characteristics are excellent. Become.

[0009]

EXAMPLES First, the batteries shown in Table 1 were produced.

[0010]

[Table 1]

The positive and negative electrode grids were both manufactured by gravity casting, and after casting, the positive and negative electrode pastes were kneaded and filled by a conventional method, and then aged and dried. Next, these positive and negative electrode plates were formed in dilute sulfuric acid, washed with water and dried after the formation was completed. After that, a battery was assembled by an ordinary method, diluted sulfuric acid having a predetermined concentration was injected, and supplementary charging was performed to complete a sealed lead acid battery having a capacity (10 hR) of 2 V and about 6 Ah.

Pb-Sb type alloy and Pb-Ca for the positive electrode
Pb-1.5 wt% Sb-0.15 for each type alloy
% By weight arsenic (As) -0.01% by weight selenium (Se) alloy and Pb-0.08% by weight Ca-1.5% by weight tin (Sn) -0.01% by weight aluminum (Al) alloy Pb-Ca based alloy of Pb-0.09% by weight
A Ca-0.01 wt% Al alloy was used.

Conventional glass fibers having a diameter of 0.8 micron were used as the fine glass fibers. Further, as a mixed paper separator of fine glass fibers and acid-resistant synthetic fibers having fine pores, conventional glass fibers having a diameter of 0.8 μm and polyethylene fibers having a diameter of about 25 μm having hydrophilic fine pores are used. A mixture obtained by mixing by weight was used. This polyethylene fiber has fine pores of about 0.03 to 1 micron, the porosity of this fiber is about 45%, and the specific surface area is about 4
It was 0 m ² / g. Furthermore, the ubiquitous proportion of polyethylene fibers was adjusted by the papermaking method, and the battery No. In the separator used in Example 1, 60% or more of the polyethylene fiber was contained in the thickness of 1/3 of the side in contact with the positive electrode. Battery No.
In the separator used in 2, the polyethylene fibers were mixed uniformly.

No. Positive electrode plate 6 for batteries 1-4
No. 7 and negative electrode plate 7 For the battery No. 5, three positive electrode plates and four negative electrode plates were used. The results of the initial capacity test are shown in Table 2.

[0015]

[Table 2]

The capacity of the conventional battery No. The capacity of 5 was set as 100 and shown as a relative value.

With a low rate discharge of about 0.1 C, No. 1 to
The battery No. 4 is a conventional battery No. The capacity was only increased by 5% from 5. It is considered that this is because although the utilization factor of the active material was improved due to the reduction of the current density due to the thin electrode plate and the doubling of the electrode plate area, the amount of the electrolytic solution was limited. . At high rate discharge of 5C, battery No. 1 using a large number of thin plates. The capacities of 1 to 4 are No. 1 using the conventional thick electrode plate. About that of 2.
It's six times bigger. This is because the surface of the electrode plate mainly reacts at the time of high-rate discharge, so that the electrode plate is thinner than the total amount of the electrolyte solution and the current density is reduced due to the electrode plate area being doubled. It is considered that the effect of the improved utilization rate is great.

Next, these batteries were subjected to the following life test.

Discharge 0.3CA to 1.7V Charge 2.5V (maximum current 1CA) for 5 hours Capacity test during life test Up to 1.0V at 5C (every 50 cycles) Temperature 25 ° C Capacity transition during life test Is shown in FIG.

No. The battery using the conventional thick electrode plate and separator of No. 5 had an initial capacity of about 8 even at the 300th cycle.
Although it had 0%, the initial capacity itself was no. It is only about 40% of 1, which is unsuitable for applications requiring good high rate discharge characteristics.

A thin Pb-Sb alloy grid is used for the positive electrode,
No. using a conventional fine glass fiber for the separator. The battery of No. 3 was No. 3 at the 150th cycle. About 4 of the initial capacity of 5
The capacity rapidly decreased to 0%. This is probably because Sb eluted from the positive electrode grid during the life test was deposited on the negative electrode plate, the hydrogen overvoltage was lowered, and the electrolytic solution was decomposed and reduced.

A thin Pb-Ca alloy grid is used for the positive electrode,
No. using a conventional fine glass fiber for the separator. The battery of No. 4 was No. 4 at the 100th cycle. About 6 of the initial capacity of 5
The capacity dropped sharply from 0% and N0.3 batteries. This is because the positive electrode grid is thin and Sb is not contained in the positive electrode grid. Therefore, in the cycle test including such deep discharge, the periphery of the positive electrode grid is preferentially discharged, and as a result, insulation around the grid is performed. It is probable that the discharge could not be performed even though a layer of conductive lead sulfate was formed and the unreacted active material remained.

On the other hand, a thin Pb-Sb alloy grid was used for the positive electrode, and for the separator, 20% by weight of polyethylene fibers having a diameter of about 25 microns having fine pores hydrophilized to the conventional fine glass fibers were mixed almost uniformly. Battery No. No. 2 was No. 2 even after 300 cycles. About 15 of 5
It had a capacity of 0%. This is because even if a Pb-Sb-based alloy is used for the positive electrode grid, the specific surface area of the polyethylene fiber having fine pores that constitutes the separator disposed between the positive electrode plate and the negative electrode plate is as large as about 40 m ² / g. As a result, Sb eluted from the positive electrode is adsorbed, which suppresses the deposition of Sb on the negative electrode plate, lowers the hydrogen overvoltage of the negative electrode plate, and decomposes / reduces the electrolyte due to the generation of hydrogen gas. It seems that I was able to prevent. Further, since the Pb-Sb alloy is used for the positive electrode, the capacity does not decrease early even if a thin electrode plate is used, and further, the high-rate discharge characteristics are excellent due to the thin electrode plate. It is thought that it has become.

However, here, the battery No. of the present invention in which the polyethylene fibers in the separator were made ubiquitous and the side containing much polyethylene was pressed against the positive electrode plate. In No. 1, No. 1 An even better capacity transition was observed with the No. 2 battery. This is because Sb is stopped in the vicinity of the positive electrode plate by making the proportion of polyethylene fibers in the separator on the side contacting the positive electrode plate larger than the proportion of polyethylene fibers in the separator on the side contacting the negative electrode plate, It is considered that this is because the transfer of Sb to the negative electrode plate was less.

The polyethylene fiber used in this example had a diameter of about 25 μm. However, in applications where there is a possibility of over-discharging, it is better to use a thinner fiber with a diameter of about 10 μm for more stable performance. To do. The mixing ratio of the glass fiber and the acid-resistant synthetic fiber in the whole separator is 5 to 70.
The effect was remarkable in the range of%.

[0026]

As described in detail above, in the battery according to the present invention, even if the Pb-Sb alloy is used for the positive electrode grid, the fine pores constituting the separator arranged between the positive electrode plate and the negative electrode plate are formed. The acid-resistant synthetic fiber having S adsorbs Sb eluted from the positive electrode and stops the adsorbed Sb in the vicinity of the positive electrode plate, which further suppresses the deposition of Sb on the negative electrode plate, thereby reducing the hydrogen overvoltage of the negative electrode plate. It is possible to prevent decomposition and reduction of the electrolytic solution due to the decrease and generation of hydrogen gas accompanying it, and since a Pb-Sb alloy can be used for the positive electrode,
Even if a thin electrode plate is used, the capacity does not decrease at an early stage, and since the electrode plate can be made thin, the high rate discharge characteristics are also excellent. As described above, the present invention makes it possible to provide a sealed lead-acid battery having excellent high rate discharge characteristics and long life, and its industrial value is very large.

[Brief description of drawings]

FIG. 1 is a diagram showing the transition of 5 CA discharge capacity during a life test.

Claims (2)

[Claims] 1. The positive electrode grid is made of a lead-antimony alloy,
In a sealed lead-acid battery in which the negative electrode grid is made of a lead alloy containing no antimony, the separator is made of fine glass fibers and acid-resistant synthetic fibers having fine holes, and the acid resistance having fine holes in the separator on the side in contact with the positive electrode plate. A sealed lead-acid battery characterized in that the proportion of the functional synthetic fibers is higher than the proportion of the acid-resistant synthetic fibers having fine pores in the separator on the side contacting the negative electrode plate. 2. The sealed lead-acid battery according to claim 1, wherein the acid-resistant synthetic fiber having fine pores is hydrophilized.