JP2002110220A - Lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead-acid battery capable of preventing occurrence of dendrite shorting in a conventional lead-acid battery, deterioration of high rate electric discharge characteristic, and layer formation phenomenon of electrolyte due to leaving it without using for a long time. SOLUTION: Sodium sulfate 7 is put on upper faces of a group of pole plates 2 of the battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a lead storage battery.

[0002]

2. Description of the Related Art In conventional lead-acid batteries, when the concentration of dilute sulfuric acid electrolyte decreases, lead sulfate, which is a discharge active material, dissolves and the Pb ²⁺ concentration increases, regardless of whether it is a liquid battery or a sealed battery. Therefore, the risk of so-called dendrite short-circuit, in which lead is electrodeposited in a dendritic manner at the negative electrode at the next charge and causes an internal short-circuit, increases. Factors that lower the electrolyte concentration include self-discharge due to long-term storage and overdischarge due to dark current. To avoid this danger, add sulfuric acid-soluble sulfates such as alkali metal sulfate, magnesium sulfate, and aluminum sulfate to the diluted sulfuric acid electrolyte without contributing to the charge / discharge reaction, There has been proposed a method of not lowering the concentration of NR more than a certain level.

[0003]

However, the addition of the above-mentioned readily soluble sulfate additive to the electrolytic solution increases the electric resistance of the electrolytic solution to deteriorate the high-rate discharge characteristics, or causes the lead grid or the like to deteriorate. There is a problem that it is unsuitable for use because it has large side effects, such as promoting corrosion of other lead components. In addition, the addition of the above-mentioned readily soluble sulfate causes an ionized state from the beginning, so that a stratification phenomenon of the electrolyte occurs during long-term use or during discharge, and the concentration of the electrolyte decreases from the upper part of the electrode plate group. There was a point. Such a problem is a problem commonly occurring in the liquid lead storage battery and the sealed lead storage battery. Therefore, it is desirable to solve the above problems of the conventional lead storage battery.

[0004]

SUMMARY OF THE INVENTION The present invention provides a lead-acid battery which solves the above-mentioned problems, and comprises:
It is characterized in that at least one kind of calcium sulfate is provided. According to the present invention, the lead storage battery of the present invention can be easily constituted, and the calcium sulfate is a molded product.

[0005]

[Action] The solubility product Ksp of calcium sulfate is 6 × 10^-Five
And the solubility product of lead sulfate, Ksp, is 2 × 10^-8Written in comparison to
Sulfuric acid, which causes dendrite short
Pb from lead²⁺Prior to the start of ionization,
Release Ca²⁺And SO_Four ^2-Can be supplied together with lead sulfate.
SO_Four ^2-Suppress ionization of lead sulfate by ionic effect
Therefore, generation of dendrite can be suppressed. Calcium sulfate
Is poorly soluble in acids, and the conventional soluble sulfuric acid
Extremely small solubility product compared to salt, electrolyte concentration
Almost no dissociation within normal range and extremely low electrolyte concentration
To increase the electrical resistance of the electrolyte for ionization
Never. Therefore, deterioration of high-rate discharge characteristics is prevented.
can do. In addition, calcium sulfate is
As it is hardly soluble in acid, it does not dissociate easily,
Because the ON supply is slow, the electrolyte stratification phenomenon easily occurs.
The electrolyte can be stratified by long-term discharge without shifting.
When the concentration of the upper part of the electrode group drops extremely due to
For example, when the concentration of the electrolyte drops due to over-discharge by dark current
Has an effect of preventing short circuit due to dendrite generation. Sulfuric acid
When calcium is formed into a plate, tablet, etc.
Easily and stably apply the desired amount on the top surface of the electrode group.
Can be installed in a state, dissociated SO_Four ^2-Is gravity
To move downward and supply smoothly when the electrolyte concentration decreases
As a result, stratification of the electrolyte can be prevented.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In a lead-acid battery according to the present invention, a group of electrodes is accommodated in a battery case comprising at least one cell chamber, and a desired amount of calcium sulfate is placed on the upper surface of the group of electrodes. As calcium sulfate, anhydrous calcium sulfate (CaSO
₄ ), calcium sulfate 0.5 hydrate (CaSO ₄ .0.5)
H ₂ O) and calcium sulfate dihydrate (CaSO ₄ · 2H
₂ O), at least one calcium sulfate selected from gypsum is provided. Thereafter, a predetermined amount of a dilute sulfuric acid electrolyte having a desired sulfuric acid concentration is injected. That is, in the liquid lead storage battery, the calcium sulfate is injected until it sinks below the electrolyte surface. In a sealed lead-acid battery, the electrode group is injected so as to impregnate the entire amount. The battery case of the lead storage battery thus obtained is covered with a battery case lid by a conventional method to complete a lead storage battery of a predetermined capacity. When a plurality of cell chambers are provided, it is a matter of course that a desired amount of calcium sulfate is placed on the upper surface of the electrode group housed in each cell chamber.

The above various calcium sulfate CaSO
₄ is manufactured by, for example, any well-known manufacturing method.
For example, it is obtained by adding sulfuric acid to a calcium salt such as calcium carbonate or calcium chloride. The shape of the calcium sulfate installed on the upper surface of the electrode plate group is powdery, amorphous mass, kneaded with water, molded into a mold having a desired shape, effect molded, and then removed from the molded product. Adopted arbitrarily. For the production of a molded product, for example, powder of anhydrous calcium sulfate or calcium sulfate 0.5 hydrate is kneaded with an appropriate amount of water, and this is molded into a mold having an appropriate shape and size such as cubic, rectangular, spherical, or plate-like. To produce a molded product made of calcium sulfate dihydrate, so-called gypsum obtained by reaction hardening. The plate-shaped molded body is convenient because a desired amount thereof is easily placed on the upper surface of the electrode plate group. When the calcium sulfate is in the form of powder, amorphous mass, small compact, tablet, etc., the desired amount may be directly placed on the upper surface of the electrode plate group, but innumerable on the shallow bottom wall whose upper surface is open. It is preferable to place it on the upper surface of the electrode plate group in a state where it is housed in a container having holes. The installed amount of calcium sulfate is, for example, 30 g / liter with respect to the electrolytic solution.

FIG. 1 is a perspective view in which a part of an example of a lead storage battery of the present invention is cut away. In the drawing, 1 is a battery case, 2 is a group of electrode plates housed in the battery case, 2a is a negative electrode plate, 2b is a positive electrode plate, 2c
Is a separator larger in size than the positive and negative electrode plates, 3 is a negative electrode strap connected to ears of the negative electrode plates 2a, 2a,..., 4 is a negative pole implanted on the upper surface of the negative electrode strap 3, 5 is positive electrode plates 2b, 2b. ,..., A positive electrode strap connected to the ears, and 6 denotes a positive electrode pole implanted on the upper surface of the positive electrode strap 5. Numeral 7 denotes calcium sulfate provided on the upper surface of the electrode plate group 2 according to the present invention. In the illustrated example, the molded body 7 is formed of a thick rectangular plate-like molded body 7 of calcium sulfate, and its both ends in the width direction face each other. A rectangular shaped body having a size suitable for being fixedly held between the positive and negative straps 3 and 5 on both sides is used. Next, after the calcium sulfate 7 is installed, a predetermined amount of a dilute sulfuric acid electrolyte having a normal sulfuric acid concentration is injected into the state in which the calcium sulfate 7 sinks below the surface of the electrolyte 8 as shown in the figure. Then, although not shown, a battery case lid is provided by a conventional method, and the positive electrode protruding from the upper surface of the battery case cover, and the upper end of the negative pole are positively fixed. Then, a lead-acid battery is completed as a negative electrode terminal. In the production of a sealed lead-acid battery, a retainer is used as a separator, a predetermined amount of an electrolyte is injected into the electrode group and impregnated, and then calcium sulfate 7 is placed on the upper surface of the electrode group, and the lower surface is placed on the lower surface. The upper edges of the separators 2c, 2c,.

[0009]

EXAMPLE A powder of calcium sulfate 0.5 hydrate (baked gypsum) was kneaded with an appropriate amount of water, placed in a mold of 20 × 30 × 5 mm, allowed to react and harden, and then taken out. Was prepared and prepared. Separately, the electrode group assembled by a conventional method was accommodated in a battery case, and then the above-mentioned calcium sulfate molded body was placed on the upper surface of the electrode group, and fixed between the positive and negative electrode straps on both sides thereof. Next, a predetermined amount of dilute sulfuric acid having a specific gravity of 1.24 was injected, and the calcium sulfate molded body was immersed in the electrolytic solution.
A liquid lead storage battery having a capacity of 2 V and a capacity of 10 Ah was produced. For comparison, a conventional liquid lead-acid battery having the same configuration as described above except that no calcium sulfate molded body was provided was also produced. After forming the above two-lead storage battery into a battery case, the high-rate discharge capacity of 3C was measured, and the battery of the present invention was the same as the conventional battery.
A capacity of 2 Ah was obtained and there was no difference. This is because, within the normal sulfuric acid concentration range, the amount of the poorly acid-soluble calcium sulfate, which is the agent of the present invention, is very small. This is considered to be because the increase in the electric resistance does not cause the deterioration of the high-rate discharge characteristics. Next, for each of the 100 lead-acid batteries, a resistance of 600Ω was connected at 40 ° C., and an overdischarge standing test was performed for 28 days, and the dendrite short-circuit occurrence rate (%) was compared by the subsequent charging. did. As a result, the short-circuit rate of the lead storage battery of the present invention was 0%, that is, no short circuit was recognized, whereas the short-circuit rate of the conventional lead storage battery was 65%. As described above, in the lead storage battery of the present invention, no short circuit was observed, and it was confirmed that the smooth supply of sulfate ions from calcium sulfate suppressed the dissolution of lead sulfate, and thus had a definite effect on dendrite growth. . On the other hand, the conventional lead-acid battery in which calcium sulfate was not installed exhibited the high short-circuit rate as described above. This is presumed to be due to the fact that the active material consumed sulfuric acid during overdischarge and the overall concentration decreased, and that the sulfate ion concentration above the electrode plate group extremely decreased due to stratification.

It has been found that the sealed lead-acid battery of the present invention also has the same effect as described above. In addition, in the lead storage battery of the present invention, corrosion of lead constituent members such as a lead grid, which was caused when a conventional readily soluble additive was used, was not observed at all.

[0011]

As described above, according to the present invention, since calcium sulfate is provided on the upper surface of the electrode plate group of the lead storage battery, battery short circuit due to dendrite short circuit can be prevented, high rate discharge characteristics can be maintained well, and long-term discharge characteristics can be maintained. The effect of preventing a decrease in the concentration of the electrolyte above the electrode group due to the stratification of the electrolyte during standing for a long period or during long-term use is provided.

[Brief description of the drawings]

FIG. 1 is a perspective view in which a part of a lead storage battery according to an embodiment of the present invention is cut away.

[Explanation of symbols]

 A Lead storage battery of the present invention 2 Electrode group 7 Calcium sulfate, molded body thereof 8 Electrolyte

Claims (2)

[Claims] 1. A lead-acid battery, wherein at least one kind of calcium sulfate is provided on an upper surface of an electrode group. 2. A lead-acid battery, wherein the calcium sulfate is a molded body.