JP2006128056A - Lead-acid battery and additive for lead-acid battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an additive for a lead-acid battery capable of recovering characteristics of a degraded lead-acid battery in an extremely short time and allowing the characteristics to last long. <P>SOLUTION: The lead-acid battery contains polyvinyl alcohol and at least one selected from a group composed of a single-layer carbon nanotube, a multi-layer carbon nanotube, a carbon nanohorn and a cabon nanofiber in an electrolyte and/or an electrode active material mold. The additive for the lead-acid battery contains polyvinyl alcohol and at least one selected from a group composed of a single-layer carbon nanotube, a multi-layer carbon nanotube, a carbon nanohorn and a cabon nanofiber. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a lead-acid battery and a lead-acid battery additive that have a large electric capacity and have a small decrease in electric capacity due to repeated charge and discharge.

In the lead storage battery, as the charge and discharge are repeated, lead sulfate crystals grow and the crystals become inactive. Therefore, the amount of the electrode active material decreases, and the capacity of the battery decreases. As a countermeasure, there is a method of charging lead sulfate for a long time with a small current to convert the lead sulfate back to metallic lead. However, this method is not effective because only a small part of the lead sulfate that has grown crystal becomes metallic lead. It was. In addition, there is a method of adding various additives such as fine carbon to the electrolytic solution, but the fine carbon is easily oxidized at the positive electrode and disappears in a relatively short time, and the effect is lost accordingly. There was a drawback. Further, a method for activating the deactivated lead sulfate by adding polyvinyl alcohol to the electrolytic solution and repeating charging / discharging has been proposed, but there is a drawback that it takes a long time to recover.

The present invention has found an additive for a lead storage battery that can restore the characteristics of a deteriorated lead storage battery in a very short time and maintain the characteristics for a long period of time compared to these conventional methods.
The first object of the present invention is to extend the charge / discharge cycle life of a lead-acid battery.
The second object of the present invention is to increase the capacity of the lead acid battery.
The third object of the present invention is to reduce the internal resistance of the lead acid battery.
The fourth object of the present invention is to restore the characteristics of a deteriorated lead acid battery in a short time.

The present invention relates to a lead storage battery comprising polyvinyl alcohol and at least one of the group consisting of a carbon nanotube single layer, a carbon nanotube multilayer, a carbon nanohorn, and a carbon nanofiber in an electrolyte and / or an electrode active material molded body, and polyvinyl alcohol And an additive for a lead storage battery comprising at least one of the group consisting of a carbon nanotube single layer, a carbon nanotube multilayer, a carbon nanohorn, and a carbon nanofiber, and for a lead storage battery in which the additive is dissolved or dispersed in water It is an additive.

The carbon nanotube single layer, carbon nanotube multilayer, carbon nanohorn, and carbon nanofiber used in the present invention have carbon atoms connected in layers, and electrons can move freely in the layer. Shows stability. In addition, since the size is as small as about 1 nanometer in diameter, it has a great effect of entering the surface and gaps of the electrode active material to form a three-dimensional network-like conductive path and assisting the exchange of electrons with the electrode active material. . The effect can be obtained even with a very small amount as compared with the case of using amorphous carbon fine particles such as conventional carbon black or graphite powder. In addition, since it is less susceptible to oxidation at the positive electrode than amorphous carbon fine particles, it is present in the electrolyte for a long period of time, so that the effect lasts for a long period of time.

The polyvinyl alcohol used in the present invention increases the hydrogen overvoltage in the negative electrode and suppresses the generation of hydrogen due to the electrolysis of water, so that the charging current is efficiently used for the reduction of lead sulfate, and the crystal of the negative electrode As a result of the progress of miniaturization, the large crystals of inactive lead sulfate are decomposed and activated.

In the present invention, the effect of using polyvinyl alcohol in combination with a single-walled carbon nanotube, a multi-walled carbon nanotube, carbon nanohorn, or carbon nanofiber is deep when conventional polyvinyl alcohol alone or a combination of polyvinyl alcohol and amorphous carbon fine particles is used. The internal resistance and capacity are finally recovered by repeating the charging / discharging as many as 5-10 times, whereas in the case of using both of the present invention, these functions are recovered with only 2-3 charging / discharging operations.

The polyvinyl alcohol used in the present invention preferably has a degree of polymerization of about 30 to 3000, and the concentration in the electrolyte is preferably in the range of 0.01 to 10%. In addition, the concentration of the carbon nanotube single layer, carbon nanotube multilayer, carbon nanohorn, or carbon nanofiber used in the present invention in the electrolyte is preferably about 1 / 1,000,000 to 1 / 10,000.

Using three lead storage batteries (48 volts) for battery forklifts that have been used every day for four years and whose working time has deteriorated to about half that of a new product, a: 0.1% added polyvinyl alcohol, b: 0.1% polyvinyl alcohol And 5% of carbon black pulverized product (prepared by the method of Japanese Patent No. 3341438), c: 0.1% of polyvinyl alcohol and 1 / 100,000 of carbon nanotube monolayer (invention) In each case, the number of times of charge / discharge until the electrolyte specific gravity was restored to the normal value (1.28 or more) by repeated deep charge / discharge was compared. The results are shown in Table 1.
Table 1 Comparison of number of charge / discharge cycles (electrolyte specific gravity after full charge before test: 1.18-1.22)
Additives Number of charge / discharge cycles (specific gravity of electrolyte after full charge after test: 1.28 or more)
a 8
b 6
c 3

Claims (3)

  A lead storage battery comprising polyvinyl alcohol and at least one of the group consisting of a carbon nanotube single layer, a carbon nanotube multilayer, a carbon nanohorn, and a carbon nanofiber in an electrolytic solution and / or an electrode active material molded body.   A lead-acid battery additive comprising polyvinyl alcohol and at least one of the group consisting of a carbon nanotube single layer, a carbon nanotube multilayer, a carbon nanohorn, and a carbon nanofiber.   An additive for a lead storage battery, wherein polyvinyl alcohol and at least one of the group consisting of a carbon nanotube single layer, a carbon nanotube multilayer, a carbon nanohorn, and a carbon nanofiber are dissolved or dispersed in water.