JPS63138649A - Enclosed lead storage battery - Google Patents

Abstract

PURPOSE:To prevent an active material from dropping off and improve the cycle life by coating both surfaces or one surface of at least one electrode of positive and negative electrode plates with graphite having a layer-like structure. CONSTITUTION:When both surfaces of positive and negative electrodes 2, 4 are to be coated with graphite 1 respectively, the electrodes 2, 4 are immersed in a liquid made by swelling polyvinyl alcohol in the pure water and diffusing graphite 1, for example. If the surface of the electrode plate is coated with graphite, the so called intercalation reaction in which sulfuric acid enters into or goes out of the graphite layer occurs on the surface of the electrode plate. Accordingly, the graphite 1 is not shrunk inside the active material, the deterioration of the binding force among active material grains and resultantly the dropping off of the active material can be prevented, and the long life of a battery can be obtained. In addition, a high-capacity battery is available by this intercalation reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to sealed lead-acid batteries, and is particularly suitable for improving the utilization rate of active materials.

This invention relates to improving the surface of negative electrodes.

Conventional technology In recent years, cordless devices with high power consumption, such as portable VTRs and small vacuum cleaners, have become popular.As a power source for these cordless devices, they can be used repeatedly and can handle large load currents. There has been a demand for secondary batteries that can provide stable performance in response to the demand for batteries, and with the spread of secondary batteries, highly safe and reliable sealed lead-acid batteries have been developed. The biggest technical challenge in sealing conventional lead-acid batteries is how to suppress all the gases generated during charging, and the methods described below are being used.

H2O−+ 2H”+MO2+2e −
−−−=(1) Pb+3AO2+H2Sod →PbS
O4+H20−−−−・(2)PbSOd+2H”+
2s-*Pb+H2So4-, (3) At the end of charging or during overcharging, an electrolysis reaction of water as shown in equation (1) occurs on the positive electrode. The oxygen gas generated here diffuses through the separator or the space inside the battery, reaches the negative electrode, and is reduced to water by the reaction shown in equation (2)K.

At the same time, lead sulfate is produced, but the lead sulfate at the negative electrode is reduced to lead by the charging reaction of equation (3). Since hydrogen ions are consumed in this reaction, generation of hydrogen gas on the negative electrode is prevented and sealing becomes possible.

One of the important components in completing this sealing is the separator. This separator has two distinct roles. The first is to hold the electrolyte and make it non-fluidized to eliminate leakage, and the second is to make it easier for oxygen gas generated at the positive electrode to diffuse to the negative electrode. In such a battery system, the amount of electrolyte is kept to a minimum in terms of leakage and gas diffusion. On the other hand, the charge/discharge reaction of a lead-acid battery is (
Positive electrode) (Electrolyte) (Negative electrode) As can be seen from this equation, sulfuric acid in the electrolyte is consumed during discharge. Therefore, minimizing the amount of liquid in order to improve leakage resistance and oxygen gas diffusivity greatly limits the discharge capacity of the lead-acid battery.

In addition, even if the concentration of sulfuric acid is increased and the amount of sulfuric acid is increased, the corrosion of the lattice becomes severe at high concentrations, and in practice, the sulfuric acid specific gravity is 1.
40 is the limit, and the concentration cannot be made too high. Therefore, when compared to conventional lead-acid batteries with a rich electrolyte, sealed lead-acid batteries have the same size.
Since there were few sulfate ions, there was a problem that the utilization rate of the active material was low. However, in order to solve this problem, it has been attempted to mix graphite into the positive electrode active material, and when charging, that is, when the sulfuric acid concentration is high, an interlayer compound of graphite and sulfuric acid is formed and sulfuric acid is incorporated between the graphite layers. Measures have been taken to suppress the sulfuric acid concentration in the electrolytic solution, and on the other hand, when the sulfuric acid concentration in the electrolytic solution becomes low during discharge, sulfuric acid is released from between the graphite layers to increase the discharge capacity. When moving in and out between 1-item layers, the inter-layer distance repeatedly changes from 3.35 people to 7.98 people, or from 7.98 people to 3.35 people. This expansion and contraction causes a decrease in the bonding strength between particles of the positive electrode active material, which in turn causes the active material to fall off, resulting in a decrease in cycle life.

Problems to be Solved by the Invention As mentioned above, sealed lead-acid batteries have the problem of limited liquid volume due to sealing, that is, a decrease in the active material utilization rate. Improvements have been made by incorporating graphite into the material. However, this method also has some problems, such as shrinkage of graphite, which reduces the bonding of active material particles, and also causes the active material to fall off, resulting in a short cycle life.

The present invention solves this problem by using graph 1a)1 in order to improve the active material utilization rate. However, the present invention aims to improve the cycle life without causing the active material to fall off. That is.

Means to solve problems In order to solve the above-mentioned problems, the present invention solves the above problems.

Graphite having a layered structure is coated on both surfaces of at least one of the negative polar plates.

Function As mentioned above, graphite incorporates sulfuric acid into its layered structure to form a graphite-sulfuric acid layered compound during charging when the electrolyte concentration is high or during overcharging, and conversely, sulfuric acid It has the property of releasing sulfuric acid and returning to graphite during discharge when the concentration of the electrolyte consumed by the reaction decreases, but as in the present invention,
If graphite is coated on the surface of the electrode plate, the so-called intercalation reaction, in which sulfuric acid moves in and out between the graphite layers, will occur on the surface of the electrode plate, so that shrinkage of the graphite will not occur inside the active material as in the conventional case. Therefore, it is possible to prevent a decrease in the bond between active material particles and to prevent the active material from falling off, thereby making it possible to extend the life of the battery. Furthermore, this intercalation reaction also enables higher capacity batteries.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

FIG. 1 shows a schematic longitudinal section of a cell of a sealed storage battery according to the present invention. In FIG. 1, 1 is graphite having a layered structure, that is, graphite.

The figure shows the coating on both sides of the positive and negative electrodes. Graphite) In this example, polyvinyl alcohol was swollen in pure water, and then bluffing liquid was dispersed therein, and the electrode was immersed in the liquid and then dried. In the case of this example, 0.02 (J/cr
I was able to apply f. 2 is a positive electrode, in which a lead lattice alloy is filled with an active material whose main component is Pbo2.

3 is a separator, which is made of a glass mat mainly composed of glass fibers, holds the electrolyte and makes it non-fluid, and is porous so as not to prevent the diffusion of oxygen gas generated from the positive electrode. 4 is a negative electrode, in which a lead lattice alloy is filled with an active material whose main component is lead. 6 is a battery case and is made of ABS resin, which has excellent sulfuric acid resistance.

6 is a safety valve that operates when the internal pressure of the battery rises above the operating pressure of the valve, releasing the internal gas and preventing the pressure from rising. It also prevents air from entering from outside.

As described above, the sealed lead-acid battery shown in this example has a 10% increase in discharge capacity and a 20% increase in cycle characteristics compared to conventional batteries of the same type, achieving higher capacity and longer life. .

Effects of the Invention As described above, the present invention not only makes it possible to increase the capacity and extend the cycle life of sealed lead-acid batteries, but also
Because graphite is a conductive powder and is present at the interface between the separator and the electrode plate, the internal resistance can be lowered compared to conventional products, and the discharge characteristics have also been improved.

[Brief explanation of the drawing]

The figure is a schematic cross-sectional view showing an outline of a sealed lead-acid battery according to an embodiment of the present invention. 1...Graphite having a layered structure, 2...
Positive electrode plate, 3... Separator, 4... Negative electrode plate, 6... Battery container, 6... Safety valve.

Claims (1)

[Claims] A sealed lead-acid battery characterized in that graphite having a layered structure is coated on one surface of at least one of the positive and negative polar plates.