JPS63126161A - Enclosed type lead storage battery - Google Patents

Abstract

PURPOSE:To improve charging in a high charging rate and liquid-keeping force of an electrolytic solution in an over charge, and to prolong a battery life by making a mean pore diameter of a surface part to be larger than that of the inner part of plates in a pore distribution in active materials of negative plates. CONSTITUTION:A negative plate 1 is provided which having a distribution in which a mean pore diameter of the surface part is made to be larger than that of the inner part of plates in the pore distribution of active materials constituting negative plates 1. Using such the negative plate 1, an oxygen gas diffused from through a separator 2 or passed from a space in a battery inner part is not only absorbed in the negative electrode surface but also easily diffuses in the plate inner part as the mean pore diameter is larger, and thereby an absorbing power of oxygen is improved. This allows not only a decreased liquid quantity in an overcharge is decreased and a longer life can be realized but also the life can be prolonged in a constant current charge by a high charging rate. And a liquid-keeping force of an electrolytic solution is improved as the pore diameter on the negative electrode surface part becomes larger, and discharging properties in the high charging rate is also improved as the diffusion of sulfuric acid is made easier than ever.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to a sealed lead-acid battery, and relates to a pore distribution particularly in the negative electrode, which improves the ability to absorb oxygen gas generated at the end of charging or during overcharging. This is related to the improvement of.

Conventional technology In recent years, cordless devices with relatively large power consumption, such as VTRs and small vacuum cleaners, have become popular. There has been a demand for secondary batteries that provide stable performance even under load currents, and sealed lead-acid batteries that do not leak and do not require water replenishment have been developed.

This is because a glass mat made of thin glass fibers is used as the separator, and this is impregnated with an electrolyte, that is, sulfuric acid, to make it non-fluid, making it possible to avoid various problems caused by leakage. . On the other hand, in order to achieve hermetic sealing, it is necessary to prevent a pressure increase inside the magnetic battery due to oxygen gas and hydrogen gas generated by electrolysis of water during the final stage of charging and during overcharging. Therefore, the pressure increase is prevented by an oxygen cycle reaction as shown in the following equation.

H2o→2H++1/2o2+2e・・・・・・・・・
...(1) Pb+1//202+H2SO4→Pb5
o4+H20...(2) PbSo4+2H++
2e→Pb+H2So4・・・・・・・・・・・・(3
) In other words, at the end of charging or overcharging, the formula (1
) electrolysis of water occurs, and oxygen gas is generated on the positive electrode. This oxygen gas reaches the negative electrode by diffusion, and is reduced to water on the negative electrode by the reaction shown in equation (2). At the same time, lead sulfate is generated, but the lead sulfate is reduced to lead by the charging reaction of equation (3). This reaction of formula (3) consumes the hydrogen ions produced by the reaction of formula (1), thereby preventing the generation of hydrogen gas on the negative electrode.
It becomes possible to seal lead-acid batteries. In order to improve the reliability of this sealed lead-acid battery, it is necessary to ensure that the reactions of formulas (1) to (3) above occur efficiently. To this end, the reaction process in which oxygen gas is absorbed by the lead of the negative electrode, as shown in equation (2), is particularly important. Oxygen gas diffuses through the interior of the separator and the space inside the storage battery, reaches the surface of the negative electrode from the positive electrode, and an oxygen absorption reaction occurs on the negative electrode. On the other hand, the negative electrode active material has a uniform pore distribution from the outside to the inside of the electrode plate because it is obtained by kneading lead powder prepared to an appropriate particle size, coating it on the lattice, and chemically forming it. ing.

Generally, the average pore diameter of these pores is 0.1 to 1 μm, and the electrolyte is also held inside these pores, and the average diameter of these pores is 0.1 to 1 μm.
With an average pore diameter of , the diffusion of oxygen gas into the inside of the negative electrode is insufficient, and the oxygen gas absorption reaction takes place on the surface of the negative electrode. Therefore, the gas absorption ability of the negative electrode is restricted, and when the charging current exceeds a certain level, it becomes impossible to absorb all the oxygen gas generated during overcharging at the end of charging, and the internal pressure of the battery rises. Sealed lead-acid batteries are equipped with a safety valve to prevent internal pressure from rising. Oxygen gas dissipates through this valve, resulting in a decrease in water content in the shoulder fluid, which can shorten battery life. was.

Problems to be Solved by the Invention In such a conventional configuration, an oxygen gas absorption reaction occurs on the surface of the negative electrode, which limits the oxygen absorption ability, resulting in problems such as charging at high charging rates and overcharging. There is a problem in that the amount of electrolyte in the battery decreases and the life of the battery decreases accordingly.

The present invention aims to solve these problems by improving the oxygen gas absorption ability of the negative electrode.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention distributes the pores of the active material of the negative electrode plate so that the average pore diameter on the surface portion of the electrode plate is larger than that inside the electrode plate. It is something that

Function When using a negative electrode plate configured in this way, oxygen gas that has diffused in the separator or passed through the space inside the battery is not only absorbed on the negative electrode surface, but also has an average pore diameter of This makes it easier to diffuse into the inside of the electrode plate, improving its ability to absorb oxygen. Therefore, the cycle of the above formulas (1) to (3) occurs efficiently, and the decrease in electrolyte solution is suppressed.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a schematic longitudinal sectional view of a cell of a sealed lead-acid battery in an embodiment of the present invention. 1-a in FIG.

and 1-b are lead-based negative 4 active materials according to the present invention, and 1-a has a large average pore diameter,
In the case of this example, the average pore diameter is 5 to 1 ol 1 m.

On the other hand, 1-b is a portion having a smaller average pore diameter than 1-aL, and in the case of this example, has an average pore diameter of 0.1 to 1 μm. With these 1-a and 1-b, the negative electrode plate 1
It consists of In order to form portions with different average pore diameters in this way, when filling the negative electrode active material into the negative electrode lattice, the process is divided into two steps, and during the first filling, the pressure applied to the active material is increased. This is possible by reducing the pressure applied to the active material during the second filling. 2 is a separator made of thin glass fiber. This has the property of retaining the sulfuric acid electrolyte and also has permeability to oxygen gas generated from the positive electrode. 3 is a positive electrode, PbO2
is the main component. 4 is a battery case, which is made of ABS resin having sulfuric acid resistance. Reference numeral 5 denotes a safety valve, and a protrusion provided at the top of the battery case 4 is covered with a rubber cap. This operates when the pressure inside the battery rises, and its role is to remove gas from inside the battery. Normally, the inside of the battery case 4 is kept at a reduced pressure and has a sealed structure.

Figure 2 shows 400 mA from a fully charged state for a battery with a capacity of 2 Ah at a 10 hour discharge rate.

The amount of liquid loss [%] when overcharging was performed at 100 mA was plotted against the overcharging time, and the product of the present invention and the conventional product were compared. At low currents, there is little oxygen gas generated during overcharging, so there is no difference in the amount of liquid loss between the inventive product and the conventional product in terms of the absorption capacity of the negative electrode.However, at high currents, the gas absorption capacity of the inventive product decreases. Since this is large, the amount of liquid loss can be reduced.

Effects of the Invention As described above, according to the present invention, in order to increase the oxygen gas absorption ability, a negative electrode plate is used in which the average pore diameter of the surface portion of the electrode plate has a narrower distribution than that of the inside of the plate. Not only can the amount of fluid lost during overcharging be reduced and the battery life be extended, but also, as is clear from FIG. 2, the battery life can be extended even in constant current charging at a high charging rate. In addition, the pore size on the surface of the negative electrode increases, which increases the electrolyte's ability to hold the electrolyte, making it easier for sulfuric acid to diffuse than before, resulting in improved discharge characteristics at high charging rates. .

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an outline of a sealed lead-acid battery according to an embodiment of the present invention, and FIG. 2 is a comparison diagram plotting the amount of liquid loss against overcharge time when charging at 400 mA and 100 mA. 1...Negative electrode plate, 1-a...Negative electrode active material having large average pores, 1-b...Negative electrode active material having small average pores, 2. ... Separator, 3 ... Positive electrode plate, 4 ... Battery case, 6 ...
····safety valve. Name of agent: Patent attorney Toshio Nakao and one other person
, One φ Nobumi taste IAmusu

Claims (1)

[Claims] 1. A sealed lead-acid battery comprising a negative electrode plate having a pore distribution of an active material constituting the negative electrode plate such that the average pore diameter on the surface portion is larger than that inside the electrode plate.