JPH012255A - Negative electrode plate for sealed lead-acid batteries - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an improvement in a negative electrode plate for a sealed lead-acid battery of a negative electrode absorption type in which oxygen gas is absorbed at the negative electrode.

Conventional technology In recent years, along with the rapid miniaturization and portability of electronic devices, secondary batteries that can be recharged and used many times have been in the spotlight due to their economic efficiency and resource conservation. Demand is increasing. Small lead-acid batteries built into equipment must not leak overnight, no matter how tilted they are used. Therefore, a closed type structure is preferable, and a method in which a gelling agent is added to gel and fix the electrolyte, and a thick separator with a large porosity absorbs the electrolyte.

There is a retainer type in which the device is held, but recently the retainer type has been mainly used.

When a lead-acid battery is charged, lead sulfate turns into lead dioxide at the positive electrode, and lead sulfate turns into lead at the negative electrode. Then, when the lead sulfate of the positive and negative electrodes reaches lead dioxide and lead, and if charging continues, that is, in the case of overcharging, water electrolysis occurs, and oxygen gas is released from the positive electrode, and then the negative electrode. Hydrogen gas is generated.

Therefore, it is necessary to take measures to keep it airtight.

There are several methods of sealing.

■Third electrode method in which the capacity of the positive electrode is larger than that of the negative electrode so that during overcharging, hydrogen gas is first generated from the negative electrode, which is then reduced to water by the auxiliary electrode connected to the positive electrode.■Oxygen gas generated from the positive electrode and the negative electrode The catalyst plug method uses a gas-phase catalyst to convert the hydrogen gas generated from the gas into water using a gas-phase catalyst.■ The capacity of the negative electrode is increased above the positive electrode. Oxygen gas is first generated from the positive electrode, and this is absorbed by the negative electrode. There is a negative electrode absorption type that generates lead so that it is always in an uncharged state so that no hydrogen gas is generated, but recently the negative electrode absorption type has become mainstream.

Conventionally, this type of negative-cell absorption type sealed lead-acid battery has the following configuration. A positive electrode plate made of lead dioxide and a negative electrode plate made of lead are opposed to each other via a nonwoven separator made of fine glass fibers having a diameter of 1 to 10 microns entwined with an acrylic binder. And the electrolyte is l1fi
Since the liquid is absorbed and maintained by the separator to prevent the i-liquid from leaking, the separator requires a certain degree of thickness, which is more than % of the battery thickness. These electrode plates are inserted into a battery case made of propylene resin. Active material capacity of negative and positive electrodes;
A positive ratio has a larger negative electrode. Therefore, during overcharging, the positive electrode is first fully charged and oxygen gas is generated. Then, this oxygen gas diffuses through the separator and the battery case, reaches the negative electrode, and reacts with the negative electrode there, and the negative electrode becomes lead sulfate through lead oxide as described below.

Positive electrode H2O-1V202↓-2H++28-Negative electrode
Pb+I102-Sipb.

PbO + H2SO4 → Pb5Oa + H2O That is, lead sulfate is a discharge product of the negative electrode, and this reaction
As long as the negative 1 selection is sold, it will not reach a fully charged state and hydrogen gas will not be generated. Therefore, sealing becomes possible.

An example of manufacturing a conventional negative electrode plate will be described. A grid made of lead-calcium alloy is coated with a paste made by kneading approximately 10 micron lead powder with water and diluted acid, along with additives such as lignin and barium sulfate.

It is chemically modified and adjusted.

Problems to be Solved by the Invention With such a conventional configuration, when a large amount of oxygen gas is generated due to overcharging with a large current, the negative electrode plate can absorb oxygen gas only near the surface of the electrode plate. cannot keep up with charging, and the amount of lead sulfate reduced by charging becomes greater than the amount of lead sulfate produced by oxygen gas absorption. Therefore, the lead sulfate that had been added in a larger amount than the positive electrode is used up, and the negative +i becomes fully charged, hydrogen gas is generated, and the charge is 1! ! The internal pressure rises and oxygen and hydrogen gas are released from the safety valve. That is, water is electrolyzed and reduced, and the sulfuric acid concentration in the electrolyte increases. In this case, the viscosity of the electrolytic solution increases, making it difficult for the solution to become multivalent, resulting in poor release/ili characteristics, and when the concentration becomes high, the lattice becomes susceptible to corrosion.

The present invention solves this problem by first improving the absorption of oxygen gas generated from the positive electrode at the negative electrode during overcharging, thereby improving the overcharging characteristics at large currents, that is, the gas absorption of the negative electrode. The purpose of this is to improve one's ability.

Alternative Means for Solving the Problem In order to solve this problem, the present invention comprises a negative electrode plate made of water-repellent hollow fine fibers and lead powder.

Function: With this configuration, when the oxygen gas generated from the positive electrode plate reaches the surface of the negative electrode plate, it can diffuse into the interior of the negative electrode plate through the surface layer of the fine fibers and the hollow portion. Therefore, oxygen gas absorption, which could conventionally be carried out only on the surface of the negative electrode plate, can also be carried out inside the negative electrode plate, and the ability to absorb 1lI12 elemental gas is improved.

It's a waste, because the hollow part of the hollow fine fibers is also treated with water repellent treatment, so the electrolyte will not enter the hollow part and hinder the diffusion of oxygen gas into the inside of the negative electrode plate, so it will be a good oxygen source. This means that gas absorption can be performed.

Embodiment FIG. 1 is an enlarged sectional view of a portion of a negative electrode plate in an embodiment of the present invention. 1 is a lead active material, which is a spherical material with a particle size of 10 microns and is connected to a three-dimensional object. The surface is covered with the electrolytic solution 4 to form a liquid film.

Reference numeral 2 denotes a fine fiber made of glass, which has a diameter of about 10 microns and a length of 0.1 to 1 silk, and has a hollow portion 3 formed therein with a hole having a diameter of 1 to 6 microns. A water-repellent fluororesin 6 is coated on the surface of the fine fibers 20 and the hollow portion 3. The glass fine fibers are kneaded with the lead active material at a ratio of 0.1% by weight. At this time, the fine fibers only partially come into contact with the spherical lead active material, and the other parts are water-repellent, so they repel the electrolyte and form a gas phase 6 between them and the lead active material. . This gas phase portion 6 is continuous from the surface of the electrode plate to the inside of the electrode plate along the fine glass fibers. Therefore, oxygen gas can diffuse into the interior of the negative electrode plate through the gas phase portion along the fine fibers and the water-repellent hollow portion.

FIG. 2 shows a comparison of the gas absorption abilities of the negative electrode plate 7 of the present invention and the conventional negative electrode plate 8. That is, the graph shows the weight reduction when a battery with a capacity of 2Ah was prototyped and charged with an amount of electricity of 100Ah, which is equivalent to 50 times the battery capacity, using various charging currents. As mentioned above, weight loss is one means of evaluating the oxygen gas absorption ability of the negative electrode. The thickness of the battery is 1.5
My friend is vertical 4α.

It consists of two positive electrode plates with a width of 3 cr II and three negative electrode plates with a thickness of 1 mm, a length of 4 G+, and a width of 3 cr, and the positive electrode plate is sandwiched between the negative electrode plates. And between each electrode plate there are 1 to 10
A separator with a thickness of 1 mm and made of micron diameter glass fiber RLT is interposed.
．． 30) and 16 ml of sulfuric acid electrolyte. This corresponds to 11.7 g of water and 7.8 g of sulfuric acid. The above-mentioned 2Ah capacity [11] single cells were experimentally produced using the conventional negative electrode plate and the negative electrode plate of the present invention. And o,
oscA (1oomA), o, 1CA (200mA
), 0.3 CA (600mA), and 0.3 CA (600mA).
5CA (1ooomA) for 1000 hours and 600 hours.

Overcharging was carried out for 167 hours and 100 hours, that is, an amount of electricity of 100 Ah. The weight loss at that time is shown in Figure 2. The battery is equipped with a safety valve to prevent the battery from expanding or bursting due to the increase in internal pressure due to gas generation, but in this experiment the valve pressure was set to ν3 of 0.2.

As is clear from Fig. 2, the effect of improving the oxygen gas absorption ability with one negative electrode of the present invention can be seen, and in Q, 3CA charging, compared to the case where a conventional negative electrode plate was used! The amount of 1ffl is only 1ffl, and the oxygen gas absorption capacity has improved to 5 times.

As described above, according to the present invention, oxygen gas generated from the positive electrode during overcharging is diffused and absorbed into the inside of the negative electrode plate through the surface of the negative pupil plate, the glass fiber surface, and the hollow part, so that oxygen gas is absorbed. ability improves. In other words, the oxygen gas generated from the positive electrode during overcharging is quickly diffused and absorbed throughout the negative electrode plate, so the amount of oxygen gas absorbed per hour is reduced compared to the conventional negative electrode plate where the absorption was only on the electrode plate surface. Increase.

do. Therefore, the negative electrode can carry out the oxygen gas absorption reaction more quickly than before even if it is charged with a large current. The valve pressure of the safety valve is 0.2 kg/c, l! This is because the oxygen gas generated from the positive electrode plate at the beginning of charging reaches the negative electrode plate and it takes some time for the gas absorption cycle to reach a steady state, which may result in weight loss due to gas dissipation. It becomes less. When overcharged at 0.3 OA for 167 hours, if a conventional negative electrode plate is used, the electrolyte concentration will decrease by 57, and if water is reduced, the electrolyte concentration will increase to 54 Chi (specific gravity 1.43). In contrast, when using the negative electrode plate of the present invention, the electrolyte concentration decreases by 1 da and the electrolyte concentration only slightly increases to 42% (specific gravity 1.32). Therefore, it is possible to prevent deterioration of battery performance due to liquid reduction, and also to prevent corrosion of the grid due to increase in electrolytic solution.

Effects of the Invention As described above, according to the present invention, it is possible to provide a negative electrode plate for a sealed lead-acid battery with excellent overcharge characteristics.

[Brief explanation of the drawing]

Figure 1 is an enlarged sectional view showing a part of a negative electrode plate according to an embodiment of the present invention, and Figure 2 shows weight reduction during overcharging and idle time due to various charging currents when using the present invention and a conventional negative electrode plate. FIG. 1...Lead active material, 2...Fine fiber, 3...-
... Hollow part, 4... Electrolyte, 5... Fluorine, sodium chloride film, 6... Gas phase part. Name of agent: Patent attorney San Nakao and 1 other person/-
--giyu'4yJ member? ---Kakushoku pheasant, 3-m-Nakamuro@b 4-m-Electrolysis 1 night 5---Fu-) Series year's fly i trap Figure 1 6-Kibei name also Figure 2 Charging Electric Mi-en (CA')

Claims (1)

[Claims] 1. A negative electrode plate for a sealed lead-acid battery, comprising hollow fine fibers and lead powder, the hollow fine fibers being treated to be water repellent.