JPH0654661B2 - Sealed lead acid battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sealed lead acid battery, and more particularly to improvement of cycle life characteristics during rapid charging.

[Prior Art] In a sealed lead acid battery, an electrolytic solution is absorbed and retained in a non-woven fabric or woven fabric of glass fibers called a retainer and an active material of an electrode plate. Further, since it is a cathode gas system, oxygen gas generated from the positive electrode plate is absorbed by the negative electrode plate and returns to water. In this way, the airtightness is maintained by the oxygen cycle in which oxygen gas does not escape to the outside of the lead storage battery. Therefore, when the sealed lead-acid battery is used, the orientation is free and it can be used in a state of being laid sideways. Moreover, it has an advantage that no replenishing water is required. Sealed lead-acid batteries that have such advantages are used for cycle service such as power supply for portable cleaners such as hand cleaners and electric tools used for cleaning, for cycle service applications, or during power outages. It is widely used for float service applications where float charging is performed, such as a backup power source for equipment.

[Problems to be Solved by the Invention] Charging of this type of sealed lead-acid battery for the above cycle service use is normally completed in about 4 hours by constant voltage charging or quasi-constant voltage charging. However, recently, it has been required that even this type of battery can be rapidly charged in about 60 to 90 minutes. When performing rapid charging, it is necessary to supply a large amount of electricity to the lead storage battery in a short time, and it is necessary to increase the charging current value as compared with the normal charging method. However, when the charging current value is increased, the charging overvoltage of the electrode plate is increased accordingly, so that electrolysis of water is more likely to occur as compared with the normal charging method. Then, the oxygen absorption reaction rate on the negative electrode plate is delayed as compared with the oxygen gas generation rate from the positive electrode plate during charging, the charging overvoltage of the negative electrode plate is increased, and hydrogen gas is generated. The generation of this hydrogen gas rapidly occurs at the time of charging 85% to 90% of the amount of discharge, and thereafter, charging is performed while generating hydrogen gas,
Charging efficiency becomes poor. The generation of hydrogen gas from the negative electrode plate prevents efficient charging and pushes out the electrolytic solution in the electrode plate, so that the content of the electrolytic solution in the negative electrode plate becomes small and the hydrogen gas is generated by discharge. It becomes difficult to charge the lead sulfate or the lead sulfate generated by the oxygen absorption reaction. Therefore, there is a problem that the amount of lead sulfate that is not charged increases and the capacity decreases as the charging and discharging are repeated.

An object of the present invention is to provide a sealed lead-acid battery that can improve cycle life characteristics when it is charged rapidly.

[Means for Solving the Problems] In order to solve the above problems, the present invention uses a negative electrode plate in which crystalline lead sulfate is present inside the surface portion of the negative electrode active material layer.

When the negative electrode active material layer is manufactured by dividing into two layers, and the crystalline lead sulfate is contained in the inner layer on the side close to the current collector, the crystalline lead sulfate can be easily and controllably added to the negative electrode active material layer. It can be present inside rather than on the surface.

[Operation] The cause of deteriorating the charging efficiency of the negative electrode plate at the time of rapid charging of the sealed lead-acid battery is the above-described generation of hydrogen gas. In order to suppress this, the charging overvoltage of the negative electrode plate at the time of charging may be suppressed to be low to facilitate charging. As a method of suppressing the charge overvoltage of the negative electrode plate, there is a method of leaving lead sulfate in the negative electrode plate. However, even if lead sulfate is left in the active material of the negative electrode plate, lead sulfate is reduced to lead during repeated charging, and the effect does not continue. Therefore, in the present invention, it has been decided to make the crystalline lead sulfate, which is difficult to reduce, exist inside the active material of the negative electrode plate.

When crystalline lead sulfate is allowed to exist on the surface portion of the active material layer of the negative electrode plate, the reaction area of the negative electrode plate becomes small, so that the overvoltage during charging rises and hydrogen gas generation cannot be suppressed. Also, since the discharge reaction occurs from the surface of the negative electrode plate,
The presence of crystalline lead sulfate on the surface also causes a decrease in discharge capacity. Therefore, the above-mentioned crystalline lead sulfate is allowed to exist inside the surface portion of the negative electrode active material layer. By doing this, the discharge capacity of the sealed lead-acid battery is
Since it is dominated by sulfuric acid in the solution, it does not reduce the discharge capacity of the negative electrode plate. Further, since crystalline lead sulfate is difficult to reduce, overvoltage during charging can be suppressed to be low for a long period of time, and generation of hydrogen gas from the negative electrode plate can be suppressed.

[Examples] Examples of the present invention will be described in detail below.

When manufacturing the negative electrode plate used in one embodiment of the present invention,
First, lead oxide, barium sulfate, an organic additive, and hard-to-reduce crystalline lead sulfate were kneaded with water and dilute sulfuric acid to form a paste, which was filled in a predetermined amount in a Pb-Ca alloy lattice to form an inner layer. To form. The filling amount at this time is half the final filling amount as the negative electrode plate. next,
Lead oxide, barium sulfate, and an organic additive are kneaded with water and dilute sulfuric acid to form a paste, which is filled onto the previously filled inner layer to form a surface layer. In this way, by filling the lattice base with two kinds of pastes, a negative electrode plate containing crystalline lead sulfate that is difficult to reduce inside the negative electrode active material layer is manufactured.

Then, this negative electrode plate was formed into a test negative electrode plate by a conventional manufacturing process. The amount of crystalline lead sulfate added to the inner layer of the test negative electrode plate used in the test was 20 wt% by weight. For a rapid charge / discharge cycle life test, a matte separator (retainer) made of glass fiber is placed between the negative electrode plate and the positive electrode plate to form a plate group, and the plate group is stored in a battery case. 12 V, 3 Ah (20 hours rate) sealed lead acid battery was prepared. For comparison, a 12 V, 3 Ah (20 hour rate) sealed lead-acid battery using a conventional negative electrode plate containing no crystalline lead sulfate was prepared.

A rapid charge / discharge cycle life test was performed using the sealed lead-acid battery A of the example of the present invention and the conventional sealed lead-acid battery B thus manufactured. The test conditions are 6A (2C
After discharging to 1.6 V / cell with the constant current of A), limit voltage
A constant voltage charge of 2.7 V / cell and a limiting current of 3 A (1 CA) was performed as a cycle of charging until the charge amount reached 105% of the discharge amount, and this charge cycle was repeated a predetermined number of times. The results of this comparative test are shown in FIG. First
As is clear from the figure, the sealed lead-acid battery A of the present invention is
Compared with the conventional sealed lead-acid storage battery B, the number of cycles until the discharge capacity ratio, which is a criterion for life determination, becomes 50% or less increases by 200 times or more. Therefore, it can be seen from this point that according to the present invention, the life performance of the battery is improved.

Further, FIG. 2 shows the charging characteristics at the time of rapid charging. Second
As can be seen from the figure, the sealed lead-acid battery A of the present invention takes a longer time to reach the limit voltage than the conventional sealed lead-acid battery B. This means that the charge overvoltage of the negative electrode plate is unlikely to rise, and means that the generation of hydrogen gas from the negative electrode plate is suppressed. Therefore, it is considered that this affects the life performance. Thus, it was confirmed that the sealed lead-acid battery of the present invention can improve the rapid charge / discharge cycle life.

According to the test, it was found that the optimum range of the content of crystalline lead sulfate was 20 wt% to 40 wt%.

In the above examples, the negative electrode active material layer is manufactured to have a two-layer structure of an inner layer and a surface layer so that the crystalline lead sulfate is present more inside than the surface portion of the negative electrode active material layer. The crystalline lead sulfate-free paste is first filled into the lattice to a predetermined position, and then the crystalline lead sulfate-containing paste is filled or the crystalline lead sulfate particles are dispersed.
A paste containing no crystalline lead sulfate may be refilled thereon to form an active material layer containing crystalline lead sulfate therein. In any case, the method of allowing the crystalline lead sulfate to exist inside the negative electrode active material layer is arbitrary.

[Effects of the Invention] As described above, according to the present invention, the crystalline lead sulfate, which is difficult to reduce, is allowed to exist inside the surface of the negative electrode active material layer of the negative electrode plate. The charge overvoltage during charging can be kept low for a long period of time without affecting the discharge capacity. As a result, the generation of hydrogen gas from the negative electrode plate can be suppressed, the charging efficiency can be improved, and the rapid charge / discharge cycle can be achieved. The life can be greatly extended.

When the negative electrode active material layer has a two-layer structure including an inner layer containing crystalline lead sulfate and a surface layer not containing crystalline lead sulfate, the negative electrode active material layer can be reliably and controllably loaded with crystalline lead sulfate. Can be present.

[Brief description of drawings]

FIG. 1 is a diagram showing the results of rapid charge / discharge cycle life test of the sealed lead acid battery of the embodiment of the present invention and the conventional sealed lead acid battery, and FIG. 2 is the sealed lead acid battery of the embodiment of the present invention. It is a diagram which shows the charging characteristic at the time of rapid charging with the conventional sealed lead acid battery.

Continuation of the front page (56) References JP-A-58-123657 (JP, A) JP-A-58-169870 (JP, A) JP-A-62-150658 (JP, A)

Claims (2)

[Claims] 1. A sealed lead-acid battery using a negative electrode plate in which a refractory crystalline lead sulfate is present inside the negative electrode active material layer rather than on the surface thereof. 2. The sealed lead acid battery according to claim 1, wherein the negative electrode active material layer includes an inner layer containing the crystalline lead sulfate and a surface layer containing no crystalline lead sulfate.