JPH0620676A - Sealed secondary battery - Google Patents

Abstract

PURPOSE:To provide a sealed secondary battery capable of improving charge/ discharge cycle life. CONSTITUTION:Of electrode groups horizontally arranged in a plurality of layers, a fine porous film separator 4 is used for the upper electrode group, and a film separator 3 for the lower electrode group. Since the electrode group using the film separator is used in the lower part of a battery jar, and the electrode group using the fine porous film separator is used in the battery jar upper part, thus, it can be arrested by a free electrolyte 9 that dendrite is grown in the electrode group in the battery jar lower part, resulting in an internal short-circuit, and the oxygen generated from the positive electrode in the electrode group on the battery jar upper part can be efficiently absorbed by the negative electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed secondary battery, and more particularly to a separator for each pole group in a sealed secondary battery in which pole groups are arranged horizontally.

[0002]

2. Description of the Related Art Sealed secondary batteries are used for portability and stationary because they are easy to maintain.
It is known that if the electrolytic solution held in the pole group is unevenly distributed in the height direction, it becomes difficult for gas to be absorbed in the lower part of the pole group, so that the capacity per floor area is limited.

That is, in order to guide oxygen generated from the positive electrode at the end of charging or during overcharging to the negative electrode through the separator and the liquid-retaining layer to be absorbed by the negative electrode, it is necessary to limit the electrolytic solution held in the electrode group. The reason is that when the height of the pole group is increased to increase the capacity per floor area, the electrolytic solution is likely to be unevenly distributed in the height direction.

As described above, when the electrolytic solution is unevenly distributed, oxygen generated in the lower part of the electrode group stays in the electrode group, the internal pressure of the battery rises, and leakage occurs, or the current density in the lower part of the electrode group becomes high. As a result, the metal crystals of the negative electrode are deposited in the form of dendrites during charging, causing an internal short circuit, which has been a factor in shortening the battery charge / discharge cycle life.

Such a problem can be solved in a battery composed of a single pole group by arranging the pole group horizontally, but in a battery composed of a plurality of pole groups,
Even if the pole groups were arranged horizontally, it was difficult to eliminate them.

[0006]

The above-mentioned conventional sealed secondary battery has not been able to solve the problem that the charge / discharge cycle life becomes short due to uneven distribution of the electrolyte.

[0007]

In order to solve the above-mentioned problems, the present invention provides a hermetically sealed structure in which an electrolytic solution is held in a pole group consisting of a negative electrode, a positive electrode, and a separator and a liquid retaining layer interposed between the positive and negative electrodes. In the secondary battery of the type, the electrode group is arranged in a plurality of layers in a horizontal direction, and a microporous membrane separator is used for the upper electrode group and a membrane separator is used for the lower electrode group.

[0008]

[Operation] Therefore, in the present invention, among the electrode groups arranged in a plurality of layers in the horizontal direction, a microporous membrane separator is used for the upper electrode group and a membrane separator is used for the lower electrode group, so that there is no free electrolyte solution. In the upper electrode group, oxygen generated from the positive electrode can be efficiently absorbed in the negative electrode by the microporous membrane separator, and in the lower electrode group where free electrolyte is present, the negative electrode metal crystals are deposited in dendrite form by the membrane separator. It is possible to suppress an internal short circuit.

[0009]

EXAMPLE FIG. 1 is a sectional view of a nickel-zinc storage battery as a sealed secondary battery of the present invention.

In FIG. 1, 1 is a negative electrode plate containing metallic zinc and zinc oxide as main components, 2 is a positive electrode plate containing nickel hydroxide as a main component, and between the negative electrode plate 1 and the positive electrode plate 2. , A membrane separator 3 comprising a microporous film and a cellophane membrane or a microporous membrane separator 4 comprising two microporous films
And the liquid-retaining layer 5 made of nylon nonwoven fabric or polypropylene nonwoven fabric or the like to form the pole group.

Then, of the pole group, the membrane separator 3
A group of electrodes using the above is stored in the lower part of the battery case 6, and a group of electrodes using the microporous membrane separator 4 is stored in the upper part of the battery case 6, and potassium hydroxide having a specific gravity of 1.35 is added with lithium hydroxide as an electrolytic solution. The aqueous solution was injected up to 80 to 95% of the theoretical value of all the voids in the pole group and sealed to obtain the battery of the present invention. In FIG. 1, 7 is a negative electrode terminal and 8 is a positive electrode terminal.

In the battery of the present invention thus manufactured, the free electrolytic solution 9 is generated in the lower part of the battery case 6.
Is set so that it exists near the electrode group using the membrane separator 3 and below the electrode group using the microporous membrane separator 4, and if necessary, the electrode group using the membrane separator 3 It is also possible to change the composition ratio of the electrode group using the microporous membrane separator 4.

The above-mentioned battery A of the present invention has a capacity of 100 Ah.
However, Comparative Battery B using a membrane separator 3 composed of a microporous film and a cellophane membrane for all polar groups, and a microporous membrane separator 4 composed of a microporous film for all polar groups
Comparative battery C using was prepared and the following tests were conducted.

FIG. 2 shows the results of charge and discharge cycle life tests performed on the battery A of the present invention and the comparative batteries B and C. The conditions of this charge / discharge cycle life test are
After being charged with a current of 0.1 C for 10.5 hours, it was discharged to 1.2 V / cell at a current of 0.5 C in an atmosphere of 25 ° C.

From FIG. 2, it can be seen that the comparative battery B has about 120 cycles and the comparative battery C has about 50 cycles, and the discharge capacity has decreased to 60% of the initial capacity to reach the end of its life, while the invention battery A has 180 cycles. It was found that the discharge capacity did not decrease until about a cycle. This means that since the comparative battery C uses the microporous membrane separator 4 made of a microporous film for all the electrode groups, crystals of metallic zinc grow in a dendrite form on the zinc negative electrode, which leads to an internal short circuit. On the other hand, it is clear from Comparative Battery B and Invention Battery A that such an internal short circuit did not occur.

FIG. 3 shows the result of measurement of the change in oxygen absorption efficiency during the charge / discharge cycle test by the change in battery weight.

From FIG. 3, it was found that the comparative battery B had a low oxygen absorption efficiency from the beginning of the charge / discharge cycle test, whereas the inventive battery A and the comparative battery C were good. This means that the comparative battery B cannot efficiently absorb oxygen generated from the nickel positive electrode with the zinc negative electrode because the membrane separator 3 including the microporous film and the cellophane film is used for all the electrode groups. On the other hand, the present invention battery A
It is clear from Comparative Battery B that it can efficiently absorb the oxygen.

[0018]

As described above, the battery of the present invention prevents an internal short circuit by the membrane separator even if the negative electrode metal grows in a dendrite shape at the time of charging due to the free electrolytic solution existing in the lower portion of the battery case. Oxygen generated from the positive electrode can be efficiently absorbed through the microporous membrane separator in the upper part of the battery case, improving the charge / discharge cycle life of a sealed secondary battery such as a nickel-zinc storage battery. Can be made.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a sealed secondary battery of the present invention.

FIG. 2 is a diagram showing the results of a charge / discharge cycle life test performed on the present battery A and the comparative batteries B and C.

FIG. 3 is a diagram showing changes in oxygen absorption efficiency by a negative electrode during a charge / discharge cycle life test of the present invention battery A and comparative batteries B and C.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Negative electrode plate 2 Positive electrode plate 3 Membrane separator 4 Microporous membrane separator 5 Liquid retaining layer 6 Battery case 7 Negative electrode terminal 8 Positive electrode terminal 9 Free electrolyte solution

Claims (1)

[Claims] 1. A sealed secondary battery in which an electrolytic solution is held in a pole group consisting of a negative electrode, a positive electrode, and a separator and a liquid retaining layer interposed between the positive and negative electrodes, wherein the pole group is a plurality of layers in the horizontal direction. A sealed secondary battery, which is arranged and uses a microporous membrane separator for the upper electrode group and a membrane separator for the lower electrode group.