JPH05343068A - Plate for lead acid battery - Google Patents

Abstract

PURPOSE:To heighten porosity with a small quantity of pore creating particulates. CONSTITUTION:A hollow particulate which expands when it is heated and contracts when heating is stopped, is added to an active material as a pore creating particulate. In a plate ageing process, a plate is heated, and the pore creating particulate is expanded. When the heating is stopped, the pore creating particulate contracts, and a void is created in the active material by a pore creating particulate contracting quantity, so that electrolyte can be held in this void.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead storage battery electrode plate in which fine pore-forming particles are added to an active material.

[0002]

2. Description of the Related Art Generally, it has been known that the capacity of a lead storage battery can be increased if the amount of an electrolytic solution (sulfuric acid) penetrating into an active material can be increased. Therefore, it has been proposed to increase the porosity of the active material by adding porous fine pore-forming particles to the active material. For example, Japanese Patent Laid-Open No. 1-1348
In the lead-acid battery electrode plate disclosed in Japanese Patent Laid-Open No. 65, the hollow porous fine particles containing SiO ₂ as a main component are added as pore forming fine particles to the positive electrode active material. This hollow porous fine particle has a large number of fine pores on the wall surface of the particle, and the amount of sulfuric acid retained in the positive electrode plate is increased by sucking sulfuric acid into the hollow portion inside the particle.

[0003]

When such hollow porous fine particles are added to the active material, the amount of the electrolyte solution retained in the active material can be increased, but the hollow porous particles that can be added to the active material are added. There is a limit to the amount of fine particles. This is because as the amount of the hollow porous fine particles added increases, the electronic coupling between the active material particles is impaired and the capacity of the lead storage battery decreases. By the way, in the electrode plate disclosed in the above publication,
The amount of the hollow porous fine particles added is limited to 10% by weight based on the positive electrode active material after chemical conversion.

Since there is a limit to the amount of addition of hollow porous fine particles, the number of fine holes provided in the hollow porous fine particles is increased and then the diameter of the fine pores is increased so that the hollow porous fine particles are present on the wall surface of the hollow porous fine particles. It was investigated to increase the specific surface area of the pores with respect to the surface area of the hollow porous fine particles by increasing the volume of the fine pores or by decreasing the diameter of the fine pores but increasing the number of the fine pores of the hollow porous fine particles.

However, increasing the specific surface area of the pores with respect to the surface area of the hollow porous fine particles causes a problem that the wall strength of the hollow porous fine particles is reduced. Further, when the volume of the pores is increased as in the former case, there is a problem that the active material enters the pores and the pores are blocked by the active material. Further, in the latter case where the diameter of the pores is small, there arises a problem that the rate at which the sulfuric acid retained in the hollow is supplied to the active material through the pores becomes slow. As described above, in the conventional lead-acid battery electrode plate in which the hollow porous fine particles are added to the active material, there is a limit in increasing the porosity of the active material, and even if sulfuric acid is retained by the hollow porous fine particles, it is retained. Sulfuric acid cannot penetrate into the active material sufficiently,
The capacity of the lead storage battery could not be increased sufficiently.

An object of the present invention is to provide an electrode plate for a lead storage battery, which is capable of sufficiently permeating sulfuric acid into an active material and increasing the initial capacity and the high rate discharge characteristic capacity of the lead storage battery.

[0007]

DISCLOSURE OF THE INVENTION The present invention is intended for a lead storage battery electrode plate in which fine particles for pore formation are added to an active material, and is a hollow that expands when heated and contracts when heating is stopped. The fine particles are used as fine particles for pore formation.

[0008]

When hollow fine particles that expand when heated and contract when heating is stopped are used as the fine particles for pore formation as in the present invention, the unformed electrode plate is subjected to heat treatment in the aging step of the active material. Expand the fine pore-forming particles in the active material paste, and after the active material paste has dried to a certain degree and becomes self-supporting, the heat treatment is stopped to shrink the fine pore-forming particles, and the fine particles expand. It is possible to form pores in the active material having a diameter substantially equal to the diameter of the fine pore-forming particles. Shrinking fine particles remain in the holes, but since the fine particles are in a shrunk state, a sufficient volume can be secured in the formed holes. Therefore, according to the present invention, it is possible to increase the porosity of the active material by using a relatively small amount of fine particles for pore formation with respect to the active material, and without impairing the electronic bonding between the active material particles as in the conventional case. In addition, the porosity of the active material can be increased. Moreover, since the sulfuric acid is not retained inside the pore-forming fine particles, there is no problem that the retained sulfuric acid becomes difficult to permeate into the active material unlike the conventional electrode plate.

[0009]

EXAMPLES Examples of the present invention will be described in detail below. The lead-acid battery plate of this example was manufactured as follows. First, dilute sulfuric acid and lead or lead oxide powder and hollow fine particles with a particle size of 15 μm, which expand when heated above a predetermined temperature and expand when heating is stopped and shrink when temperature falls, are kneaded to form a positive electrode active material paste. Had made. In this example, plastic hollow fine particles sold by Nippon Filter Co., Ltd. under the name of Expancel (trade name) were used. The hollow fine particles have an average particle diameter of 15 μm, and the thermal expansion starts at about 90 ° C. and the volume becomes 60 times at maximum. The amount of the hollow fine particles added to the active material paste is an amount that can increase the porosity of the active material and does not significantly reduce the strength of the active material. On the other hand, it is preferably 5 to 15% by weight. The hollow fine particles are expanded in the aging process of the active material paste. In the usual aging step, the temperature of the active material paste in the electrode plate rises to around 40 ° C. Therefore, when the above-mentioned hollow fine particles are used, the active material paste is heated to 90 ° C. or higher by using a heating means such as a heater before the active material paste dries to exhibit self-supporting property (or lose viscosity). To heat. Then, the active material paste is dried while maintaining the thermally expanded state of the hollow fine particles, and after the active material paste exhibits the self-sustaining property, the heating is stopped to shrink the expanded hollow fine particles.

In order to investigate the characteristics of the lead-acid battery electrode plate of this example, five types of positive electrode plates a to e were prepared and tested. The positive electrode plates a and b are the electrode plates of the present embodiment made by adding 5% by weight and 10% by weight of hollow fine particles to the positive electrode active material paste. The positive electrode plates c and d are conventional electrode plates made by adding hollow porous fine particles (SiO particles) that do not change in volume due to heat to the positive electrode active material paste in an amount of 5% by weight and 10% by weight, respectively. The positive electrode plate e is a conventional electrode plate to which fine particles for pore formation are not added. It should be noted that each of the positive electrode plates a to e has the same structure except for the structure of the fine particles for pore formation.

For each electrode plate, 40 g of the active material paste was applied to a current collector (50 × 100 × 50) made of a lead grid and the paste-filled electrode plate was aged as follows and then formed under the same conditions. Manufactured. For aging, the temperature is 45 ° C and the humidity is 98%.
The paste electrode plate was left for 60 hours in the aging tank in the above atmosphere to semi-dry the active material paste of the paste-filled electrode plate. Next, the temperature in the aging tank was raised to 90 ° C. and the paste-filled electrode plate was left for 0.5 hour to expand the hollow fine particles contained in the active material paste. Next, the temperature in the aging tank was gradually lowered to shrink the hollow fine particles in the paste-filled electrode plate. At the time of contraction of the hollow fine particles, the active material paste of the paste electrode plate is almost in a dried state, and voids are formed in the parts where the hollow fine particles in the active material contract.

Lead acid batteries A to E were made by combining the positive electrode plates a to e thus produced with negative electrode plates having the same characteristics, and the lead acid batteries A to E were repeatedly charged and discharged. Then, in the 5th cycle, the lead-acid batteries A to E are respectively set to 1A and 5A.
The lead storage batteries A to E were discharged to measure the discharge duration. Table 1 shows the measurement results.

[0013]

[Table 1] From this table, lead acid batteries A and B using the electrodes a and b of this example
In comparison with the lead storage batteries C to E using the conventional electrode plates c to e, the discharge duration is longer, and the initial capacity and the high rate discharge characteristic capacity are higher. It can be seen that the discharge duration of the battery becomes longer especially when the amount of the hollow fine particles added is large. It is considered that this is because the porosity of the active material increases and the electrolytic solution (sulfuric acid) permeates deep into the active material by adding the hollow fine particles to the active material.

Next, lead storage batteries F and G were prepared using electrode plates f and g prepared by adding 15% by weight and 20% by weight of hollow fine particles to the positive electrode active material paste, respectively. Charge and discharge were repeated for each of the lead storage batteries A, B, and E described above and G. Then, the capacity ratio of each lead acid battery was measured to examine the charge / discharge characteristics of each battery. FIG. 1 shows the measurement result. From this figure, it can be seen that the charge / discharge characteristics deteriorate when the amount of the hollow fine particles added exceeds a certain value. From this result, it is understood that the amount of the hollow fine particles added is preferably 15% by weight or less based on the active material paste.

In the above examples, the hollow fine particles that started thermal expansion at 90 ° C. or higher were used, but if the hollow fine particles that thermally expand at the normal aging temperature (about 40 ° C.) are used, the aging process will be performed. There is an advantage that it is not necessary to perform special heating in.

[0016]

According to the present invention, since the hollow fine particles that expand when heated and contract when heating is stopped are used as the fine pore-forming particles, pores having a diameter substantially equal to the diameter of the expanded fine pore-forming particles are formed. It can be formed in the active material. Therefore, according to the present invention, it is possible to increase the porosity of the active material without impairing the electronic coupling between the active material particles as in the conventional case. Moreover, since the sulfuric acid is not retained inside the pore-forming fine particles, there is no problem that the retained sulfuric acid becomes difficult to permeate into the active material unlike the conventional electrode plate. Therefore, a lead storage battery having a high capacity can be obtained by using the electrode plate of the present invention.

[Brief description of drawings]

FIG. 1 is a diagram showing charge / discharge characteristics of a lead storage battery used in a test.

Claims (1)

[Claims] 1. An electrode plate for a lead storage battery, wherein a pore-forming fine particle is added to an active material, wherein the pore-forming fine particle is hollow fine particle which expands when heated and contracts when heating is stopped. An electrode plate for a lead storage battery, which is characterized in that