JPH08180857A - Electrode plate for lead-acid battery - Google Patents

Abstract

PURPOSE: To provide an electrode plate for lead-acid battery in which the strength of an active material layer can be enhanced and the porosity of the active material layer surface part can be also increased. CONSTITUTION: To an active material layer, 5-10% by volume of a water-soluble binder (polyvinyl alcohol) 1 consisting of a water-soluble organic synthetic resin is dispersed. The polyvinyl alcohol 1 on the surface part of an electrode plate is eluted to an electrolyte by the formation of a battery, and the porosity of the electrode plate surface part is increased. The strength of the active material layer inner part is enhanced by the polyvinyl alcohol 1 left in the inner part of the electrode plate (not eluted to the electrolyte).

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.

[0002]

2. Description of the Related Art In order to increase the capacity of lead-acid batteries such as sealed lead-acid batteries, the mixing ratio of water and sulfuric acid in the active material paste is increased to increase the porosity of the surface of the active material layer and increase the porosity. It is known to increase the active material utilization rate of the board. However, when the mixing ratio of water and sulfuric acid increases, the viscosity of the active material paste decreases, and the active material paste is collected as a current collector (lattice).
Can no longer be filled. Therefore, there is a limit to increase the porosity of the active material by such a method. Therefore, it has been proposed to add a conductive material such as carbon to the active material to increase the utilization rate of the active material in the electrode plate. However, when a sealed lead-acid battery in which carbon is added to the active material is repeatedly charged and discharged by rapid charging, carbon is oxidized. In addition, when the density of the active material is low, the conductivity becomes low and charging becomes difficult. Therefore, there is a problem that the active material is miniaturized and the battery capacity is reduced. Therefore, it has been considered to add a fibrous substance such as polyflon as a binder to the active material so as to increase the strength of the active material and prevent the active material from falling off and suppressing miniaturization. However, since such a fibrous substance has water repellency, the wettability of the electrolytic solution with respect to the active material of the electrode plate is reduced, and the capacity of the battery is reduced. Therefore, as disclosed in JP-A-6-111813, it has been proposed to add a water-soluble pore forming agent composed of cellulose fibers to the active material layer. With this kind of plate,
During the formation of the battery, the electrolytic solution penetrates into the porous part on the surface of the electrode plate,
Cellulose fibers on the surface of the electrode plate are eluted into the electrolytic solution.
Therefore, the active material particles on the surface of the electrode plate are condensed with each other while forming a void in the portion where the cellulose fibers were present,
The volume of the porous portion on the surface of the electrode plate increases. Moreover, since the cellulosic fibers inside the electrode plate are gradually melted by the charge and discharge of the battery and the porosity inside the electrode plate is gradually increased, the charge and discharge reaction part of the battery is not locally concentrated. Therefore, when this type of electrode plate is used, the cycle life of the battery can be extended without reducing the capacity of the battery.

[0003]

However, even if cellulose fibers are added to the active material layer, the binding force between the active materials cannot be sufficiently increased, and there is a limit to increase the strength of the active material layer. there were.

An object of the present invention is to provide an electrode plate for a lead storage battery in which the strength of the active material layer can be increased and the porosity of the surface portion of the active material layer can be increased.

[0005]

According to the present invention, a water-soluble binder made of a water-soluble organic synthetic resin is dispersed in an active material layer.

As the water-soluble binder, polyvinyl alcohol is used, and the ratio of this polyvinyl alcohol to the active material in the active material layer is preferably 5 to 10% by volume. Since polyvinyl alcohol has a high degree of fresh water, it does not generate gas accumulation even in the fine pores inside the electrode plate.
Can supply sulfuric acid. Polyvinyl alcohol acts as a kind of surfactant. Since a normal surfactant is oxidized and decomposed on the positive electrode plate, it gradually disappears during charging and does not last for a long time. On the other hand, polyvinyl alcohol has an advantage that the duration of action is long. Also,
5% by volume of polyvinyl alcohol to active material
When it is below the range, the porosity of the active material cannot be sufficiently increased and the strength of the active material cannot be sufficiently increased. Further, when the ratio of polyvinyl alcohol to the active material exceeds 10% by volume, the conductivity within the active material layer decreases.

[0007]

When a water-soluble binder made of a water-soluble organic synthetic resin is dispersed in the active material layer as in the present invention, the electrolytic solution penetrates into the porous portion of the electrode plate surface during the formation of the battery, and The water-soluble binder on the plate surface elutes in the electrolytic solution. Therefore, a void is formed in the portion where the water-soluble binder was present, and the active material particles on the surface of the electrode plate are condensed with each other,
The volume of the porous portion on the surface of the electrode plate increases. In this way, the water-soluble organic synthetic resin on the surface of the electrode plate, which elutes in the electrolytic solution during the formation of the battery, serves as a pore-forming agent to increase the porosity of the surface of the electrode plate. In addition, since the organic synthetic resin has a strong binding force as a binder, the organic synthetic resin remaining inside the electrode plate (not eluted in the electrolytic solution) firmly binds the active material particles to each other to form the active material layer. Increase the internal strength. Therefore,
By using the electrode plate of the present invention, the capacity of the battery can be increased and the cycle life can be extended.

[0008]

Embodiments of the present invention applied to a positive electrode plate for a lead storage battery will be described in detail with reference to the drawings.

Example 1 The positive electrode plate of this example was manufactured as follows. First, a kneaded mixture of 74% by weight of lead monoxide (PbO), 11% by weight of lead, 5% by weight of dilute sulfuric acid having a specific gravity of 1.30 (20 ° C.) and 10% by weight of water has a polymerization degree of 500 (particle size: about 0.5 μm). 0.1% by weight of a water-soluble binder composed of polyvinyl alcohol (PVA) was added and further kneaded to prepare an active material paste. The amount of polyvinyl alcohol added is 10% by volume based on the active material in the active material layer after the active material layer is formed. The degree of polymerization of polyvinyl alcohol is preferably 1000 or less. When the degree of polymerization exceeds 1000, the solubility of polyvinyl alcohol decreases. Next, 150 g of this active material paste is filled in a current collector made of a lattice, and then ordinary aging and drying are carried out to complete the unformed positive electrode plate of this embodiment having an active material layer made of a paste type active material. did.

FIG. 1 shows the positive plate of this embodiment having a specific gravity of 1.05.
Immerse in dilute sulfuric acid (40 ℃) (20 ℃)
It is a figure which shows the schematic cross section after 40-hour chemical conversion with 0% of electricity. As shown in the figure, after the formation, since the polyvinyl alcohol 1 on the surface of the electrode plate is eluted into the electrolyte and the active material particles 2 on the surface of the electrode plate aggregate with each other, the porosity of the surface of the electrode plate is Will be significantly higher than. The polyvinyl alcohol 1 remaining inside the electrode plate binds the active material particles 2 to each other.

Example 2 The positive electrode plate of this example was manufactured by the same method as in Example 1 except that the amount of polyvinyl alcohol added to the active material was 5% by volume.

Example 3 The positive electrode plate of this example was manufactured by the same method as in Example 1 except that the amount of polyvinyl alcohol added to the active material was 12% by volume.

(Conventional Example) The positive electrode plate of this conventional example has the same structure as the positive electrode plate of this embodiment except that polyvinyl alcohol is not added to the active material paste.

Next, the positive electrode plate of Example 1 and the positive electrode plate of the conventional example were respectively combined with a known paste type negative electrode plate to make a battery of 2V-10Ah, and a test was conducted. Since the positive electrode plate has a smaller pore size than the negative electrode plate, gas accumulation is likely to occur. Therefore, the permeability of sulfuric acid is lowered, and the utilization rate of the active material is lowered. However, when the present invention is applied to the positive electrode plate, the active material utilization rate and the high rate discharge characteristics can be improved. FIG. 2 is a diagram showing the relationship between the pore size of the electrode plate of Example 1 and the electrode plate of the conventional example and the volume ratio of the pores having the pore size after the formation of the electrode plate. From this figure, it can be seen that the pore size of the electrode plate of Example 1 is larger than the pore size of the electrode plate of the conventional example. Then, each battery was discharged at 10 A, and the relationship between the discharge duration and the terminal voltage of each battery was examined. FIG. 3 shows the measurement result. From this figure, it can be seen that when the positive electrode plate of Example 1 is used, the discharge time of the battery becomes longer. This is because the positive electrode plate of Example 1 has a high porosity in the surface portion of the active material layer,
This is because diffusion of the electrolytic solution into the electrode plate is facilitated.

Next, 2.5 A (0.25 C) is applied to each of the above batteries.
After 2 hours of discharge, the battery was repeatedly charged at 1 A (0.1 C) for 6 hours to perform a charge-discharge cycle, and the cycle life characteristics of each battery were examined. FIG. 4 shows the measurement result. From this figure, it can be seen that the cycle life of the battery can be extended by setting the addition amount of polyvinyl alcohol to the active material to be 5 to 10% by volume. Table 1 is a diagram schematically showing a cross section of the electrode plate of each battery in every 100 cycles.

[0016]

[Table 1] From this table, it can be seen that the lead sulfate on the surface of the electrode plate increases (lead sulfate conversion progresses) as the charge and discharge cycle progresses for each electrode plate. In the conventional example, the porosity of the surface of the electrode plate is small,
It can be seen that lead sulfate proceeds so as to block the pores on the surface of the electrode plate in 0 cycle. As a result, in the conventional example, it becomes difficult for the electrolytic solution to be supplied to the inside of the electrode plate, and the capacity cannot be obtained. On the other hand, in the electrode plates of Examples 1 to 3, since polyvinyl alcohol gradually dissolves due to repeated charging / discharging of the battery, the charging / discharging reaction of the battery is not locally concentrated, and Reacts evenly, and lead sulphate on the surface is unlikely to occur. Even if the surface is converted to lead sulfate, the pores on the surface of the electrode plate are sufficiently large, so that the pores on the surface of the electrode plate are difficult to close. Moreover, since the polyvinyl alcohol remaining inside the electrode plate attracts sulfuric acid, the capacity of the battery does not easily decrease. However, when the amount of polyvinyl alcohol added is large, the electron conductivity between the active material particles is hindered and the battery reaction is partially concentrated, which has the opposite effect.

The structure of some of the inventions described in the specification will be described below.

(1) A positive electrode plate for a lead storage battery, wherein a water-soluble binder made of a water-soluble organic synthetic resin is dispersed in an active material layer made of a paste type active material.

(2) As the water-soluble binder, polyvinyl alcohol having a degree of polymerization of 1000 or less is used, and the ratio of the polyvinyl alcohol to the active material in the active material layer is 5 to 10% by volume. The positive electrode plate for a lead storage battery according to (1).

(3) Lead monoxide, lead, dilute sulfuric acid, water, and a water-soluble binder made of polyvinyl alcohol having a degree of polymerization of 1000 or less are kneaded to fill the active material paste in a current collector made of a lattice. A method for producing a positive electrode plate for a lead storage battery, which comprises aging and drying to produce a lead acid battery electrode plate containing 5 to 10% by volume of polyvinyl alcohol with respect to an active material.

[0021]

According to the present invention, since a water-soluble binder made of a water-soluble organic synthetic resin is dispersed in the active material layer, the water-soluble organic compound on the surface of the electrode plate which is eluted into the electrolytic solution during formation of the battery. The synthetic resin plays the role of a pore-forming agent and increases the porosity of the surface portion of the electrode plate. Then, the strength of the inside of the active material layer is increased by the organic synthetic resin remaining inside the electrode plate (not eluted in the electrolytic solution). Therefore, by using the electrode plate of the present invention, the capacity of the battery can be increased and the cycle life can be extended.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view after formation of an electrode plate of this embodiment.

FIG. 2 is a diagram showing the relationship between the pore size and the volume of the pores having the pore size after the electrode plate formation of the electrode plate used in the test.

FIG. 3 is a diagram showing the relationship between the discharge duration and the terminal voltage of the battery used in the test.

FIG. 4 is a diagram showing cycle life characteristics of a battery used in a test.

[Explanation of symbols]

 1 polyvinyl alcohol 2 active material particles

Claims (2)

[Claims] 1. An electrode plate for a lead storage battery, wherein a water-soluble binder made of a water-soluble organic synthetic resin is dispersed in the active material layer. 2. The lead according to claim 1, wherein polyvinyl alcohol is used as the water-soluble binder, and the ratio of the polyvinyl alcohol to the active material in the active material layer is 5 to 10% by volume. An electrode plate for storage batteries.