JPH10188989A - Negative electrode for lead-acid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the quantity of sodium lignosulfate in a negative electrode active material so as to lower unsatisfactory filling to improve the charging acceptability, and to reduce the calorific power to prevent the lowering of low-temperature high efficiency discharge capacity by adding sodium lignosulfate to a negative electrode plate for lead-acid battery restraining the flocculation of lead during the charging to refine lead particles, and adding a specified quantity of phosphoric acid or boric acid thereto. SOLUTION: A negative electrode active material paste formed by adding an addition agent such as sodium lignosulfonate and sulfuric acid to lead powder composed mainly of lead oxide, is filled in a collector, and aged, dried, and formed to obtain a negative electrode plate for lead-acid battery. At this stage, phosphoric acid or boric acid at 0.01-0.1wt.% (vs. lead powder) is added to the negative electrode active material. With this composition, the quantity of sodium lignosulfonate as a surfactant is reduced, and the paste is hardened to lower the imperfect filling and to improve the conductivity of an electrode plate and the charge acceptability is thereby improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cathode plate for a lead storage battery.

[0002]

2. Description of the Related Art In general, a cathode active material paste for a lead-acid battery is prepared by adding additives such as barium sulfate, carbon, and sodium ligninsulfonate to lead powder mainly composed of lead oxide.
It is manufactured by kneading with sulfuric acid and water. After filling this into a current collector, it is aged, dried and chemically formed to form an electrode plate. The low-temperature high-rate discharge capacity of the lead-acid battery cathode plate mainly depends on the specific surface area of the active material, and it is known that sodium ligninsulfonate functions to refine lead particles. Sodium ligninsulfonate is characterized by being easily adsorbed by lead and lead monoxide, but hardly adsorbed by lead sulfate. For this reason, in the early stage of chemical formation, if the electrolyte solution of sulfuric acid reacts with the unactivated active material containing lead monoxide as a main component to become lead sulfate, it cannot be adsorbed and elutes into the electrolyte solution. For this reason, Japanese Patent Publication No. 60-436
As disclosed in Japanese Patent Publication No. 26, a method has been proposed in which a paste with a large amount of addition is applied to this portion in order to secure the amount of sodium ligninsulfonate on the surface of the electrode plate in contact with the electrolytic solution and improve the performance. .

[0003]

However, when the amount of sodium ligninsulfonate is increased, the paste becomes softer due to the action as a surfactant, and the paste falls down from the current collector after filling into the current collector (hole). Autumn)
Occurs. In addition, when two layers are used, there is a problem that the number of steps is large and it takes time and effort. Further, when the amount of sodium ligninsulfonate, which is an organic polymer having poor conductivity, is increased, there arises a problem that charging becomes difficult (charging acceptability deteriorates).

[0004] It is an object of the present invention to reduce the amount of sodium ligninsulfonate in the cathode active material, thereby reducing the above-mentioned poor filling, improving the charge acceptability, and increasing the low temperature due to the reduced amount. An object of the present invention is to provide a cathode plate for a lead storage battery that does not cause a reduction in the rate discharge capacity.

[0005]

In order to solve the above-mentioned problems, the present invention relates to an active material paste containing lead oxide as a main component, containing 0.01 to 0.1 wt% of phosphoric acid or boric acid (vs. lead powder). ) Is added.

According to the present invention, by reducing the amount of sodium ligninsulfonate, which is a surfactant, the paste becomes hard, so that poor filling can be reduced. In addition, since sodium ligninsulfonate is an organic polymer having poor conductivity, by reducing the amount thereof, the conductivity of the electrode plate is also improved. Therefore, charge acceptability is also improved. Further, phosphoric acid or boric acid added to the cathode plate as an additive has a small reaction area with sulfuric acid because it coordinates with an unformed active material containing lead monoxide as a main component. For this reason, the amount of sodium ligninsulfonate desorbed by lead sulfate is reduced. Further, since the reaction area for the conversion to lead sulfate is small, the calorific value accompanying the reaction is also small. Therefore, the temperature rise of the electrolyte is also small. Here, since the solubility of sodium ligninsulfonate becomes smaller as the temperature becomes lower, the amount of sodium ligninsulfonate dissolved in the electrolyte during the conversion to lead sulfate is suppressed and the amount is secured. Therefore, a decrease in the low-temperature high-rate discharge capacity is not caused.

[0007]

The following is a description of the preferred embodiments. Example 1 The phosphoric acid used in Example 1 is a special grade reagent manufactured by Wako Pure Chemical Industries, Ltd. A mixture of lead powder mainly composed of lead monoxide, a predetermined amount of barium sulfate, carbon, and 0.2 wt% of sodium ligninsulfonate based on the lead powder is added to a mixture of 0.1 wt.
A solution of 025% phosphoric acid in ion-exchanged water and sulfuric acid were added and kneaded to form an active material paste. Next, after these active material pastes were filled in a current collector, aging (50 ° C., RH 95%, 18 h) and drying (50 ° C., 16
h) to produce an unformed cathode plate. One cathode plate, two anode plates, and a separator were laminated, respectively, to form an electrode plate group, and these were inserted into a vinyl chloride container under a constant pressure. A predetermined amount of sulfuric acid was injected therein, and the battery was formed to form a lead storage battery A.

Example 2 A 0.1% aqueous solution was prepared using the phosphoric acid of Example 1.
An aqueous solution of a cathode plate (sodium ligninsulfonate: 0.2 wt%) to which no phosphoric acid was added was added to the aqueous solution for 1 hour.
Immersion (room temperature, normal pressure), 0.025% phosphoric acid on the surface of the electrode plate
The electrode plate was prepared as follows. Then, a lead storage battery B was produced in the same procedure as in Example 1.

Conventional Example 1 Powder obtained by adding the same amount of barium sulfate, carbon, and 0.4 wt% sodium lignin sulfonate to lead powder to lead powder mainly composed of lead monoxide, A paste was prepared by kneading ion-exchanged water and sulfuric acid. That,
A lead storage battery C was manufactured according to the same procedure as that of the first embodiment.

Conventional Example 2 Further, a paste containing 1.0 wt% of sodium ligninsulfonate was prepared. The current collector was filled with only 0.2 wt% paste, and then the paste was overlapped on both surfaces to form a filled electrode plate. Then, a lead storage battery D was manufactured in the same procedure as in Example 1.

When the filling properties of the various pastes of these batteries were filled in a grid, the percentage of rejection was measured when the paste was dripped from the grid.
The paste properties at this time are a water content of 10% and a lead sulfate content of 16%. Next, the charge acceptability of these batteries was measured. In this test method, first discharge half of the battery capacity at 25 ° C, leave the battery in that state at 0 ° C for 18 hours, and then charge it at 0 ° C at a constant voltage of 2.4 V and measure the amount of charge for 10 minutes Is the way. The specific surface area of the active material was measured as a value corresponding to the remaining amount of sodium ligninsulfonate after the formation of these four batteries was completed. Next, as a capacity test, a low rate (1.4 A) discharge capacity at normal temperature (25 ° C.) and a high rate (37.5 A) discharge capacity at low temperature (−15 ° C.) were measured. Further, these batteries were repeatedly charged / discharged according to the JIS light load test, and the number of times was measured. Table 1 shows the results. In this table, A1: Example 1, A
2: Example 2, B1: Conventional example 1, B1: Conventional example 2

[0012]

[Table 1]

[0013]

[Table 2]

First, when comparing the defective rate at the time of filling, the pastes of Examples 1 and 2 in which the amount of sodium ligninsulfonate was reduced could significantly reduce the defective rate as compared with Conventional Example 1 in which the added amount was doubled. You can see that it is. Conventional example 2 in which the paste was applied to both sides with the amount added five times that of the example,
It can be seen that the defect rate is orders of magnitude higher than others. From this result, it can be seen that the defective rate can be reduced by reducing the amount of sodium ligninsulfonate added.

Next, when comparing the charge acceptability, it can be seen that in Examples 1 and 2 in which the amount of sodium ligninsulfonate was reduced, the amount of electricity was increased by 1.5 times as compared with Conventional Example 1, and charging became easier. The reason why the amount of electricity charged in Conventional Example 2 is not different from that in the embodiment is considered to be that the paste near the current collector uses 0.2 wt%.

From the results of the capacity test, Examples 1 and 2, which are phosphoric acid-added products, are equivalent to Conventional Example 1 in which sodium ligninsulfonate is added twice, and Conventional Example 2 in which a paste in which sodium ligninsulfonate is added five times is applied to both sides It is. This is because the addition of phosphoric acid suppressed the elution of sodium ligninsulfonate and increased the specific surface area of the active material. In addition, the number of times of charge and discharge of the phosphoric acid-added product is almost the same as that of the increased product, and the same as the life performance. Therefore, from these results, it is understood that the batteries to which phosphoric acid is added are equivalent in performance, and have good filling properties and charge acceptability.

Next, an electrode plate manufactured by changing the addition amount of phosphoric acid used in the embodiment by the addition method of the embodiment 1 was used to fabricate a battery in the same procedure as described above, and the low temperature (−15 ° C.) FIG. 1 shows the results of the high-rate discharge test performed in step (1). from this result,
It can be seen that the effect is obtained in the range of 0.01% or more to 0.1% or more. It is also found that when the amount exceeds 0.1%, the capacity decreases. This is presumably because, when the amount of phosphoric acid added is too large, the coordination layer inhibits diffusion of the electrolytic solution or becomes a resistance, resulting in a decrease in capacity. Conversely, if the addition amount is 0.01% or less, it is considered that no effect is exhibited because a coordination layer cannot be formed.

Next, a similar experiment was conducted using the phosphoric acid addition method (immersion method) used in Example 2. As a result, almost the same results as in this example were obtained. In addition, as a result of performing the same experiment for boric acid, almost the same result as in this example was obtained.

[0019]

According to the present invention, by reducing the amount of sodium ligninsulfonate, which is a surfactant, the paste becomes hard, so that poor filling can be reduced. In addition, since sodium ligninsulfonate is an organic polymer having poor conductivity, by reducing the amount thereof, the conductivity of the electrode plate is also improved. Therefore, charge acceptability is also improved. Further, phosphoric acid or boric acid added to the cathode plate as an additive has a small reaction area with sulfuric acid because it coordinates with an unformed active material containing lead monoxide as a main component. Therefore, the amount of sodium ligninsulfonate desorbed by lead sulfate is reduced. Further, since the reaction area for conversion to lead sulfate is small, the calorific value accompanying the reaction is also small. Therefore, the temperature rise of the electrolyte is also small. Here, since the solubility of sodium ligninsulfonate becomes smaller as the temperature becomes lower, the amount of sodium ligninsulfonate dissolved in the electrolyte during the conversion to lead sulfate is suppressed and the amount is secured. Therefore, a decrease in the low-temperature high-rate discharge capacity is not caused.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the amount of phosphoric acid added to an electrode plate and a high rate (37.5 A) discharge capacity at low temperature (−15 ° C.) in a lead-acid battery using a cathode plate obtained according to the present invention.

Claims (1)

[Claims] 1. A lead battery cathode plate to which sodium ligninsulfonate having the function of suppressing the aggregation of lead during charging and making the lead particles finer is provided with phosphoric acid or boric acid.
A cathode plate for a lead-acid battery, characterized by adding 0.01 to 0.1 wt% (vs. lead powder).