JP2009070668A - Method of manufacturing positive electrode plate for control valve type lead-acid storage battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control valve type lead acid storage battery, wherein a thin and large electrode plate hard to deflect can be manufactured, large capacitance is ensured and drop in capacitance at an early stage is prevented. <P>SOLUTION: In the manufacturing method of a positive electrode plate for a control valve type lead acid storage battery, a base plate of lead alloy whose main component is lead is filled with a paste-like active material, for digestion/drying thereafter. The paste-like active material is added with graphite by 0.3-0.95 wt.% based on lead powder during digestion/drying, and quadribasic sulfate is generated by 75-95 wt.%. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a positive electrode plate for a control valve type lead-acid battery that has improved capacity and process flow.

A control valve type lead-acid battery is composed of a positive electrode plate and a negative electrode plate, which are filled with an active material paste on a substrate, alternately stacked via a mat-like separator mainly composed of fine glass fibers, By connecting the ears of the electrode plate by welding to form an electrode plate group, the electrode plate group is housed in a battery case, and a lid having an opening for pouring and exhausting is adhered to the battery case with welding or an adhesive. It is manufactured by injecting the electrolyte solution from the opening into the battery case so that the amount of the electrolyte is impregnated into the electrode plate group, and covering the rubber valve (control valve) over the opening for injection or exhaust. .

In recent years, valve-regulated lead-acid batteries have been used in various fields including backup power supplies for communication, electric power, disaster prevention, and power storage. These control valve type lead-acid batteries are required to have long life performance exceeding 10 years, volumetric energy density, improvement of utilization rate, and the like.

In order to improve the volumetric energy density and utilization rate, a porous material (eg, graphite) is added to the active material to increase the porosity in the active material, or the electrode plate thickness is reduced to increase the number of electrode plate groups. There is a known method of increasing the utilization rate of positive and negative electrode active materials by increasing the number of sheets. However, when graphite is added, the active material is peeled off from the lead alloy substrate due to the volume change of the active material, and the adhesiveness deteriorates and the capacity decreases. There was a problem of decreasing.

Therefore, as one of the methods for extending the life and improving the utilization rate of sealed lead-acid batteries, a paste-like active material containing lead powder, carbon powder, dilute sulfuric acid, water, and resin fibers is prepared, and the paste-like active material is After being applied to a lead alloy current collector, a positive electrode plate having an active material layer containing 50 to 70% by mass of tetrabasic lead sulfate is prepared by aging and drying, and the positive electrode plate is formed and sealed. In the manufacturing method of a lead-acid battery, it is known to contain 1.0-3.0 mass% carbon powder with respect to the said lead powder (patent document 1).

JP 2001-229920 A

In the method described in Patent Document 1, a positive electrode plate having an active material layer containing 50 to 70% by mass of tetrabasic lead sulfate is prepared, and 1.0 to 3.0% by mass of carbon powder is added to the lead powder. By containing, the life of the sealed lead-acid battery is extended, and the utilization rate of the active material is improved by containing carbon powder.
However, the electrode plate obtained by the method described in Patent Document 1 has a disadvantage that the electrode plate bends during the process flow, the electrode plate falls from the suspension base, and does not adsorb to the adsorption part of the transfer robot. The current situation is that the electrode plate has a certain thickness and is given strength.
Although this phenomenon depends on the thickness of the substrate, when the thickness is about 1 to 3 mm, the phenomenon becomes prominent when a large plate grid having a length of 300 mm or more is used.
Also, depending on the amount of graphite added, the substrate-active material adhesion enhancement effect due to the expansion of the graphite may be greater than the substrate-active material adhesion enhancement effect due to tetrabasic lead sulfate, leading to early capacity reduction. confirmed.
Therefore, the present inventors have made various studies, and by making the amount of 4-basic lead sulfate produced and the amount of graphite added within a desired range, it is possible to produce an electrode plate that is difficult to bend, and with a high capacity. And it discovered that the electrode plate which is hard to raise | generate an early capacity | capacitance fall could be provided.

The present invention relates to a method for producing a positive electrode plate for a control valve type lead-acid battery in which a lead-alloy substrate containing lead as a main component is filled with a paste-like active material and then aged and dried. While adding 0.3 to 0.95 mass% of graphite to the amount of lead powder to the substance, 75 to 95 mass% of 4-basic lead sulfate is produced at the time of aging and drying.

In a positive electrode plate of a valve-regulated lead-acid battery, a base made of a lead alloy is filled with a paste in which 0.3 to 0.95% by mass of graphite is added to the amount of lead powder, and then in a ripening / drying process, 4-basic sulfuric acid By producing 75 to 95% by mass of lead, it has a high capacity and is difficult to bend even with a large electrode plate.

The control valve type lead-acid battery of the present invention adds 0.3 to 0.95 mass% of graphite to the amount of lead powder in the paste-like active material, and 75 to 95 mass of 4-basic lead sulfate during aging and drying. % Is a control valve type lead-acid battery that increases the capacity, prevents the bending of the electrode plate, improves the process fluidity, and does not easily cause an early capacity decrease.

In the present invention, after filling the large substrate with the positive electrode active material paste, the amount of tetrabasic lead sulfate produced in the aging / drying process is 75 to 95% by mass. This is because the flexural strength of the electrode plate is increased by the generation of the electrode plate, which leads to improvement of process flow and good adhesion between the positive electrode substrate and the active material. Tetrabasic lead sulfate, like tribasic lead sulfate, converts to lead dioxide as the reason for increasing the positive electrode plate strength and improving the adhesion between the substrate and active material of 4-basic lead sulfate. Since lead sulfate has a smaller volume expansion rate during chemical conversion than tribasic lead sulfate, the adhesion between the lattice and the active material is hardly impaired by chemical conversion. The adhesiveness between them is good.
However, an electrode plate with a production amount of 4-basic lead sulfate of less than 75% by mass has insufficient adhesion between the substrate and the active material or between the active materials. Cracks occur between the active materials, causing an early capacity drop. In addition, the electrode plate in which the production amount of tetrabasic lead sulfate exceeds 95% by mass includes at least about 5% of pure lead, lead monoxide, tribasic lead sulfate, etc. in the active material after aging and drying. Therefore, it is difficult to produce an electrode plate under any aging and drying conditions.
Furthermore, when the active material form in the electrode plate after aging and drying is mainly tribasic lead sulfate, the volumetric expansion coefficient of the tribasic lead sulfate itself is large, and in addition, the volume expansion of graphite results in the substrate-active Adhesion between materials and between active materials is impaired, resulting in an early capacity drop.
Therefore, the production amount of tetrabasic lead sulfate is preferably 75 to 95% by mass.

In addition, in the present invention, adding 0.3 to 0.95 mass% of graphite to the amount of lead powder in the paste-like active material increases the porosity in the active material and the reaction of the control valve type lead acid battery. This is because the diffusion of sulfuric acid, which is an electrolytic solution, is promoted, the utilization factor of the active material is increased, and the capacity of the control valve type lead storage battery is increased.
However, when the amount of graphite added is less than 0.3% by mass, the porosity in the active material does not change much compared to the case where graphite is not added, and the capacity is not increased. On the other hand, if the amount of graphite added exceeds 0.95% by mass, a large volume expansion causes a large crack in the active material, causing an early capacity drop.
Therefore, the addition amount of graphite in the positive electrode active material is preferably 0.3 to 0.95 mass%.

  In addition, the electrode plate group of the control valve type lead-acid battery is configured by alternately stacking positive and negative electrode plates with separators interposed between them, and usually has a configuration in which one negative electrode plate is provided by disposing negative electrode plates at both ends. ing. Along with the increase in the number of negative electrode plates, the positive electrode plates are inevitably thinned to increase the number of sheets.

After filling the positive electrode substrate of Ca-based lead alloy (dimensions 400 mm long × 150 mm wide × 2.1 mm thick) with an active material paste containing 0.5% by weight of graphite with respect to the amount of lead powder, aging and drying are performed. Thus, an unchemically formed positive electrode plate was obtained. Next, a plurality of unformed paste type positive electrode plates and a plurality of unformed paste type negative electrode plates produced by a known method are alternately laminated through a glass mat made of long glass fibers. And the same-polarity board of this laminated body was welded by the burner system, and the electrode group was obtained. Next, the required number of the electrode plate groups is inserted into a polypropylene battery case, a lid is heat sealed to the battery case, and a rare gravity of 1.21 (20 ° C.) is placed in the battery case from the liquid port of the lid. Sulfuric acid (electrolytic solution) was injected to such an extent that the electrode plate group was impregnated, and a battery case was formed under predetermined conditions to produce a 1300 Ah control valve type lead storage battery (Invention 1).
The aging / drying was carried out in an atmosphere at a temperature of 65 ° C. and a humidity of 95% for 24 hours, and then drying was carried out in an atmosphere at a temperature of 60 ° C. and a humidity of 10%.

A 1300 Ah controlled valve lead-acid battery was produced in the same manner as in Example 1 except that the aging temperature was set to 70 ° C. (Invention 2).

A 1300 Ah controlled valve lead-acid battery was produced in the same manner as in Example 1 except that the aging temperature was set to 80 ° C. (Invention 3).

(Comparative Example 1)
A 1300 Ah control valve lead-acid battery was produced in the same manner as in Example 1 except that the aging temperature was 40 ° C. (Invention 3).
(Comparative Example 2)
A 1300 Ah controlled valve lead-acid battery was produced in the same manner as in Example 1 except that the aging temperature was 50 ° C. (Invention 3).
In the present invention, the amount of tetrabasic lead sulfate produced was changed by changing the aging temperature. However, the humidity and time during aging may be changed, and the heat transfer rate varies depending on the thickness of the electrode plate. Therefore, the thickness of the electrode plate may be changed, and these may be changed as appropriate to control the amount of tetrabasic lead sulfate produced.
For example, it is well known that when the same substrate is used and the humidity and time during aging are the same, increasing the aging temperature can increase the amount of tetrabasic lead sulfate produced, and the substrate is thin. For thicker and thicker plates, the heat transfer rate of the thin plate is faster than that of the thick plate, so if the aging conditions (aging temperature, humidity, time) are the same, the amount of 4-basic lead sulfate produced can be increased. Is obvious.

About each obtained control valve type lead acid battery (Invention 1-3, Comparative Examples 1-2), the amount of 4-basic sulfuric acid, electrode board bending, process fluidity, and capacity reduction cycle number were investigated.
The amount of 4-basic lead sulfate was measured by the X-ray diffraction method for each positive electrode plate produced.
The electrode plate was fixed by using the center part in the longitudinal direction of one electrode plate as a fulcrum, and the displacement was measured by how much both sides bend due to its own weight.
The process fluidity is excellent when the substrate filled with the paste-like active material is placed on the suspension base, aged and dried, then dropped from the suspension base and can be gripped by the transfer robot well. ○). It was evaluated that the process fluidity was inferior (×) if the drop from the suspension base or the gripping failure by the robot was at least one out of 300. In addition, since the holding plate is inserted every several dozens of plates until the paste active material is filled and ripening / drying is completed, the plates are difficult to bend.
The capacity reduction cycle number indicates the cycle number when the capacity is reduced to 90% of the initial capacity. The cycle test conditions were a discharge current of 130 A (0.1 CA), a discharge to a final voltage of 1.8 V, and then a 110% charge with respect to the discharge capacity in the recovery charge. Up to 90% of the discharge capacity was constant current charged at 130 A (0.1 CA), and from 90% to 110% of the discharge capacity was constant current charged at 65 A (0.05 CA).

As shown in Table 1, the present invention 1 to 3 in which the amount of 4-basic lead sulfate in the electrode plate is 75% by mass or more has little electrode plate deflection displacement and is excellent in process fluidity. . Compared with it, it turns out that Comparative Examples 1-2 which made the production amount of 4-basic lead sulfate in an electrode plate less than 75 mass% has much electrode plate bending displacement, and is not suitable for process fluidity | liquidity.
Moreover, this invention 1-3 which made the production | generation amount of the 4-basic lead sulfate in an electrode plate 75 mass% or more has favorable adhesiveness between board | substrate-active materials or between active materials, and the number of capacity reduction cycles You can see that it is excellent. In comparison, Comparative Examples 1 and 2 in which the amount of 4-basic lead sulfate in the electrode plate is less than 75% by mass has insufficient adhesion between the substrate and the active material or between the active materials. Due to the volume expansion, cracks occurred between the substrate and the active material or between the active materials, causing an early capacity drop.

Next, the amount of graphite added to the active material paste is 0 to 1.0% by mass with respect to the amount of lead powder as shown in Table 2, the subsequent aging temperature is 70 ° C., and each positive electrode plate is produced. In the same manner as in Example 1, a 1300 Ah control valve type lead storage battery was manufactured (Invention 2, 4 to 5, Comparative Examples 3 to 6). At this time, the amount of 4-basic lead sulfate produced when the positive electrode was not formed was 85%.

With respect to each of the obtained control valve type lead-acid batteries (Invention 2, 4 to 5, Comparative Examples 3 to 6), the initial capacity ratio and the capacity reduction cycle number were examined.
The initial capacity ratio is the capacity ratio when the capacity of Example 2 is 100 when the capacity is discharged to a final voltage of 1.8 V with a discharge current of 130 A.
The capacity reduction cycle number indicates the cycle number when the capacity is reduced to 90% of the initial capacity. The cycle test conditions were a discharge current of 130 A (0.1 CA), and the battery was discharged to a final voltage of 1.8 V. Thereafter, in recovery charge, 110% charge was performed with respect to the discharge capacity. Up to 90% of the discharge capacity was constant current charged at 130 A (0.1 CA), and from 90% to 110% of the discharge capacity was constant current charged at 65 A (0.05 CA).

As shown in Table 2, the present inventions 2 and 4 to 5 are excellent in both initial capacity and capacity reduction cycle number by setting the amount of graphite added in the positive electrode active material to 0.3 to 0.95 mass%. It was. In contrast, Comparative Examples 3 to 4 do not add graphite in the positive electrode active material, or the addition amount is small, so that the porosity in the active material is hardly changed and the initial capacity is difficult to be obtained. The number of reduction cycles was excellent. In Comparative Examples 5 to 6, when the amount of graphite added exceeds 0.95 mass%, the initial capacity ratio is excellent, but the adhesion between the substrate and the active material or between the active materials is large due to large volume expansion. It was spoiled by generation | occurrence | production, the early capacity | capacitance fall was caused, and the capacity fall cycle number was inferior.

Claims (1)

  In a method of manufacturing a positive electrode plate for a control valve type lead storage battery, in which a paste alloy material containing lead as a main component is filled with a paste active material and then aged and dried, lead powder is added to the paste active material. A control valve type lead-acid battery positive electrode plate characterized by adding 0.3 to 0.95 mass% of graphite with respect to the amount and generating 75 to 95 mass% of 4-basic lead sulfate during aging and drying. Production method.