JP2521064B2 - Lead acid battery anode plate - Google Patents

Description

The present invention relates to an anode plate for a paste-type lead acid battery.

Conventional technology and its problems Although the anode plate of the paste-type lead-acid battery is formed by coating a lead-like grid-like skeleton with a paste-like active substance containing lead oxide, sulfuric acid, and water as main components. In low-rate discharge, the discharge capacity is determined by the active substance, so there is no problem,
There is a drawback that the discharge capacity is greatly reduced in high rate discharge with a large discharge current.

The reason is that in high-rate discharge, the diffusion rate of sulfuric acid is rate-determined, so the discharge capacity is limited by the amount of sulfuric acid inside and in the vicinity of the electrode. It is requested to do.

As a means for improving this, for example, increasing the amount of sulfuric acid or water in the paste, or making it porous with a foaming agent has been studied, but a high-porosity electrode causes a large dropout and a short cycle life. That is the drawback.

As a method for solving these drawbacks, JP-A-56-9137
No. 3 publication is disclosed.

In this Japanese Laid-Open Patent Publication No. 56-91373, a non-woven fabric or a woven fabric is first incorporated into a lattice-shaped skeleton and the paste-like active substance is applied from both surfaces thereof, and the non-woven fabric or the woven fabric is used as an inner layer material of the anode plate. By embedding, the liquid retaining property of sulfuric acid is improved and the supply of the electrolytic solution to the inside is increased.

However, in the published patent of JP-A-56-91373, glass fiber or polyester fiber is used as the material of this non-woven fabric or woven fabric, and these have insufficient hydrophilicity and poor liquid retention and paste adhesion. The degree of inferiority is inferior, and it cannot be said that the structure for supplying the electrolytic solution is satisfactory.

On the other hand, in an anode plate of a lead storage battery, a paste-like active substance is applied to a grid-like skeleton, and a protective film is provided on the surface of the active substance in order to protect the active substance from expansion, shrinkage, weakening, and the like. Although the technology has existed in the past, it has the drawback that when the water content of the pasty active substance is removed, a gap is created between the active substance and the protective film, resulting in poor adhesion and the loss or outflow of the active substance. Of.

Japanese Unexamined Patent Publication No. 60-140651 is disclosed as a means for solving this problem.

In JP-A-60-140651, the above problem is solved by interposing a woven or non-woven fabric between the active substance and the protective film.

That is, by using a woven fabric or a non-woven fabric of the same material as the resin frame used as a part of the lattice-like skeleton as a surface layer material of the active substance, and providing a protective film on the surface of the resin frame, good bonding with the frame is achieved and the fiber layer The elasticity protects the surface of the active substance under pressure, improves the adhesion, and prevents the occurrence of gaps to prevent the active substance from falling off or flowing out.

However, in this Japanese Patent Laid-Open No. 60-140651, a polyethylene non-woven fabric is mainly used because it is a non-woven fabric of the same quality as the resin frame, and the hydrophilicity is poor and the wettability is poor, which causes a negative factor to the ion diffusivity and electric resistance. However, it cannot be said that the battery performance is satisfactory.

The object of the present invention is, as a fiber sheet suitable for the above-mentioned anode plate inner layer material and the above-mentioned anode plate surface layer material, a polyolefin-based synthetic pulp sheet such as polyethylene, which is obtained by adhering and polymerizing a polyfunctional hydrophilic monomer. It intends to solve the above-mentioned problems by considering the use of.

(B) Structure of the invention The structure of the present invention is a lead electrode comprising a grid-like skeleton coated with a paste-like active substance, and a polyolefin-based synthetic pulp sheet obtained by depositing and polymerizing a polyfunctional hydrophilic monomer on an anode plate inner layer material or The present invention is directed to an anode plate for a lead storage battery, which is used as a surface layer material for an anode plate.

Means for Solving Problems Inner layer material as an electrolyte solution source structure for the anode plate, or surface layer material for improving the surface adhesion of the active substance of the anode plate,
An extremely excellent effect can be obtained by using a polyolefin synthetic pulp composed of fibrillated and branched fibers and having improved wettability by treatment with a polyfunctional hydrophilic monomer. I found that.

By the way, the wettability-improved product obtained by treating the polyolefin synthetic pulp sheet such as polyethylene in the present invention with a polyfunctional hydrophilic monomer is a "polyolefin-based wet non-woven fabric" (patented by the applicant in May 1986) Wish
61-115488).

Therefore, the details of the synthetic pulp sheet are as described in the specification of the above-mentioned previous application, and only the summary thereof will be described here.

First, a synthetic pulp made from a polyolefin such as polyethylene as a raw material is produced by a known method, and an aqueous solution containing a polymerization catalyst and a polyfunctional hydrophilic monomer is used as a monomer component in an amount of 2 to 100 parts by weight of the synthetic pulp. It is attached at a ratio of 30 parts by weight and heated and polymerized by steaming or the like.

At least the hydrophilic synthetic pulp thus obtained is
Using 50% or more, acid-resistant glass fiber, polyester fiber, acrylonitrile fiber, polypropylene / polyethylene thin / saya composite fiber, etc. are blended appropriately to obtain a basis weight of 50-150 g / m ² , thickness 0.1- It is a 1 mm non-woven sheet.

As a result, since the fibers of the obtained synthetic pulp sheet are fibrillated, the liquid retaining property is extremely large unlike the simple fibrous substance, and the hydrophobicity of the polyolefin is due to the polymerization treatment of the polyfunctional hydrophilic monomer. Since it is hydrophilized, its liquid retaining property is further improved.

Examples of the polyfunctional hydrophilic monomer that is a hydrophilic agent for the synthetic pulp sheet include polyethylene glycol diacrylate and polyethylene glycol dimethacrylate, and the average number of segments of the polyethylene oxide is 2 to 30. Is preferably used.

In addition to the polyfunctional hydrophilic monomer as the hydrophilizing agent, well-known hydrophilic monomers such as acrylic acid, acrylic amide, itaconic acid, vinylpyrrolidone, and maleic acid may be appropriately used for copolymerization. Of course.

The present invention is most characterized in that the hydrophilic synthetic polyolefin sheet as described above is used as an inner layer material or a surface layer material in an anode plate of a lead storage battery.

FIG. 1 is a longitudinal sectional view of one embodiment of the anode plate of the present invention, showing the case where a polyethylene synthetic pulp sheet is used as an inner layer material.

As shown in this figure, the lead-like lattice skeleton (1) is attached to the inner layer material (2).
And the paste-like active substance (3) containing lead oxide and sulfuric acid is applied from both sides of this, and the inner layer material (2) is sandwiched and held.

Since this inner layer material (2) is the polyethylene synthetic pulp sheet that has been subjected to the hydrophilic treatment as described above, it has an excellent liquid retaining property for the sulfuric acid solution and is very effective as an electrolyte solution source structure. Of. Further, the fibrillated pulp structure and the hydrophilization treatment improve not only the liquid retention but also the adhesion to the paste, and the utility as the inner layer material is further enhanced.

FIG. 2 is a cross-sectional view of another embodiment of the anode plate of the present invention, showing the case where a polyethylene synthetic pulp sheet is used as the surface layer material.

As shown in this figure, the lead-like grid-like skeleton (1) is coated with the same paste-like active substance (3) as described above, and the surface layer material (4) is adhered to the outside thereof, and the surface is further protected. Membrane (5)
Will be provided.

Since the surface layer material (4) is the above-described hydrophilized polyethylene synthetic pulp sheet, it has good wettability and does not adversely affect ion diffusivity and electric resistance, and the elasticity of this sheet also supports expansion and contraction. As a result, the adhesiveness with the paste is improved, and the active substance is prevented from falling off or flowing out.

Example 1 To 100 parts by weight of polyethylene synthetic pulp, 12 parts by weight of an aqueous solution of a polyethylene glycol diacrylate monomer having an ethylene glycol segment number of 15 to which an appropriate amount of ammonium persulfate catalyst was added was adhered as a monomer component by 12 parts by weight, and then steamed. Heat polymerization was carried out in a kettle at 100 ° C. for 1 hour to obtain a hydrophilic synthetic pulp having a polymer adhered by 9.8%.

Next, 75% by weight of this hydrophilic synthetic pulp is mixed with 25% by weight of acid resistant glass fiber having a fiber diameter of 2 to 3 μ,
A sheet material used in the present invention was prepared by making paper with a basis weight of 68 g / m ² and a thickness of 0.3 mm using a 25 cm square test paper machine.

The obtained sheet material is laminated on a lead grid having a size of 50 mm x 60 mm, a lead paste is applied from above, then the grid is turned over and a lead paste is applied from the opposite side, and the sheet material is an inner layer. As a material, a lead electrode arranged in the central portion was created.

In order to investigate the performance of this electrode, the discharge capacity when the discharge current was changed and the effective discharge cycle when the discharge of 5 amps was repeated were measured, and the results are shown in Tables 1 and 2. It was

For comparison with these, the same test as in Example 1 was performed for the case where the sheet material used in the present invention was not used, and the results are shown in Tables 1 and 2 as Comparative Example 1. It was

As is clear from these tables, the lead electrode of the present invention has less decrease in discharge capacity due to high rate discharge as compared with that of the comparative example, and has excellent performance of long life with large charge / discharge cycle. It was a thing.

Example 2 A lead paste was applied to both sides of the same lead grid used in Example 1, and the same sheet material as the sheet material prepared in Example 1 was laminated on both surfaces to form a sandwich structure. A protective film was laminated thereon, and a lead electrode of the present invention having a structure different from that of Example 1 and using a sheet material as a surface layer material was prepared.

In order to investigate the performance of this electrode, the electrical resistance was measured according to JIS-C2313, and the behavior during charging and discharging was also investigated, and the results are shown in Table 3.

For comparison with this, the same test as in Example 2 was carried out on the same sheet material as used in the present invention, which was not subjected to only the hydrophilization treatment. The results are shown.

As is clear from this table, the lead electrode of the present invention has a lower electric resistance than that of the comparative example, and has excellent performance in that no bubbles or short circuits occur during charging and discharging.

C. Effect of the Invention The present invention is as described above, and when a hydrophilized polyolefin synthetic pulp sheet is used as an inner layer material of an anode plate, this layer has an extremely excellent liquid retaining ability, and thus a sulfuric acid solution is used. Is sufficiently retained and also functions as an electrolytic solution supply source, so that the sulfuric acid can be easily supplied even at the time of high-rate discharge, and the discharge capacity can be improved. In addition, since the adhesiveness with the active substance is also good, the anti-falling property is exerted and the cycle life is also brought to a good result.

Also, when a hydrophilic synthetic polyolefin-based pulp sheet is used as the surface layer material of the anode plate, it has excellent wettability and excellent adhesion to the paste which is the anode active substance due to the pulp structure, that is, the fibrillated fiber. Therefore, it does not become a negative factor for ionic diffusivity and electric resistance and also prevents the generation of bubbles, and the elasticity of this synthetic pulp sheet maintains its adhesion even if the anode active material expands or contracts. It has the effect of preventing the active substance from falling off and flowing out.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of the anode plate of the present invention, showing the case where a polyethylene synthetic pulp sheet is used as an inner layer material. FIG. 2 is a cross-sectional view of another embodiment of the anode plate of the present invention, showing the case where a polyethylene synthetic pulp sheet is used as the surface layer material. (1) …… Lattice skeleton, (2) …… Inner layer material, (3) …… Paste-like active substance, (4) …… Surface layer material, (5) …… Protective film

Claims (1)

(57) [Claims] 1. In a lead electrode having a grid-like skeleton coated with a paste-like active substance, a polyolefin-based synthetic pulp sheet obtained by adhering and polymerizing a polyfunctional hydrophilic monomer is used as an anode plate inner layer material or an anode plate surface layer material. An anode plate for a lead-acid battery characterized by being used.