JPH02273461A - Separator for lead-acid battery - Google Patents

Abstract

PURPOSE:To enhance the acid resistance, oxidation resistance and shortcircuit resistance of a separator used for a lead-acid battery without damaging the electrical resistance of the battery and enhance both the low temperature highly efficient discharge performance and life performance of the battery by adding a shortcircuit improving agent and shrink proof agent used for the cathode plate of the lead-acid battery in a predetermined ratio to a porous sheet. CONSTITUTION:A shortcircuit improving agent and a shrink proof agent for the cathode plate of a lead-acid battery are mixed with 100 parts by weight of porous sheets in such a manner that the total amount of addition of both agents are in the range of 0. 5 to 50 parts by weight, the porous sheets each having synthetic fiber of acid resistance, inorganic fiber and inorganic powder as its main components. The shortcircuit improving agent to be applied to the inside or outside of the porous sheet is sulfate, the solubility of which is more than 1g against 100 grammes of water at 20 deg.C. The shrink proof agent is an inorganic material which restrains monocrystal growth of a cathode plate active material, thereby enhancing performance of the cathode plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a separator in lead-acid batteries used in automobiles, electric vehicles, etc.

BACKGROUND ART [0003] Conventional separators for lead-acid batteries are often made of a porous sheet made from acid-resistant inorganic powder and laminated with a dry-processed glass mat.

[Problems to be Solved by the Invention] In the conventional separators for lead-acid batteries as described above, it is extremely difficult to arbitrarily adjust the pore diameter during the manufacturing process, and as a result, variations in pore diameter occur and the separator There were variations in copper oxidation properties and battery life.

By the way, in recent years, separators for automotive lead-acid batteries have been required to have low electrical resistance and excellent acid resistance, oxidation resistance, and short circuit resistance, and conventional separators have become unable to meet these demands. There is.

For example, in order to improve oxidation resistance, attempts have been made to adjust the density by heating and pressurizing the porous sheet, and increasing the amount of binder added, but the oxidation resistance is still poor. However, this does not solve the problem, as the electrical resistance increases, resulting in a decrease in the battery's low-temperature, high-rate discharge performance and capacity.

The purpose of the present invention is to solve the problems mentioned in -1-, and it is possible to improve acid resistance and tm without impairing electrical resistance.
An object of the present invention is to provide a separator for lead-acid batteries that has excellent oxidation and short-circuit resistance, has a good lead penetration prevention effect when the specific gravity of the electrolyte is low, and improves the low-temperature, high-rate discharge performance and life performance of the battery. It is.

[Means for Solving the Problems] As a result of intensive research to achieve the above object, the inventors of the present invention added a short-circuit improver and a shrink-proofing agent for lead-acid battery cathode plates to a porous sheet in a predetermined ratio. It was discovered that very good results could be obtained by doing so.

That is, according to the present invention, a porous sheet containing acid-resistant synthetic fibers, inorganic fibers, and inorganic powder as main components.
The gist of the separator is a separator for lead-acid batteries, characterized in that a short-circuit improver and a shrink-proofing agent for lead-acid battery cathode plates are added in a total amount of 05 to 50 parts by weight. be.

The porous sheet in the present invention is mainly composed of acid-resistant synthetic fibers, inorganic fibers, and inorganic powders, such as 20 to 60 parts by weight of synthetic fibers such as polyethylene, polypropylene, polyacrylonitrile, and polyester, 1 to 10 layers of inorganic fibers such as glass fiber and ceramic fiber, and 3 inorganic powders such as white carphone and diatom 10
0 to 70 parts by weight, and this mixture further contains 1
Polyacrylic acid ester based on 00 parts by weight, SBR
It is obtained by adding 2 to 20 parts by weight of an adhesive such as a type, etc., and making a paper using a wet paper making method.

The separator of the present invention is obtained by adding a short-circuit improver and a shrink-proofing agent for lead-acid battery cathode plates (hereinafter simply referred to as "shrink-proofing agent") in a predetermined ratio by internally and/or externally adding to the porous sheet as described above. It is.

This short-circuit improver is a sulfate such as thorium sulfate, potassium sulfate, magnesium sulfate, and zinc sulfate.
Those having a solubility of 1 g or more per 100 g of water at 20'C can be suitably used.

These short-circuit improvers are additives that have been conventionally known as additives that are added to the electrolyte to suppress short-circuits through the separator of dendritic lead when the specific gravity of the electrolyte is low. Therefore, we attempted to incorporate this electrolyte additive into a separate lake.

Further, the shrink-proofing agent in the present invention is a lignin-based organic substance and an inorganic substance such as barium sulfate or strontium sulfate.

This anti-shrink agent is originally an additive added to the active material in order to suppress the growth of single crystals in the cathode plate active material and therefore improve the performance of the cathode plate. It was blended into

For boat fishing, barium sulfate is effective in extending the cycle life, and lignin is known to have the effect ψ2 of increasing worn-out clothes during large current discharge at low temperatures.

In the present invention, the total amount of the short-circuit improver and shrink-proofing agent added is O15 to 5 with respect to 100 parts of the porous sheet.
It is required that the melting point is 0, and if it is less than 0.5, the active substance inside the porous sheet is leached out enough to provide short-circuit resistance and shrinkage prevention effect to the active material at the contact surface with the cathode plate. Since the concentration cannot be obtained and the absolute amount is small, the sustainability of the effect is poor, and the life of the separator cannot be extended. - If the total amount added exceeds 50 parts by weight, the electrical resistance of the porous sheet becomes higher than that without additives, and the elution concentration of the active substance into the electrolyte tends to increase. Internal self-discharge becomes more likely to occur, resulting in a decrease in battery capacity, which defeats the original purpose of the battery.

The total amount of the short-circuit improver and shrink-proofing agent added is as described above, but the mixing ratio of each is set so that the ratio of short-circuit improver to shrink-proofing agent is in the range of 1:0.01 to 1:70. A suitable result can be obtained by mixing it with the following.

This ratio is 1. : If it is less than 0.01, there will be too little shrink-proofing agent, and the shrink-proofing effect of the active material at the contact surface between the porous sheet and the cathode plate will be poor. On the other hand, if this ratio exceeds 1=70, the amount of the short-circuit improver will be too small, and no improvement in short-circuit resistance will be observed when the specific gravity of the electrolyte is low.

If the ratio of the short improver and anti-shrink agent is within the above range,
This makes it possible to extend the life of the separator sufficiently in response to changes in the specific gravity of the electrolytic solution.

The separator for lead-acid batteries of the present invention is a sheet-like material made of the following main materials, additives, and their appropriate blending ratios, or, if necessary, other auxiliary materials 1, such as alkylsulfonic acid. Of course, a surfactant such as soda may be added.

The method for producing a separator for lead-acid batteries according to the present invention may use a porous sheet forming method using a circular wire machine or a fourdrinier machine, and a short-circuit improver and a shrink-proofing agent are internally added during the paper-forming process. Or/and externally added to obtain the separator of the present invention.

Next, a method for making a separator and a method for adding additives in the present invention will be explained.

First of all, a means for adding both the short improver and the anti-shrink agent by internal addition will be shown.

In this case, a predetermined amount of fiber material is dispersed in water using a beater or pulper, then predetermined amounts of inorganic powder, short-circuit improver, and anti-shrink agent are added and dispersed uniformly. After adding other auxiliary materials in predetermined amounts according to the conditions, and then adding a predetermined amount of fixing agent to fully deposit the adhesive into the mixture, the dispersed slurry is stirred relatively slowly. Direct it to the chiest and use a flocculant if necessary to maintain uniform dispersion.

At the same time, it is guided to a round net paper making section or a Fourdrinier paper making section and is made into a wet sheet. Then, the separator of the present invention can be obtained by introducing it into a drying section and drying it.

In addition, when this porous sheet is made into a multilayered structure, this method of internal addition allows the active substance to be added to any position in the multilayered structure, and the properties of the added substance It is only necessary to select the layer to be applied according to the effect of the anti-shrink agent, for example, barium sulfate, which has low solubility in the electrolytic solution, is desirably applied to the surface layer in contact with the cathode plate.

Second, a method is shown in which an anti-shrink agent is added internally and a short-circuit improver is added externally.

In this case, a porous sheet is created by internally adding only an anti-shrink agent in the same manner as above, and then an aqueous solution containing a short-circuit improver dissolved at a predetermined concentration is impregnated into this porous sheet and dried to improve short circuits. The agent is externally added to the separator of the present invention.

For example, at a position 50 to 150μ below the surface of the separator,
After blending an anti-shrink agent by an internal addition method and forming a layer fixed with a binder, this sheet is coated with a short-circuit improving agent of 0.3 to
Immerse it in an aqueous solution containing 40% by weight, squeeze it out, and dry it until it reaches a weight within the above range! - Adding improvers.

The separator of the present invention obtained by internally adding this anti-shrink agent and externally adding a short-circuit improving agent exhibits excellent effects as explained in the function section below.

The third method is to add both the anti-shrink agent and the short-circuit improver by external addition.

In other words, depending on the type of shrink-proofing agent, it can be added externally in the same way as the short-circuit improving agent. Specifically, the short-circuit improving agent and the shrink-proofing agent can be added externally to the porous sheet formed as described above. The separator 1/1 of the present invention is introduced into a dissolution tank containing an aqueous solution adjusted to a concentration and impregnated with the aqueous solution, and then dried.
-ta can be obtained.

In addition, when the additives are externally added in this manner, effects unique to this method can be obtained, as will be explained in the section below on effects.

The means for blending additives in the separator of the present invention is "2, 3.
It is not limited to the above, and may be added externally to J2 which has been added internally. For example, an anti-shrink agent can be added internally and a short-circuit improver can be added both internally and externally, and the anti-shrink agent can also be added to improve short-circuits. Both agents may be added by internal or external addition.

As described above, the method of adding the shrink-proofing agent and the short-circuit improving agent in the present invention is not limited to internal addition or external addition, but as mentioned above, the key point is to incorporate such additives and the amount of addition. This is a major feature.

[Function] The separator of the present invention has the above-mentioned structure, and when it is applied to a lead-acid battery, it is used in a multilayered manner with a glass mat layer manufactured by a wet continuous papermaking method, and this multilayered material is is arranged between the electrode plates in a lead-acid battery.

In this case, the crow mat is placed in contact with the anode surface and the separator is placed in contact with the cathode surface.

When coordinated in this manner, the antishrink agent fixed to the inner layer of the separator with a binder gradually dissolves over time on the cathode surface of the separator, and is adsorbed on the cathode surface, increasing the effect of inhibiting crystal growth. I was able to confirm this.

In addition, it was confirmed that the improver added to the separator of the present invention also eluted over time, and that this improved the effect of preventing lead penetration when the specific gravity of the electrolytic solution was low.

It is preferable to incorporate this anti-shrink agent into the inner layer of the separator because it gradually dissolves out. Therefore, it is preferable to make the separator into a multi-layered structure and add it internally to the second or third layer from the surface layer. On the other hand, even if the shell improver is incorporated into the entire layer, it will gradually dissolve from the surface layer, so it is better to add it by external means.

Therefore, it is desirable that the second addition means, that is, the anti-shrink agent be added internally, and the short improver be added externally.

In addition, in the separator of the present invention obtained by the above-mentioned third method, that is, the method of externally adding both the shrink-preventing agent and the short-circuit improving agent, the oxidation resistance of the separator base material is significantly improved as an effect other than the above. This has the effect of significantly reducing oxidative deterioration of the separator base material after the oxidation resistance test.

As can be seen from the above description, the separator for lead-acid batteries of the present invention not only achieves improved performance as a separator, but also improves battery performance due to the shrinkage effect of the cathode active material inside the battery. It is something that can be obtained.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited in any way by this example.

[Example] The main material of the porous sheet and its manufacturing method were unified as follows.

Acrylic fiber 1120 with a thickness of 3 denier and a length of 5 mm
Part by weight, 30 parts by weight of synthetic fibers with a water content of 2, and 5 parts by weight of glass fiber H with a fiber diameter of 1, and an amorphous inorganic powder with a specific surface area of 200 m'/g. Using 40 parts by weight of silica, and further using 5 parts by weight of acrylic acid ester synthetic resin as an adhesive, all of these (100 parts by weight in total) were uniformly dispersed with a pulper, and 3 parts by weight with a round netting machine. After layer-forming, it was dried to obtain a porous sheet with a thickness of 0.3 mm and a basis weight of 100 g/m'.

Based on the production of the porous sheet described above, the following seven types of anti-shrink agents and short-circuit improvers were added to 100 parts by weight of this porous sheet.

In all of the seven examples listed in F, the shrink-proofing agent was added to the second layer by internal addition, and the short-circuit improver was added to the second layer by external addition.

Example 1 0.05 parts by weight of barium sulfate and 0.05 parts by weight of lignin as anti-shrink agents were mixed with a binder in the second layer from the cathode side to t4ioo parts by weight of the main material of a three-layer porous sheet. Dry.

In the - method, +-i sodium sulfate is used as a short-circuit improver, and the dried porous sheet is introduced into a tank containing a 0.1% aqueous solution of sodium sulfate, and the solution is mixed with a
By impregnating and drying at a ratio of g/m', 0.1 part by weight of a short-circuit improver was externally added to 100 parts by weight of the main material of the porous sheet, and a separator for lead-acid batteries was prepared.

In addition, in this Example 1, the total amount of the shrink-proofing agent and the short-circuit improving agent was 0.2 parts by weight, and the porous sheet 1-], O
It is less than 35 parts by weight of O compared to 0 parts by weight, which is a comparative example in which the amount added is too small.

Example 2 As in Example 1, 0.3 parts by weight of barium sulfate and 0.3 parts by weight of lignin were mixed in the second layer, and the dried sheet was treated with sodium sulfate as a short improver in the same manner as in Example 1. It was introduced into a tank containing a 0.4% by weight aqueous solution, impregnated with about 100 g/m' of the solution, dried, and externally added in an amount of 0.4 parts by weight.
A separator for lead-acid batteries was obtained.

Example 3 The barium sulfate in Example 1 was changed to 2 parts by weight, the lignin was changed to 2 parts by weight, and the concentration of the sodium sulfate aqueous solution in Example 1 was changed to 2% by weight, and all other conditions were the same as in Example 1. A separator for lead-acid batteries was obtained in the same manner.

Example 4 A separator for a lead-acid battery was produced in the same manner as in Example 1 except that barium sulfate and lignin in Example 1 were each changed to 4 parts by weight, and the concentration of sodium sulfate in Example 1 was changed to 10% by weight. Obtained.

Example 5 The barium sulfate and lignin in Example 1 were each changed to 7 parts by weight, the concentration of sodium sulfate in Example 1 was changed to 16% by weight, and everything else was the same as in Example 1 to prepare a separator for lead-acid batteries. Got I/- evening.

Example 6 A lead-acid battery was prepared in the same manner as in Example 1 except that the barium sulfate and lignin in Example 1 were each changed to 5 parts by weight, and the concentration of barium sulfate in Example 1 was changed to 35 double star. I obtained a separator for this purpose.

Note that Examples 2 to 6 correspond to Examples of the present invention.

Example 7 A separator for lead-acid batteries was prepared in the same manner as in Example 1 except that the barium sulfate and lignin in Example 1 were each changed to 25 parts by weight, and the concentration of sodium sulfate in Example 1 was changed to a 10-fold star. And so.

In addition, in this Example 7, the total amount of the shrink-proofing agent and Shaw 1-improving agent added was 60 parts by weight, which exceeded 50 parts by weight based on 100 parts by weight of the porous sheet, which was too large. This is a comparative example.

Regarding the seven examples below-1-, the porous sheet 10
Table 1 summarizes the amounts of the short improver and anti-shrink agent added to 0 parts by weight and their addition ratios.

*The short-circuit improver is sodium sulfate, and the anti-shrink agent uses both ligrin and barium sulfate, with a weight ratio of 1:1.

Tables 2 and 3 show the characteristics of the separators prepared in these seven examples and the results of the battery performance comparison test.

However, these evaluations were made in comparison with an additive-free product to which no improver or anti-shrink agent was added.

Table 2 After completion of energization, the separator was dismantled and the presence or absence of lead penetration into the separator was confirmed, and the lowest value of the electrolyte specific gravity at which lead penetration was not observed was defined as the shot resistance limit specific gravity.

In addition, the test for the short-circuit limit specific gravity was conducted by the following method.

Insert a separator between the 5cm square ship type plates, and insert 20cm
After applying a load of Kg/100cJ and then injecting an electrolytic solution adjusted to a predetermined specific gravity, 1.6 A,/
], energize for 1 hour at a current value of OOcl.

From Tables 2 and 3, it can be seen that in Examples 2 to 6, which correspond to the examples of the present invention, IN)t acid.
It is recognized that the oxidation resistance and short-circuit resistance are excellent, and that the battery performance is improved in both low-temperature high-rate discharge performance and life performance.

[Effects of the Invention] The effects of the present invention are that it has excellent antacid/acidification resistance and short-circuit resistance without impairing electrical resistance, has a good effect of preventing lead penetration when the specific gravity of the electrolyte is low, and can be used at low temperatures as a battery. The company has provided a separator for lead-acid batteries that improves high-rate discharge performance and life performance, and is able to meet the recent demands of the industry and exhibits extremely high usefulness. It is.

Claims (1)

[Claims] 1. For 100 parts by weight of a porous sheet mainly composed of acid-resistant synthetic fibers, inorganic fibers, and inorganic powder,
A separator for a lead-acid battery, characterized in that a short-circuit improver and an anti-shrink agent for a lead-acid battery cathode plate are blended in a total amount of 0.5 to 50 parts by weight. 2. The separator for lead-acid batteries according to claim 1, wherein the ratio of the short-circuit improver to the shrink-proofing agent for lead-acid battery cathode plates is in the range of 1:0.01 to 1:70.